Claims:1. A cost effective process for the preparation of Molnupiravir of Formula 1,


Formula 1
comprising;
i. Reacting cytidine (Formula 5) with 2,2 diemthoxypropane in presence of mineral acid selected from hydrochloric acid or nitric acid to obtain 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydro furo [3,4-d] [1,3]dioxol-4-yl) pyrimidin-2(1H)-one (Formula 4);

Formula 4
ii. Esterifying 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one of Formula 4 with isobutyric anhydride in presence of 1,8-diazabicyclo[5.4.0]undec-7-ene and phase transfer catalyst in non-aqueous chlorinated solvent to obtain((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3);

Formula 3
iii. Hydroxyaminating ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate intermediate of Formula 3 with reducing agent selected from hydroxylamine hydrochloride in aqueous polar solvents and in inorganic base to obtain ((3aR,4R,6R,6aR)-6-(4-(hydroxylamino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3] dioxol-4-yl) methyl isobutyrate (Formula 2) .

Formula 2
iv. Deprotecting/De-alkylating ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3] dioxol-4-yl) methyl isobutyrate of Formula 2 with acid selected from sulphuric acid, hydrochloric acid, trifluoro acetic acid or para toluene sulfonic acid in aqueous polar solvents to obtain ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yltetrahydrofuran-2-yl) methyl isobutyrate, i.e. Molnupiravir (Formula 1).

2. The process as claimed in claim 1, step (i), wherein the solvent is selected from polar organic solvents, such as acetone, acetonitrile, isopropyl alcohol, methanol or ethanol alone or mixtures thereof.

3. The process as claimed in claim 1, step (i), wherein the process may be carried out in presence of the catalyst selected from iodine or 5% molybdenum(VI) dichloride dioxide .
4. The process as claimed in claim 1, step (ii), wherein the phase transfer catalyst is selected from the group consisting of tetra butyl ammonium bromide or tri ethyl benzyl ammonium chloride.
5. The process as claimed in claim 1, step (ii), wherein the chlorinated solvent is selected from dichloromethane, ethylene dichloride, chloroform alone or mixtures thereof.
6. The process as claimed in claim 1, step (iii), wherein the inorganic bases for maintaining pH of reaction system is selected from ammonia solution, sodium hydroxide or potassium hydroxide.
7. The process as claimed in claim 1, step (iii), wherein the aqueous polar solvent is selected from the group consisting of isopropyl alcohol, acetonitrile, methanol, ethanol alone or mixtures thereof.
8. The process as claimed in claim 1, step (iv), wherein the aqueous polar organic solvent(s) is selected from the group consisting of acetonitrile, ethyl acetate, isopropyl alcohol, methanol, ethanol alone or mixtures thereof.
9. The process as claimed in claim 1, step (iv), wherein the inorganic bases for maintaining pH of reaction system is selected from ammonia solution, sodium hydroxide or potassium hydroxide.
10. The process as claimed in claim 1, step (iv), wherein the process may be carried out in presence of catalyst selected from zirconium tetrachloride or indium trichloride.
11. The process as claimed in claim 1, wherein the reduction step (iii) and the deprotection step (iv) may be carried out in-situ.

12. The process as claimed in claim 11, wherein the in-situ process comprises;

(i) Preparing the intermediate compound 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydrofuro [3,4-d] [1,3]dioxol-4-yl) pyrimidin-2(1H)-one (Formula 4) from cytidine as claimed in step (i) of claim 1;
(ii) Preparing ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3] dioxol-4-yl)methyl isobutyrate (Formula 3) by the process as claimed in step (ii) of claim1;
(iii) Adding the reducing agent selected from hydroxylamine hydrochloride in aqueous polar solvents and in presence of base to the intermediate compound of Formula 3 to yield Molnupiravir (Formula 1);
13. The process as claimed in claim 12, step (iii) wherein the suitable inorganic bases for maintaining pH of reaction system is selected from ammonia solution, sodium hydroxide or potassium hydroxide.
14. The process as claimed in claim 12, step (iii), wherein the aqueous polar organic solvent(s) is selected from acetonitrile, ethyl acetate, isopropyl alcohol, methanol, ethanol alone or mixtures thereof.
, Description:FIELD OF THE INVENTION
The present invention relates to a novel process for the preparation of Molnupiravir (Formula-1),. More particularly, the invention relates to a novel process for the synthesis of Molnupiravir with increased efficiency in terms of yield.

BACKGROUND OF THE INVENTION
Molnupiravir (EIDD-2801/MK-4482) is an investigational, orally bioavailable form of a potent ribonucleoside analog that inhibits the replication of multiple RNA viruses including SARS-CoV-2, the causative agent of COVID-19. Molnupiravir has been shown to be active in several models of SARS-CoV-2, including for prophylaxis, treatment, and prevention of transmission, as well as SARS-CoV-1 and MERS.

Molnupiravir (MK-4482, EIDD-2801) is in development by Merck after licensing from Ridgeback Biopharmaceuticals as an orally dosed antiviral for the treatment of COVID-19. Animal studies have shown successful inhibition of SARS-CoV-2 as well as prevention of viral transmission. It proves to be safe and effective in ongoing clinical trials. This drug would be important to encounter SARS-CoV-2 virus pandemic, hence it will be useful for treating non-hospitalized patients with laboratory-confirmed COVID-19.

As density of the population is quite high in many cities in India, control of the spread of COVID-19 remains challenging. Even after the pandemic subsides, there is a possibility of a resurgence of COVID-19 at any time. In order to be prepared for the treatment of novel coronavirus or other viruses at a future date is also extremely important. The quantum of drugs required is quite huge and challenging for commercial-scale production especially for active pharmaceutical ingredients (APIs) like Molnupiravir which involves complex chemistry. Therefore, the development of cost-effective process is the need of the hour for the synthesis of API, Molnupiravir to cater to the demand in India and the rest of the world. Moreover, India is among very few countries in the world that produces APIs and always takes responsibility to provide APIs to other pharmaceutical producers of the world during any crisis or epidemic. Therefore, there exists a huge need and potential for the commercialization of API Molnupiravir.

WO2019173602-discloses 4’-halogen containing nucleotide and nucleoside therapeutic compositions and uses related thereto. WO’602 explains derivatives of 4’-halogen nucleosides optionally conjugated to a phosphorus oxide or salts thereof, prodrugs or conjugate compounds or salts thereof comprising an amino acid ester, lipid or a sphingolipid or derivative linked by a phosphorus oxide to a nucleotide or nucleoside. Following is the general Formula:

WO2019113462 discloses a preparation method of a synthesis of Molnupiravir (EIDD-2801) by protection, esterification, triazolation, deprotection of Uridine to obtain desired product.

CN112608357 discloses a process for production of Molnupiravir by reacting Cytidine based intermediate with co-enzyme. It is basically bio-catalyzed esterification reaction, carried out in micro–channel reactor to obtain Molnupiravir.

CN112552288 discloses a process of preparation method of 4-Oxime-s’(2-methylpropionyl) uridine and Molnupiriavir .

The article titled “A Concise Route to MK-4482 (EIDD-2801) from Cytidine: Part 2” by V. Gopalsamuthiram et al. published in Synlett 2020, 31, A–C, DOI: 10.1055/a-1275-2848; Art ID: st-2020-v0498-l disclose the process for preparation of Molnupiravir from cytidine as depicted in the scheme below:

The processes for the synthesis of Molnupiravir disclosed therein in the cited prior arts do not provide cost-effective process on a commercial scale for the synthesis of Molnupiravir.

Further handling of reagents and biocatalyst is difficult; reaction is carried out at micro scale level which is not commercially viable. Also, the efficiency in terms of yield of the process of the cited prior arts is comparatively low.
The present inventors felt that there is a scope to provide a more industrially feasible chemical process for the synthesis of Molnupiravir by employing reaction conditions which would be more feasible on commercial scale as compared to the process disclosed by V. Gopalsamuthiram et al.

In view of the above, the present inventors have devised a process that can be extended successfully to accomplish a highly efficient process with a high yield of Molnupiravir. The process needs to take into consideration to avoid bio-catalyst (enzymes) as reported in the cited prior arts. The use of economical raw materials with less number of reaction steps contributes towards better yield and sustainable product can be offered on a commercial scale.

OBJECTS OF THE INVENTION
The main object of the present invention is to provide a novel process for the synthesis of Molnupiravir using low cost reagents and also to provide a convenient economical process for preparation of high-quality compound, with increased efficiency in terms of yield.

Another object of the present invention is to provide a process using chemical reaction and environment-friendly reagents which are cost effective, does not use expensive bio-catalyst enzyme and increases the overall reaction efficiency in terms of yield of Molnupiravir , as well as the reaction time cycle is shortened.

SUMMARY OF THE INVENTION
In accordance with the above objectives, the present invention provides a process for the synthesis of Molnupiravir using low cost raw material and reagents with increased efficiency in terms of yield.

In an aspect, the present invention provides a cost effective process for synthesis of Molnupiravir (Formula 1)comprising;

Formula 1
i. Reacting cytidine (Formula 5) with 2,2 diemthoxypropane in presence of mineral acid selected from hydrochloric acid or nitric acid to obtain 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydrofuro [3,4-d] [1,3]dioxol-4-yl) pyrimidin-2(1H)-one (Formula 4);

Formula 4

ii. Esterifying the intermediate compound of Formula 4 with isobutryic anhydride in presence of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and phase transfer catalyst in non-aqueous chlorinated solvent to obtain ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3);

Formula 3
iii. Hydroxyaminating the compound of Formula 3 with reducing agent selected from hydroxylamine hydrochloride in aqueous polar solvents and in presence of base to obtain (3aR,4R,6R,6aR)-6-(4-(hydroxylamino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2);

Formula 2

and
iv. De-alkylating/Deprotecting the intermediate compound of Formula 2 with acid in aqueous polar solvents to yield Molnupiravir (Formula 1);

In another aspect of the present process, the step (iii) of hydroxyamination of the compound of Formula 3 and deprotection/ dealkylation (step iv) with acid to yield Molnupiravir, may be performed “in-situ”. The “in-situ” process results in obtaining better yield of final product with drastic reduction in the reaction time cycle.

The present invention provides a process using environment-friendly reagents which are cost effective; does not use expensive bio- catalyst, and increases the overall reaction efficiency in terms of yield of the final product, Molnupiravir.

DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in detail in its preferred and optional embodiments so that the various aspects therein can be more clearly understood and appreciated.

In an embodiment, the present invention relates to a cost effective process for synthesis of Molnupiravir, comprising;
i. Reacting cytidine (Formula 5) with 2,2 diemthoxypropane in presence of mineral acid selected from hydrochloric acid or nitric acid to obtain 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydrofuro [3,4-d] [1,3]dioxol-4-yl) pyrimidin-2(1H)-one (Formula 4);

ii. Esterifying the intermediate compound of Formula 4 with isobutryic anhydride in presence of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and phase transfer catalyst in non-aqueous chlorinated solvent to obtain ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methylisobutyrate (Formula 3);

iii. Hydroxyaminating the compound of Formula 3 with reducing agent selected from hydroxylamine hydrochloride in aqueous polar solvents and in presence of base to obtain (3aR,4R,6R,6aR)-6-(4-(hydroxylamino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2);

iv. De-alkylating/Deprotecting the intermediate compound of Formula 2 with acid in aqueous polar solvents to yield Molnupiravir (Formula 1);

The step (i) of alkylation of cytidine may be carried out in presence of catalyst 5% molybdenum(VI) dichloride dioxide or iodine.

The phase transfer catalyst employed in the process step (ii) comprising esterification of the compound of Formula (4) includes but is not limited to 4-dimethylamino pyridine, tetra butyl ammonium bromide, triethyl benzyl ammonium chloride and the like. The solvent is selected from non-aqueous chlorinated solvent like dichloromethane, ethylene dichloride, chloroform either alone or mixtures thereof.

In the process step (iii) the aqueous polar solvents include but is not limited to acetonitrile, isopropyl alcohol, methanol, ethanol and the like either alone or mixtures thereof. The suitable inorganic bases used for maintaining pH of reaction system is selected from ammonia solution, sodium hydroxide or potassium hydroxide.

The deprotection step (iv) of the present process is carried out with the acid selected from sulphuric acid, hydrochloride acid, trifluoro acetic acid, para toluene sulfonic acid, formic acid and the like either alone or mixtures thereof. The process of deprotection may optionally be carried out in presence of catalysts such as zirconium tetrachloride or indium trichloride. The aqueous polar solvents include but is not limited to acetonitrile, isopropyl alcohol, methanol, ethanol and the like either alone or mixtures thereof. The base for maintaining the pH of the solution to neutral is selected from inorganic base such as ammonia solution, sodium hydroxide or potassium hydroxide.

In an embodiment, of the present process, the step (iii) of hydroxyamination and deprotection/dealkylation of the compound of Formula 3 to yield Molnupiravir, may be performed “in-situ”. The “in-situ” process results in obtaining better yield of final product with drastic reduction in the reaction time cycle.

In the “in-situ” process since pH of the reaction mass is above 4-5, from the hydroxyamination step, HCl is liberated from hydroxylamine hydrochloride which is consumed for deprotection step. Hence addition of acid is not required.
The process steps of the present invention will now be described in detail herein below:
Step (i): To the solution of cytidine (Formula 5) in acetone prepared under ambient temperature was added 2,2-dimethoxypropane and the mixture was stirred to obtain homogeneous solution. Mineral acid selected from sulphuric acid, hydrochloric acid or nitric acid was added at ambient temperature and the reaction mass was slowly heated until completion of the reaction. After reaction completion, triethyl amine was added at ambient temperature. The reaction mass was cooled slowly over time period then chilled to obtain the solid, 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydrofuro[3,4-d] [1,3] dioxol-4-yl) pyrimidin-2(1H)-one (Formula 4) which was filtered, washed and dried under vacuum.

In the process step 1, the reaction may be carried out in presence of catalyst using 5% molybdenum(VI) dichloride dioxide in methanol or iodine.
The product was obtained in high yield and with HPLC purity >98%.
Step (ii): The intermediate compound 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydro furo[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one (Formula 4) of step (i) was dissolved in non-aqueous chlorinated solvent to obtain the homogenous solution. 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and suitable catalysts selected from 4-dimethylamino pyridine, tetra butyl ammonium bromide or tri ethyl benzyl ammonium chloride was added in reaction mass slowly under nitrogen atmosphere. The reaction mixture was cooled and then slowly added isobutyric anhydride drop wise under nitrogen atmosphere. The reaction mass was stirred and chilled. Quenching of reaction mixture was carried out slowly into ice water followed by extraction in suitable solvent. The organic layer was separated, washed and dried. The insoluble fraction was filtered off and the content ratio of the solvent was decreased by way of distillation up to 70 to 80%. To the mixture was added aliphatic or aromatic hydrocarbon such as hexane, heptane, toluene or xylene alone or mixtures thereof and the reaction mass was chilled. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3) was filtered, washed and dried under vacuum.

The product was obtained in high yield and with HPLC purity >98%.
Step (iii): The solution mixture of hydroxylamine hydrochloride in suitable solvent was stirred at ambient temperature. The reaction mass was chilled and pH was adjusted to 7 to7.5 by using a base selected from liq ammonia solution (30%) or alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. Stirred the mixture and the reaction mass was chilled. The intermediate compound ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetra hydro furo[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3) was added slowly. Water was further added to the reaction mass and cooled The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl) methylisobutyrate (Formula 2) was filtered, washed and dried .

The product was obtained in high yield and with HPLC purity >98%.
Step (iv) : To the intermediate compound ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2) was added suitable solvent at ambient temperature followed by addition of acid and the mixture was heated. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7–7.5 by the addition of inorganic base selected from liq. ammonia, sodium hydroxide or potassium hydroxide and stirred. The reaction mixture was further heated, washed with solvent and the solvent were removed by means of vacuum distillation up to 50-60%. The reaction mass was further washed with water, and the aqueous layer extracted with solvent. The insoluble fraction was filtered off and the content ratio of the solvent was decreased by way of distillation up to the moisture content NMT 1.0%. The reaction mass was further heated and cooled. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed and dried under vacuum.

The process of deprotection may be carried out in presence of catalyst such as zirconium tetrachloride or indium trichloride.

In the alternate embodiment of the present process the steps of hydroxyamination of the intermediate compound of Formula 3 and dealkylation or deprotection was carried out in one pot.

Accordingly the process step comprises dissolving hydroxylamine hydrochloride in suitable solvent at ambient temperature. Chilled the reaction mass. The intermediate compound ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate of Formula 3 was added slowly and the reaction mass was stirred until completion of the reaction. After reaction completion, the obtained mixture was heated, cooled to ambient temperature and neutralized to obtain pH = 7 – 7.5 by the addition of suitable base. The reaction mixture was further heated and the solvent traces were removed by means of vacuum distillation. Suitable solvent was further added to the reaction mass which was removed under vacuum distillation. The reaction mass was washed with water, extracted in solvent and dried. The insoluble fraction was filtered off and the content ratio of the solvent was decreased by way of distillation up to the moisture content NMT 1.0%. The reaction mass was further heated cooled and then chilled. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl) tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed and dried under vacuum.

In an embodiment of the “in-situ” process since pH of the reaction mass is above 4-5, from the hydroxyamination step, HCl is liberated from hydroxylamine hydrochloride which is consumed for deprotection step. Hence addition of acid is not required.

The “in-situ” process results in obtaining better yield of final product with drastic reduction in the reaction time cycle.

The present invention provides a process using low cost raw material and reagent which make the process cost effective and sustainable. Process does not require costly biocatalyst, enzyme, as well as the time of the reaction is shortened. Further isolation of intermediates are easy, no side reaction and byproducts are formed during reaction which help in increasing overall reaction efficiency in terms of yield of Molnupiravir.

The process of the present invention uses mild reaction conditions, simple and convenient operation, easy separation for product and low cost reagents having lower environmental impact, reduced amount of by-product and impurities, lower investment cost, does not use expensive catalyst, as well as the time of reaction is shortened and increases the overall reaction efficiency in terms of yield of Molnupiravir. The process of the present invention is industrially scalable and can be used to prepare Molnupiravir on commercial scale.

The process is further described by the following non-limiting examples, which provides the preferred mode of carrying out the process of the present invention. It is to be appreciated that several alterations, modifications, optimizations, alternations of the processes described herein are well within the scope of a person skilled in the art and such alterations, modifications, optimizations, alternations, etc. should be construed to be within the scope of the present inventive concept as is disclosed anywhere in the specification.

Example 1: Synthesis of the intermediate 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one.(Formula 4).
A solution of cytidine (100g) in acetone (600 mL) was prepared at ambient temperature. The reaction mixture was allowed to stir for 30 minutes at ambient temperature to get homogeneous solution. The solution of 2,2-dimethoxypropane (45g) was added slowly to the stirred solution of cytidine acetonide to obtain homogenous solution. Sulfuric acid (0.5g) was added at ambient temperature. The reaction mass was slowly heat 52-58°C over time period of 2 hours. The reaction mixture was further stirred for 4 hours at 52-58°C. After reaction completion, Triethyl amine (1.5g) was added at ambient temperature. The reaction mass was cooled to 25-30°C slowly over time period of 1.0-2.0 hrs then chilled to 0-5°C. The solid obtained is 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydro furo[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one which was filtered, washed with acetone, and dried at 30-35°C under vacuum.
Yield: 130g, HPLC Purity > 98 %

Example 2: Synthesis of the intermediate 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one. (Formula 4).

A solution of cytidine (100g) in acetone (800 mL) was prepared at ambient temperature. The reaction mixture was allowed to stir for 15 minutes at ambient temperature to get homogeneous solution. The solution of 2,2-dimethoxypropane (60g) was added slowly to the stirred solution of cytidine acetonide to obtain homogenous solution. Hydrochloric acid (5g) was added at ambient temperature. The reaction mixture was further stirred for 10 hours at 70-80°C. After reaction completion, Triethyl amine (2.0g) was added at ambient temperature. The reaction mass was cooled to 25-30°C slowly over time period of 1.0-2.0 hrs then chilled to 0-5°C. The solid obtained is 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydro furo[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one which was filtered, washed with acetone, and dried at 30-35°C under vacuum.
Yield: 131g, HPLC Purity > 98 %.

Example 3: Synthesis of the intermediate 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2 (1H)-one. (Formula 4).

A solution of cytidine (100g) in acetone (750 mL) was prepared at ambient temperature. The reaction mixture was allowed to stir for 30 minutes at ambient temperature to get homogeneous solution. The solution of 2,2-dimethoxypropane (55g) was added slowly to the stirred solution of cytidine acetonide to obtain homogenous solution. 5% molybdenum(VI) dichloride dioxide (1.25g) in methanol (25ml) was added at ambient temperature. The reaction mass was slowly heated to 52-58°C over time period of 2.0 hours. The reaction mixture was further stirred for 4 hours at 52-58°C after reaction completion, Triethyl amine (2.5g) was added at ambient temperature. The reaction mass was cooled to 25-30°C slowly over time period of 1.0-2.0 hrs then chilled to 0-5°C. The solid obtained is 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydro furo[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one which was filtered, washed with acetone, and dried at 30-35°C under vacuum.
Yield: 126g, HPLC Purity > 98 %

Example 4: Synthesis of the intermediate 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one. (Formula 4).

A solution of cytidine (100g) in acetone (800 mL) was prepared at ambient temperature. The reaction mixture was allowed to stir for 30 minutes at ambient temperature to get homogeneous solution. The solution of 2,2-dimethoxypropane (50g) was added slowly to the stirred solution of cytidine acetonide to obtain homogenous solution. Nitric acid (2.5g) was added at ambient temperature. The reaction mass was slowly heated to 55-60°C over time period of 3 hours. The reaction mixture was further stirred for 6 hours at 55-60°C. After reaction completion, Triethyl amine (5g) was added at ambient temperature. The reaction mass was cooled to 25-30°C slowly over time period of 1.0-2.0 hrs then chilled to 0-5°C. The solid obtained is 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyl tetrahydro furo[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one which was filtered, washed with acetone, and dried at 30-35°C under vacuum.
Yield: 127g, HPLC Purity > 98 %

Example 5: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3).
The reaction intermediate, 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one (100g) of formula 4 in methylene dichloride (1000ml) was stirred at ambient temperature to get homogeneous solution. 1,8-diazabicyclo[5.4.0]undec-7-ene (50g) and 4-dimethylaminopyridine (2.25g) was added in reaction mass slowly under nitrogen atmosphere. The reaction mixture was cooled to 0-5°C and then slowly added isobutyric anhydride (65g) drop wise under nitrogen atmosphere. The reaction mixture was stirred at 25 to 30°C for 14 hrs. The reaction mass was chilled to 0 to 5°C. Quenching of reaction mixture was then done slowly into ice water and then the reaction mass was extracted with methylene dichloride [250 mL x 3 times] and the organic layer was separated. The organic layer was then washed with water and was dried over sodium sulphate bed. The insoluble fraction was filtered off and the content ratio of methylene dichloride was decreased by way of distillation up to 70%. After that added heptane 100 ml and the reaction mass was chilled to 0-5°C. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with heptane, and dried at 50-55°C under vacuum.
Yield: 82g, HPLC Purity > 98%.

Example 6: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3).

The reaction intermediate, 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one (100g) (Formula 4) in methylene dichloride (1200ml) was stirred at ambient temperature to get homogeneous solution. 1,8-diazabicyclo[5.4.0]undec-7-ene (25g) and 4-dimethylaminopyridine (4g) was added in reaction mass slowly under nitrogen atmosphere. The reaction mixture was cooled to 10-15°C and then slowly added isobutyric anhydride (80g) drop wise under nitrogen atmosphere. The reaction mixture was stirred at 45 to 50°C for 18hrs. The reaction mass was then chilled to 0 to 5°C. Quenching of reaction mixture was then done slowly into ice water and then the reaction mass was extracted with methylene dichloride [300 mL x 3 times] and the organic layer was separated. The organic layer was then washed with water and was dried over sodium sulphate bed. The insoluble fraction was filtered off and the content ratio of methylene dichloride was decreased by way of distillation up to 75%. After that added heptane 130 ml and the reaction mass was chilled to 0-5°C. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetra hydro furo [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with heptane, and dried at 50-55°C under vacuum.
Yield: 80g, HPLC Purity > 98%.

Example 7: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-ylmethyl isobutyrate (Formula 3).
The intermediate, 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one (100g) (Formula 4) was dissolved in ethylene dichloride (1150ml) at ambient temperature to get homogeneous solution. 1,8-diazabicyclo[5.4.0]undec-7-ene (35g) and tetra butyl ammonium bromide (3.5) was added in reaction mass slowly under nitrogen atmosphere. The reaction mixture was cooled to 0-5°C and then slowly added isobutyric anhydride (70g) drop wise under nitrogen atmosphere. The reaction mixture was stirred at 25 to 30°C for 16 hrs. The reaction mass was then chilled to 0 to 5°C. Quenching of reaction mixture was then done slowly into ice water and then the reaction mass was extracted with ethylene dichloride [350 mL x 3 times] and the organic layer was separated. The organic layer was then washed with water and was dried over sodium sulphate bed. The insoluble fraction was filtered off and the content ratio of methylene dichloride was decreased by way of distillation up to 80%. After that added heptane 160 ml and the reaction mass was chilled to 0-5°C. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetra hydro furo [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with heptane, and dried at 50-55°C under vacuum.
Yield: 78g, HPLC Purity > 98%.

Example 8: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 3).
The intermediate, 4-amino-1-((3aR,4R,6R,6aR)-6-(hydroxymethyl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)pyrimidin-2(1H)-one (100g) (Formula 4) in isopropyl alcohol (1200ml) was stirred at ambient temperature to get homogeneous solution. 1,8-diazabicyclo[5.4.0]undec-7-ene (45g) and triethyl benzyl ammonium chloride (4g) was added in reaction mass slowly under nitrogen atmosphere. The reaction mixture was cooled to 0-5°C and then slowly added isobutyric anhydride (73g) drop wise under nitrogen atmosphere. The reaction mixture was stirred at 25 to 30°C for 16 hrs. The reaction mass was then chilled to 0 to 5°C. Quenching of reaction mixture was then done slowly into ice water and then the reaction mass was extracted with ethylene dichloride [250 mL x 3 times] and the organic layer was separated. The organic layer was then washed with water and was dried over sodium sulphate bed. The insoluble fraction was filtered off and the content ratio of methylene dichloride was decreased by way of distillation up to 70%. After that added heptane 100 ml and the reaction mass was chilled to 0-5°C. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with heptane, and dried at 50-55°C under vacuum.
Yield: 77g, HPLC Purity > 98%.

Example 9: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2).
The solution mixture of 26 g of hydroxylamine hydrochloride in acetonitrile (200ml), was stirred at ambient temperature for 30 minutes. Chilled the reaction mass to 10-15°C. Adjusted pH of reaction mass to 7 to7.5 by using liquor ammonia solution (30%) and stirred for 30min. Reaction mass was chilled to 0 to 5°C. The intermediate compound ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydro furo[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) (Formula 3) was added slowly. Further reaction mass was maintained at 0 to 5°C for 5 hrs. The water (1200ml) was added to reaction mass at 0 to 5°C, and maintained for 2 hrs. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxylamino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with water, and dried at 50-55°C.
Yield: 85g, HPLC Purity > 98 %.

Example 10: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2).
The solution mixture of 30 g of hydroxylamine hydrochloride in isopropyl alcohol (300ml), was stirred at ambient temperature for 30 minutes. The reaction mass was chilled to 10-15°C. Adjust pH of reaction mass to 7 to7.5 by using liquor ammonia solution (30%) and stir for 45 minutes. The intermediate compound of Formula 3 ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydro furo [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) was added slowly. Further reaction mass was maintained at 10 to 15°C for 8 hrs. The water (800ml) was added to the reaction mass and it was further cooled to 0 to 5°C, and maintained for 1 hr. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with water, and dried at 40-45°C.
Yield: 86g, HPLC Purity > 98 %.

Example 11: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2).
The solution mixture of 25 g of hydroxylamine hydrochloride in methanol (250ml), was stirred at ambient temperature for 30 minutes. The reaction mass was chilled to 10-15°C. Adjusted pH of reaction mass to 7 to 7.5 by using sodium hydroxide solution (20%) and stirred for 30min. Reaction mass was then cooled to 0 to 5°C and intermediate,((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) of Formula 3 was added slowly. Maintained the reaction mass at 0 to 5°C for 6 hrs. The water (1000ml) was added to the reaction mass at 0 to 5°C, and maintained for 2 hrs. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxylamino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with water, and dried at 50-55°C.
Yield: 83g, HPLC Purity > 98 %.

Example 12: Synthesis of the intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (Formula 2)
The solution mixture of 28 g of hydroxylamine hydrochloride in ethanol (400ml), was stirred at ambient temperature for 30 minutes. The reaction mass was chilled to 10-15°C. Adjust pH of reaction mass to 7 to7.5 by using potassium hydroxide solution (25%) and stirred for 30min. Reaction mass was cooled to 0 to 5°C. The intermediate, ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro [3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) of Formula 3 was added slowly. Further reaction mass was stirred at 0 to 5°C for 5 hrs. The water (1200ml) was added to the reaction mass at 0 to 5°C, and maintained for 2 hrs. The precipitated solid product, an intermediate ((3aR,4R,6R,6aR)-6-(4-(hydroxylamino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate was filtered, washed with water, and dried at 50-55°C.
Yield: 84g, HPLC Purity > 98 %.

Example 13: Synthesis of the ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) was added in acetonitrile (400ml) at ambient temperature. Hydrochloric acid (20g) was added into the reaction mixture. The obtained mixture was heated to 55-60°C and maintained for 1.5-2.0 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7 – 7.5 by the addition of aqueous ammonia solution and stirred for 1 hr. The reaction mixture was further heated up to 50-55°C and acetonitrile traces were removed by means of vacuum distillation. Ethyl acetate (650ml) was added into reaction mass which was further removed under vacuum distillation up to 50%. Water (500ml) was added to the reaction mass and aqueous layer was extracted with ethyl acetate (500ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0%. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 4 hrs. The reaction mass was then chilled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl) tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 45g, HPLC Purity > 99%.

Example 14: Synthesis of the ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methylisobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) was added in isopropyl alcohol(800ml) at ambient temperature. Formic acid (35gm) was added into reaction mass and the obtained mixture was heated to about 55-60°C for 4 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7–7.5 by the addition of aqueous ammonia solution and stirred for 45 minutes. The reaction mixture was further heated up to 50-55°C and isopropyl alcohol traces were removed by means of vacuum distillation. Ethyl acetate was (750ml) added into reaction mass, which was further removed under vacuum distillation up to 50%. Water (500ml) was added to reaction mass and aqueous layer was extracted with ethyl acetate (600ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0%. The reaction mass heated to 60-65°C for about 1 hr., then cooled to 20-25°C and stirred 4 hrs. The reaction mass was then cooled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methylisobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 44g, HPLC Purity > 99%.

Example 15: Synthesis of the ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methylisobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl) methyl isobutyrate (100g) was added in methanol (500ml) at ambient temperature. Trifluoro acetic acid (25gm) was added into reaction mass, the obtained mixture was heated to about 55-60°C for 1.5-2.0 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7 – 7.5 by the addition of 10% sodium hydroxide solution and stirred for 1 hr. The reaction mixture was further heated up to 50-55°C and methanol traces were removed by means of vacuum distillation. Ethyl acetate (700ml) was added into reaction mass which was further removed under vacuum distillation up to 50%. Water (500ml) was added to reaction mass and aqueous layer was extracted with ethyl acetate (600ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0 %. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 4 hrs. The reaction mass was then cooled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl) tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 43g, HPLC Purity > 99%.
Example 16: Synthesis of the ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methylisobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-(hydroxyl amino)-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) was added in ethanol (400ml) at ambient temperature. Zirconium tetrachloride (5gm) was added into the reaction mass and the obtained mixture was heated to about 55-60°C for 1.5-2.0 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7–7.5 by the addition of 10% potassium hydroxide solution and stirred for 1 hr. The reaction mixture was further heated up to 50-55°C and ethanol traces were removed by means of vacuum distillation. Ethyl acetate (650ml) was added into reaction mass which was further removed under vacuum distillation up to 50%. Water (500ml) was added to reaction mass and aqueous layer was extracted with ethyl acetate (500ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0%. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 4 hrs. The reaction mass was then cooled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum. Yield: 43g, HPLC Purity > 99%.
Example 17: In-situ Synthesis of ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir)
The solution mixture of 35 g of hydroxylamine hydrochloride in acetonitrile (200ml), was stirred at ambient temperature for 30 minutes. The reaction mass was chilled to 0-5°C. The intermediate compound of Formula 3 ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetra hydro furo[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) obtained by any of the process disclosed in examples 5 to 8 was added slowly. Further reaction mass was maintained at 0 to 5°C for 5 hrs. After reaction completion, the obtained mixture was heated to 55-60°C and maintained for 1.5-2.0 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7 – 7.5 by the addition of aqueous ammonia solution and was stirred for 1 hr. The reaction mixture was further heated to 50-55°C and acetonitrile traces were removed by means of vacuum distillation. Ethyl acetate (650ml) was added into reaction mass which was further distilled under vacuum up to 50%. Water (500ml) was added to the reaction mass and then the aqueous layer was extracted with ethyl acetate (500ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0 %. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 4 hrs. The reaction mass was then chilled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetra hydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 51g, HPLC Purity > 99%.
Example 18: In-situ synthesis of the intermediate ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl) methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The solution mixture of 36 g of hydroxylamine hydrochloride in acetonitrile (350ml), was stirred at ambient temperature for 30 minutes. The reaction mass was chilled to 0-5°C. The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetra hydro furo[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) obtained by any of the process disclosed in examples 5 to 8 was added slowly. Further reaction mass was maintained at 0 to 5°C for 6 hrs. After reaction completion, the obtained mixture was heated to 55-60°C and maintained for 2.0 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7 – 7.5 by the addition of aqueous ammonia solution and stirred for 1 hr. The reaction mixture was further heated up to 50-60°C and acetonitrile traces were removed by means of vacuum distillation. Ethyl acetate (700ml) was added into reaction mass which was further removed under vacuum distillation up to 50%. Water (600ml) was added to the reaction mass and aqueous layer was extracted with ethyl acetate (600ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0 %. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 2 hrs. The reaction mass was then chilled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methy isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 50g, HPLC Purity > 99%.
Example 19: In-situ synthesis of the intermediate ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The solution mixture of 38 g of hydroxylamine hydrochloride in isopropyl alcohol (400ml), was stirred at ambient temperature for 30 minutes. The reaction mass was chilled to 0-5°C. The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyl tetra hydro furo[3,4-d][1,3]dioxol-4-yl)methyl isobutyrate (100g) obtained by any of the process disclosed in examples 5 to 8 was added slowly. Further reaction mass was maintained at 0 to 5°C for 7 hrs. After reaction completion, the obtained mixture was heated to 55-60°C and maintained for 2.5 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7 – 7.5 by the addition of aqueous 10% potassium hydroxide solution and stirred for 1 hr. The reaction mixture was further heated up to 60°C and isopropyl alcohol traces were removed by means of vacuum distillation. Ethyl acetate (700ml) was added into reaction mass which was further removed under vacuum distillation up to 50%. Water (600ml) was added to the reaction mass and aqueous layer was extracted with ethyl acetate (600ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0 %. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 2 hrs. The reaction mass was then chilled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl) tetrahydrofuran-2-yl)methylisobutyrate6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 48g, HPLC Purity > 99%.
Example 20: In- situ synthesis of the intermediate ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl) methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) (Formula 1).
The solution mixture of 40 g of hydroxylamine hydrochloride in isopropyl alcohol (600ml), was stirred at ambient temperature for 30 minutes. Chilled the reaction mass to 0-5°C. The intermediate compound of Formula 3, ((3aR,4R,6R,6aR)-6-(4-amino-2-oxopyrimidin-1(2H)-yl)-2,2-dimethyltetrahydrofuro[3,4-d] [1,3] dioxol-4-yl)methyl isobutyrate (100g) obtained by any of the process disclosed in examples 5 to 8 was added slowly. Further reaction mass was maintained at 0 to 5°C for 7 hrs. After reaction completion, the obtained mixture was heated to 55-60°C and maintained for 3.0 hrs. Reaction mixture was cooled to ambient temperature and was neutralized to obtain pH = 7 – 7.5 by the addition of aqueous 10% sodium hydroxide solution and stirred for 1 hr. The reaction mixture was further heated up to 60°C and isopropyl alcohol traces were removed by means of vacuum distillation. Ethyl acetate (700ml) was added into reaction mass which was further removed under vacuum distillation up to 50%. Water (600ml) was added to the reaction mass and aqueous layer was extracted with ethyl acetate (600ml) and was dried over sodium sulphate. The insoluble fraction was filtered off and the content ratio of ethyl acetate was decreased by way of distillation up to the moisture content NMT 1.0%. The reaction mass was heated to 60-65°C for about 1.0 hr., then cooled to 20-25°C and stirred for 2 hrs. The reaction mass was then chilled to 0-5°C. The precipitated solid product, ((2R,3S,4R,5R)-3,4-dihydroxy-5-(4-(hydroxyamino)-2-oxopyrimidin-1(2H)-yl)tetrahydrofuran-2-yl) methyl isobutyrate 6-fluoro-3-hydroxypyrazine-2-carboxamide (Molnupiravir) was filtered, washed with ethyl acetate, and dried at 40-45°C under vacuum.
Yield: 49g, HPLC Purity > 99%.
As will be readily apparent to those skilled in the art, the present disclosure may easily be produced in other specific forms without departing from its essential characteristics. The present embodiments is, therefore, to be considered as merely illustrative and not restrictive, the scope of the disclosure being indicated by the foregoing description, and all changes which come within therefore intended to be embraced therein.