DESC:
FIELD OF THE INVENTION
The present invention relates to a method for the preparation of cholesterol (Compound of Formula I) from bisnoralcohol (Compound of Formula II). More specifically, this disclosure relates to synthesizing intermediates involved in the synthesis of Compound of Formula I in a process efficient method.
BACKGROUND OF THE INVENTION
Cholesterol, having the Formula I is an unsaturated sterol that is essential for human life. Cholesterol plays a vital role, particularly in cell membranes and as a precursor to the biosynthesis of several steroid hormones like oestrogen, testosterone, adrenal hormones, bile acids and vitamin D. Many new cholesterol derivatives bearing a wide range of bioactive scaffolds have been developed in the search for new anticancer, antimicrobial, or antioxidant agents with improved efficacy. The commercialized cholesterol has been extensively used as a raw material in drug delivery, liquid crystal materials, gelators, bio-imaging applications, cosmetics and importantly for producing vitamin D3. Currently, cholesterol is produced from animal origin such as cattle and sheep. There will be potential risks involved with isolation of cholesterol from animal origin, such as swine influenza, sheep anthrax and prion diseases of bovine spongiform encephalopathy (BSE) and scrapie of sheep. For safety concerns, the market demand for producing cholesterol from non-animal-source is highly increasing.
Diosgenin was used as starting material for making cholesterol (CN 100357310). In the first step diosgenin was converted to methyl ether using methyl iodide and sodium hydride as base. In the second step, ketal deprotection was done using 100 equivalent of zinc powder and 30 volumes of concentrated HCl at 100 °C to get diol intermediate. In the third step the diol intermediate was converted into dimesylated compound and in the last step dimesylated compound was deoxygenated using zinc metal and sodium iodide to get cholesterol. The drawbacks of this process are potential risk involved in the usage of sodium hydride in the first step and zinc and concentrated HCl at reflux condition in the second step. In addition the raw material, diosgenin price is on the higher side. Therefore, this process is not viable in producing cholesterol in the production level and commercially unattractive.
WO2021/005618 Al discloses a process for the preparation of cholesterol starting from stigmasterol. Accordingly, the synthetic process for commercial manufacture of cholesterol from stigmasterol, which comprises a) tosylating stigmasterol by treating with p-toluene sulfonyl chloride in a base to obtain stigmasterol tosylate, b) treating the stigmasterol tosylate with methanol in a base to obtain stigmasterol-i-methyl ether, c) treating the stigmasterol-i-methyl ether with ozonized oxygen in a solvent at a temperature range of -50 to -90 °C followed by treatment with reducing agent at a temperature range of -40 °C to 0 0C to obtain (20S)-20-hydroxymethyl-6p-methoxy-3a,5-cyclo-5a-pregnane, d) tosylating the (20S)-20-hydroxymethyl-6p-methoxy-3a,5-cyclo-5a-pregnane with a tosyl chloride in a base to obtain (20S)-6p~10 methoxy-20-(p-toluene sulfonoxy methyl)- 3a,5-cyclo-5a-pregnane, e) subjecting the (20S)-6p-methoxy-20-(p-toluene sulfonoxy methyl)- 3a,5-cyclo-5a-pregnane to Grignard reaction by treatment with isopentyl bromide in an ether solvent in presence of CuBr*Me2S catalyst to obtain i-cholesteryl methyl ether, f) hydrolyzing the i-cholesteryl methyl ether in aq. dioxane with catalytic amounts of p-TSA at a temperature of 70-90 °C to obtain cholesterol. The disadvantages in this method are more number of steps, relatively high in price of the starting material, involves the usage of ozone gas at low temperature, -40 °C to 0 °C which increases process difficulty, providing higher requirements for monitoring reaction the reaction and having poor economy and safety, hence this route is not suitable for industrial production of cholesterol.
Li et al (Steroids 2022, 178, 108967) reported the synthesis of cholesterol using bisnoralcohol as starting material in five steps. First, bisnoralcohol was converted to corresponding aldehyde. Then Wittig reaction using 3,3-dimethylallyl bromide resulted the olefin derivative as mixture of E/Z. The enol ester was obtained by reaction of olefin intermediate with acetyl chloride and acetic anhydride at 80 °C. Sodium borohydride reduction of enol ester followed by reduction of isolated double bond using hydrogen gas/Raney Ni gave the desired cholesterol. The disadvantage in this method is the use of expensive 3,3-dimethylallyl bromide. In addition, the authors have not reported the purity of the obtained cholesterol either by HPLC or by GC.
Subsequently, CN114524856A discloses a process for preparation of cholesterol starting from bisnoralcohol in five steps, which comprises the reaction of bisnoralcohol to corresponding aldehyde, then Wittig reaction using isoamyl bromide to get olefin intermediate. Conversion of this olefin intermediate to enol ester then reduction of this enol ester using sodium borohydride followed by selective reduction of isolated double bond using hydrogen gas/Raney Ni to get cholesterol. The disadvantage of this method is the requirement of higher temperature (> 100 oC) to get phosphonium salt during Wittig reaction. The present inventors also observed that the reaction conditions reported in this patent did not result in the product formation.
Each of the above reported methods for making cholesterol suffer from use of expensive raw materials, hazardous reaction conditions such as ozonolysis and lengthy reaction steps. Hence it can be observed that there is a genuine need for synthesizing cholesterol (Compound of Formula I) in higher yields and of high purity at low cost, which are commercial requirements in an industrial scalable process so that the process can be used directly for the larger scale production. The present inventors have surprisingly developed an efficient process which ameliorates the aforesaid shortcomings of the prior art.
OBJECTS OF THE INVENTION
It is an object of the present invention to overcome the drawbacks of the prior arts.
It is another object of the present invention to provide a process for preparing cholesterol (Compound of Formula I) in an industrial scale by a simple and expedient procedure which results in higher yields and high purity of cholesterol at low cost
It is yet another object of the present invention to provide an efficient process for preparing the intermediates involved in the synthesis of compound of Formula I.
It is yet another object of the present invention to provide a process for preparing cholesterol (Compound of Formula I) in a five-step process.
SUMMARY OF THE INVENTION
According to an aspect of the present invention there is provided an efficient process for preparation of cholesterol (Compound of Formula I).
According to another aspect of the present invention there is provided an efficient process for preparing intermediates involved in synthesis of Compounds of formula I.
DETAILED DESCRIPTION OF THE INVENTION
The following description is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.
Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the scope of the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.
It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, steps or components but does not preclude the presence or addition of one or more other features, steps, components or groups thereof.
The present invention relates to a process for the preparation of cholesterol (Compound of Formula I).
The process described herein results in Compound of Formula I from intermediate Compound of Formula III and Compound of Formula IV in a process efficient manner.
In one embodiment, the present disclosure relates to Compound of Formula I and method for making the same is disclosed from Compound of Formula III and Compound of Formula IV in four steps. In brief, the preparation of Compound of Formula V and Compound of Formula I starting from Compound of Formula II is represented in the below equation (1).

Step (1) involves oxidizing bisnoralcohol of Formula II to obtain the compound of Formula III in presence of solvent and oxidizing agent. In an embodiment, the oxidizing agent at step (i) is selected from mCPBA (meta-chloroperoxybenzoic acid), 30-40% H2O2, peracids, chromic acids, peroxyfluoroactic acid, periodic acid, permanganates under neutral conditions, tertiary butyl hydrogen peroxide, urea-hydrogen peroxide, molecular oxygen, selectflor, TEMPO((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl), NCS (N-Chlorosuccinimide) or combinations thereof.
Accordingly, the present disclosure also relates to a process of preparing Compound of Formula V from intermediates Compound of Formula III and Compound of Formula IV in a process efficient manner.

wherein, R is individually selected from a group comprising alkyl, aryl, heteroaryl, wherein, each of them may be optionally substituted.
In an embodiment, the Alkyl group is selected from methyl, ethyl and t-Butyl isopropyl.
In an embodiment, the Aryl group is selected from phenyl and substituted phenyl derivatives.
In an embodiment, the said Heteroaryl group is selected from pyridine, pyrimidine and quinolone.
A process of obtaining Compound of Formula V from Compounds of Formula III and Compound of Formula IV is represented in the below equation (2)

In one embodiment, the method of making Compound of Formula V is described. Yet in one embodiment, synthesis of Compound of Formula V from Compound of Formula III is described using Compound of Formula IV.
Accordingly, the present disclosure further relates to Compound of Formula V

In an embodiment, the process for preparing Compound of Formula I from Compound of Formula III and Compound of Formula IV include the following steps:
a. Process for obtaining Compound of Formula V

said process comprising reacting Compound of Formula IV

with a base and solvent and working up with solvent to obtain the Compounds of Formula V.
b. Acetylating Compound of Formula V to Compound of Formula VI using a mixture of acid chloride and acid anhydride and a base, then heating the reaction mixture and evaporation of solvents followed by isolating Compound of Formula VI by adding an organic solvent and water, equation (3).

Preferably, Compound of Formula V is dissolved in mixture of acetic anhydride and acetyl chloride and diisopropylethylamine, then heating the reaction mixture to about 60 °C for about 10-20 hours and work-up with an organic solvent and evaporation of solvent to isolate Compound of Formula VI.
c. Reducing Compound of Formula VI to Compound of Formula VII using a reducing agent and a solvent and stirring the reaction mixture and evaporation of solvent followed by isolating Compound of Formula VII as a mixture of beta and alpha isomers in the ratio (9:1), respectively equation (4).

Preferably, the reducing agents used are sodium borohydride, potassium borohydride, lithium borohydride or any hydride source in alcoholic solvents such as ethanol, methanol, isopropanol, n-butanol and non-alcoholic solvents such as THF, or a mixture of solvents. Accordingly, Compound of Formula VI is dissolved in mixture of ethanol and THF and sodium borohydride is added, then stirred the reaction mixture at 0-10 °C for about 4 hours and quenching and work-up with an organic solvent and evaporation of solvent to isolate Compound of Formula VII as a mixture of beta and alpha isomers in the ratio (9:1), respectively. The required beta isomer is isolated by stirring with alcoholic solvent such as methanol and isolated required beta isomer the by filtering the solid.
d. Reducing Compound of Formula VII to Compound of Formula I using a reducing agent and solvent and stirring the reaction mixture and evaporation of solvent followed by isolating Compound of Formula I.

Preferably, the reducing agent used is hydrogen gas/Raney Ni in alcoholic solvents such as isopropanol, ethanol, methanol, n-butanol, or a mixture of solvents, preferably isopropanol. Accordingly, Compound of Formula VII is dissolved in isopropanol and Raney Ni is added, then stirred the reaction mixture at 25-35 °C in the presence of hydrogen gas for about 4 hours and filtering the reaction mixture and evaporation of solvent to isolate Compound of Formula I.

In brief, Compounds of Formula I is obtained from Compounds of Formula III in four steps.

In one embodiment, a series of four steps are used to make cholesterol (Compound of Formula I) from Compound of Formula III and Compound of Formula IV. Yet in one embodiment, the truncated method of synthesis uses the intermediates, Compound of Formula IV (Tetrahedron Letters 2019, 60, 1566–1569), Compound of Formula V, Compound of Formula VI and Compound of Formula VII.




The Compound of Formula III is reacted with Compound of Formula IV and with a base in a suitable solvent at specific temperature and specific time and working-up with an organic solvent to get the Compound of Formula V.
The Compound of Formula V is suspended in an acid anhydride and acid chloride and a base and stirred at specific temperature for a specific time and working-up with an organic solvent to get the Compound of Formula VI.
The Compounds of Formula VI is suspended in a suitable solvent and a reducing agent is added and stirred at specific temperature for a specific time and working-up with an organic solvent to get the Compound of Formula VII as mixture of two isomers (beta and alpha). The desired beta isomer is obtained by stirring with methanol followed by filtration to get Compound of Formula VII.
The Compound of Formula VII is suspended in an alcoholic solvent and hydrogenated using hydrogen gas/Raney Ni in a solvent and stirred at specific temperature for a specific time and filtering the catalyst and solvent to get the Compound of Formula I.
Scheme 1 shows the instant method of synthesizing cholesterol (Compound of Formula I) from Compound of Formula III, apparent from the detailed description that follows.

Scheme 1
In the instant invention, synthesis of cholesterol (Compound of Formula I) using the intermediate, Compound of Formula V, is described herein. More specifically, the synthesis of cholesterol (Compound of Formula I) using the intermediate Compound of Formula V is performed in only four steps to obtain purer compounds in less time and low cost. The instant synthesis of making cholesterol (Compound of Formula I) is also less toxic, safe and cost effective. Although, the present embodiments have been described with respect to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments.
The present disclosure relates to Compound of Formula V



said process comprising reacting Compound of Formula III with Compound of Formula IV using a base in a suitable solvent to obtain the Compounds of Formula V. In an embodiment of the present disclosure, the base is selected from Potassium bis(trimethylsilyl)amide (KHMDS), Lithium bis(trimethylsilyl)amide (LiHMDS), Potassium tert-butoxide (tBuOK), Potassium carbonate (K3CO3), n-Butyllithium (nBuLi), Lithium diisopropylamide (LDA) or any combination thereof, preferably KHMDS. The above process is carried out with an organic solvent, at a specified temperature and a time period ranging from 30 minutes to 72 hours, preferably about 60 minutes to 10 hours. The solvent is selected from Tetrahydrofuran (THF), Cyclopentyl methyl ether (CPME), diethyl ether, dioxane or any combination thereof, preferably THF. The above process further comprises isolation of Compound of Formula V, and wherein, the isolation is carried out by acts selected from a group comprising evaporation, quenching, filtration and extraction or any combination of acts in any order thereof, preferably by extraction.
The present disclosure further relates to a process of obtaining Compound of Formula VI

said process comprising reacting Compounds of Formula V with acid anhydride and acid chloride and a base. In an embodiment of the present disclosure, the acid chloride is selected from acetyl chloride, propionyl chloride, pivaloyl chloride, benzoyl chloride etc., or any combination thereof, preferably acetyl chloride and the acid anhydride is selected from acetic anhydride, propionic anhydride, benzoic anhydride , etc., or any combination thereof, preferably acetic anhydride. The above process is carried out with a base, selected from diisopropylethylamine, trimethylamine, diisopropylamine, etc., or any combination thereof, preferably diisopropylethylamine at a specified temperature and a time period ranging from 30 minutes to 72 hours, preferably about 60 minutes to 16 hours. The above process further comprises isolation of Compound of Formula VI, wherein, the isolation is carried out by acts selected from a group comprising evaporation, quenching, filtration and extraction or any combination of acts in any order thereof, preferably by extraction.
The present disclosure further relates to a process of obtaining Compound of Formula VII

said process comprising reacting Compound of Formula VI with a reducing agent in a suitable solvent to obtain the Compound of Formula VII as mixture of two isomers (beta and alpha). The desired beta isomer is obtained by stirring with methanol and filtration results the beta isomer, Compound of Formula VII. In an embodiment of the present disclosure, the reducing agent is selected from sodium borohydride, potassium borohydride, lithium borohydride, etc., or any combination thereof, preferably sodium borohydride. The above process is carried out with an organic solvent, at a specified temperature and a time period ranging from 30 minutes to 72 hours, preferably about 60 minutes to 10 hours. The solvent is selected from THF, EtOH, CPME, diethyl ether, dioxane or any combination thereof, preferably a mixture of THF and ethanol. The above process further comprises isolation of Compound of Formula VII, and wherein, the isolation is carried out by acts selected from a group comprising evaporation, quenching, filtration and extraction or any combination of acts in any order thereof, preferably by extraction.
The present disclosure further relates to a process of obtaining Compound of Formula I

said process comprising reacting Compound of Formula VII with hydrogen gas/Raney Ni in a suitable solvent to obtain the Compound of Formula I. In an embodiment of the present disclosure, the reducing agent is hydrogen gas/Raney Ni, hydrogen gas/5-10%Pd/C, hydrogen gas/5-10%Rh/C, hydrogen gas/5-10%Pt/C, etc., or any combination thereof, preferably hydrogen gas/Raney Ni. The above process is carried out with an organic solvent, at a specified temperature and a time period ranging from 30 minutes to 36 hours, preferably about 60 minutes to 6 hours. The solvent is selected from isopropanol, THF, EtOH, CPME, diethyl ether, dioxane or any combination thereof, preferably a mixture of isopropanol. The above process further comprises isolation of Compound of Formula I, wherein, the isolation is carried out by acts selected from a group comprising evaporation, quenching, extraction and filtration or any combination of acts in any order thereof, preferably by filtration.
The present disclosure relates to a process of preparing Compound of Formula I
In an embodiment, the present disclosure further relates to a process for preparing cholesterol (Compound of Formula I), said process comprising steps of:
steps a) reacting Compound of Formula III with Compound of Formula IV using base KHMDS in THF solvent at -78°C to obtain Compounds of Formula V
b) reacting Compound of Formula V with acetyl chloride and acetic anhydride and diisopropylethylamine to obtain Compounds of Formula VI
c) reacting Compound of Formula VI with sodium borohydride in mixture of ethanol and THF solvents followed by methanol slurry to obtain Compounds of Formula VII.
d) reacting Compound of Formula VII with hydrogen gas/Raney Ni in isopropanol solvent to obtain Compounds of Formula I.
Method of synthesizing Compound of Formula V:

Compound of Formula V is prepared by the treatment of Compound of Formula III, with Compound of Formula IV in the presence of suitable base and solvent at a temperature of about -78 °C to about 40 °C for a time period ranging from about 30 minutes to 72 hours. Preferably, the reaction is carried out at a temperature of about -78 °C to 30 °C and preferably for a time period of 30 min to 6 h. Then work-up the reaction mixture with a suitable organic solvent.
In an embodiment of the present disclosure, suitable base is selected from KHMDS, LiHMDS, NaHMDS, K2CO3, tBuOK or any combination thereof and the solvent is selected from THF, CPME, diethyl ether, or any combination thereof. Further suitable organic solvent for the work-up is ethyl acetate and the volumes of the solvent is 1-11 normality, preferably 3-5 volumes.
Method of synthesizing Compound of Formula VI:
Compound of Formula VI is prepared by the treatment of Compound of Formula V, with an acid chloride and acid anhydride in the presence of suitable base at a temperature of about -0 °C to about 30 °C for a time period ranging from about 30 minutes to 72 hours. Preferably, the reaction is carried out at a temperature of about 0 °C to 10 °C and preferably for a time period of 30 min to 6 h. Then work-up the reaction mixture with a suitable organic solvent.
In an embodiment of the present disclosure, acid chloride is selected from acetyl chloride, pivaloyl chloride, propionyl chloride, or any combination thereof and the acid anhydride is selected from acetic anhydride and base is selected from diisopropylethylamine, trimethylamine, diisopropylamine, or any combination thereof. Further suitable organic solvent for the work-up is dichloromethane and the volumes of the solvent is 1-11 normality, preferably 3-5 volumes.
Method of synthesizing Compound of Formula VII:
Compound of Formula VII is prepared by the treatment of Compound of Formula VI, with a reducing agent in the presence of suitable solvent at a temperature of about -0 °C to about 100 °C for a time period ranging from about 30 minutes to 72 hours. Preferably, the reaction is carried out at a temperature of about 0 °C to 10 °C and preferably for a time period of 30 min to 6 h. Then work-up the reaction mixture with a suitable organic solvent.
In an embodiment of the present disclosure, the reducing agent is selected from sodium borohydride, potassium borohydride, lithium borohydride, or any combination thereof and the solvent is selected from THF, ethanol, methanol, water, or any combination thereof, preferably mixture of THF and ethanol. Further suitable organic solvent for the work-up is dichloromethane and the volumes of the solvent is 1-11 normality, preferably 3-5 volumes. The desired beta isomer is obtained from a mixture of beta and alpha isomers by slurring with methanol.
Method of synthesizing Compound of Formula I:
Compound of Formula VIII is prepared by the treatment of Compound of Formula VII, with a reducing agent in the presence of suitable solvent at a temperature of about -0 °C to about 100 °C for a time period ranging from about 30 minutes to 72 hours. Preferably, the reaction is carried out at a temperature of about 20 °C to 30 °C and preferably for a time period of 30 min to 6 h.
In an embodiment of the present disclosure, the reducing agent is selected hydrogen gas/Raney Ni, hydrogen gas/5-10%Pd/C, hydrogen gas/5-10%Rh/C, hydrogen gas/5-10%Pt/C or any combination thereof and the solvent is selected from isopropanol, ethanol, methanol, or any combination thereof, preferably isopropanol.
EXAMPLES
The following examples are meant to illustrate the present invention. The examples are presented to exemplify the invention and are not to be considered as limiting the scope of the invention.
Experimental procedure for step-1:

To a solution of compound 1 (40 g, 1.0 Eq.) in DCM (10 V) was added TEMPO (0.01 Eq.) at 0-5 °C and the reaction was stirred for 20 min. Then a solution of sodium bicarbonate (1.4 Eq.) & TBAB (Tetrabutylammonium bromide) (0.09 Eq.) in water (12 V) was added at 0-5 °C. (Note: sodium bicarbonate and TBAB was added to 12 V water). The reaction mass was stirred for 20 min 0-5 °C. Then NCS (1.1 Eq.) was added portion wise in 10 min intervals. The reaction mass was stirred for 3 h. The reaction progress was monitored by TLC (40% EA/Hex). After the completion of the reaction, the reaction mixture was quenched with 15% sodium thiosulphite solution and extracted with DCM (2 x 100 mL) followed by water (100 mL) wash. Organic layer was dried over anhydrous Na2SO4, concentrated under reduced pressure and dried under vacuum at 45 °C to get crude compound 2 as solid. (Crude quantity: 37 g). The obtained compound 2 was given water slurry (2.0 V, with respect to crude weight) for 30 min and filtered the solid. The filtered solid was dried using rotovap until constant weights obtained. The reaction yield was 90%. The obtained compound 2 was confirmed by 1H NMR and LCMS.
Experimental procedure for step-2:

To a solution of compound 3 (1.05 Eq.) in THF (10 V) was cool to -78°C and a solution of 1M KHMDS (1.1 Eq.) added dropwise in 1h. The reaction was stirred for 20 min. Then a solution of compound 2 (28 g, 1.0 Eq.) in THF (10 V) was added slowly at -78 °C. After complete addition of compound 2 the reaction mass was stirred for 4 hours at room temperature. The reaction progress was monitored by TLC (30% EA/Hex). After the completion of the reaction, the reaction mixture was quenched with saturated aq. ammonium chloride solution and extracted with EA (2 x 200 mL). Combined organic layers was dried over anhydrous Na2SO4, concentrated under reduced pressure and dried under vacuum at 45 °C to get crude compound 4 as thick liquid (pale yellow, crude quantity: 30 g). The reaction yield was 90%. The obtained compound 4 was confirmed by 1H NMR.
Experimental procedure for step-3:

To a solution of compound 4 (30 g, 1.0 Eq.) in acetic anhydride (24 Eq.) was added DIPEA (N, N-Diisopropylethylamine) (4 Eq.) and reaction mass cool to 0-5 °C. Then acetyl chloride (25 Eq.) was added dropwise in 30 min intervals. The reaction was stirred for 10 min at 0-5 °C. Then the reaction mass stirred for 16 hrs at 60°C. The reaction progress was monitored by TLC (20% EA/Hex). After the completion of the reaction, the reaction mixture was concentrated under reduced pressure and quenched with water (150 ml) and extracted with DCM (2x 300 mL). Organic layer was dried over anhydrous Na2SO4, concentrated under reduced pressure and dried under vacuum at 45 °C to get crude compound 5 as sticky solid (brown color, crude quantity : 40 g). The obtained compound 5 was given water slurry (2.0 V, with respect to crude weight) for 30 min and filtered (sticky solid). The filtrate was dissolved in DCM and dried using rotovap until constant weights obtained (crude quantity: 35 g). The crude compound was purified by column chromatography (230-400) (product was eluted at 4% EA-H) to get the pure product 5 (solid: 28.5g). The reaction yield was 85%. The obtained compound 5 was confirmed by 1H NMR.
Experimental procedure for step-4:

To a solution of compound 5 (20 g, 1.0 Eq.) in THF (5 V), EtOH (4 V) and water (4V) reaction was stirred for 10 min and cool to 0-5 °C. Then NaBH4 (4 Eq.) was added portion wise in 10 min intervals. The reaction mass was stirred for 4 h. The reaction progress was monitored by TLC (30% EA/Hex). After the completion of the reaction, the reaction mixture was quenched with aq.ammonium chloride (100ml) and concentrated under reduced pressure and extracted with DCM (2 x 200 mL).Then Organic layer washed with brine solution (100 ml) and dried over anhydrous Na2SO4, concentrated under reduced pressure and dried under vacuum at 45 °C to get crude compound 6 as solid. (Crude quantity: 20 g). The crude compound 6 was purified by column chromatography (230-400) (product was eluted at 6-8% EA-H) to get the pure product 6 (solid: 11g). The obtained compound 6 was given MeOH (2.0 V) for 1hr and filtered the solid. The filtered solid was dried using rotovap until constant weights obtained (solid: 10g). The reaction yield was 55%. The obtained compound 6 was confirmed by 1H NMR.
Experimental procedure for step-5:

To a solution of compound 6 (1.0 g, 1.0 Eq.) in IPA (40 V) and added Raney Ni (50 w/w) in autoclave and reaction was stirred at 30 °C for 2.5 hours with 1kg H2 pressure. The reaction progress was monitored by 1H-NMR. After the completion of the reaction, the reaction mixture was filtered through celite bed and concentrated under reduced pressure. The reaction yield was 75%. The obtained compound 8 was confirmed by 1H NMR. (GC purity>98.0%).
Results and Discussion: The cholesterol (Compound of Formula I) is obtained from Compound of Formula III by treatment with Compound of Formula IV to obtain Compound of Formula V. The conversion of Compound of Formula V to Compound of Formula VI is done by treatment of Compound of Formula V with acetyl chloride and acetic anhydride using diisopropylethylamine. Then reduction of Compound of Formula VI using sodium borohydride is performed to get mixture of two compounds (6 & 7), then isolating required compound 6 by methanol slurry followed by filtration. Finally, reduction of the double bond using hydrogen/Raney Ni in isopropyl alcohol is done to obtain cholesterol (Compound of Formula I). Formation of Compound of Formula I is further confirmed by its 1H NMR and LC-MS data.
Comparative example
The present inventors worked on the reaction process reported in CN114524856A and reproduced the same reaction conditions. The reaction was monitored by TLC. It was observed that the TLC showed the starting material intact even after 24 hours; thereby the reaction conditions reported in CN114524856A do not result in the product formation.
Advantages:
The synthesis of cholesterol (Compound of Formula I) involves the use of an intermediate of Compound of Formula III and Compound of Formula IV. By employing these intermediates (Compound of Formula III and Compound of Formula IV), number of steps involved in the synthesis of cholesterol (Compound of Formula I) is significantly reduced when compared to the reported literature methods. The molar yield obtained is 75%with >98% GC purity. The disclosed method of synthesis does not involve expensive reagents such as diosgenin, 3,3-dimethylallyl bromide and higher reactions temperature (>100 °C) as reported in the prior art. The instant synthesis procedure significantly reduces process cycle time, which in turn reduces the cost. In conclusion, the synthesis procedure is industrially scalable, environmentally friendly and safe and very cost effective.
It is to be understood that the present invention is susceptible to modifications, changes and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention.
,CLAIMS:
1. A process for preparing a compound of Formula (V)

Wherein the said process comprises the step of:
Reacting a Compound of Formula III with a Compound of Formula IV to obtain a Compound of Formula V in presence of a base and solvent;


Wherein R is individually selected from alkyl, aryl and heteroaryl groups, wherein, each of the said group may be optionally substituted.

2. The process as claimed in claim 1, wherein the said alkyl group is selected from methyl, ethyl and t-Butyl isopropyl.

3. The process as claimed in claim 1, wherein the said aryl group is selected from phenyl and substituted phenyl derivatives.

4. The process as claimed in claim 1, wherein the said heteroaryl group is selected from pyridine, pyrimidine and quinolone.

5. The process as claimed in claim 1, wherein the said base is selected from Potassium bis(trimethylsilyl)amide (KHMDS), Lithium bis(trimethylsilyl)amide (LiHMDS), Potassium tert-butoxide (tBuOK), Potassium carbonate (K3CO3), n-Butyllithium (nBuLi), Lithium diisopropylamide (LDA) or combinations thereof.

6. The process as claimed in claim 1, wherein the said process is carried out in presence of an organic solvent selected from Tetrahydrofuran (THF), Cyclopentyl methyl ether (CPME), diethyl ether, dioxane or combinations thereof.

7. The process as claimed in claim 1, wherein the said process is carried out at a temperature ranging from -78 °C to 40 °C for a time period ranging from 30 minutes to 72 hours.

8. The process as claimed in claim 7, wherein the temperature is selected from -78 °C to 30 °C for a time period of 30 min to 6 h.

9. A process for preparation of cholesterol of Compound of Formula I

Formula I
Wherein the said process comprises the steps of:
(i) Oxidizing bisnoralcohol of Formula II to obtain the compound of Formula III in presence of solvent and oxidizing agent;


(ii) Reacting the Compound of Formula III from step (i) with a Compound of Formula IV to obtain Compound of Formula V in presence of a base and solvent;


Wherein R is individually selected from alkyl, aryl and heteroaryl groups, wherein, each of the said groups may be optionally substituted;
(iii) Acetylating Compound of Formula V to Compound of Formula VI using a mixture of acid chloride and acid anhydride and a base, heating the said reaction mixture and evaporation of solvents followed by isolating Compound of Formula VI by adding an organic solvent and water;

(iv) Reducing Compound of Formula VI to Compound of Formula VII using a reducing agent and a solvent and stirring the reaction mixture and evaporation of solvent followed by isolating Compound of Formula VII as a mixture of beta and alpha isomers;

(v) Isolating the beta isomer of Formula VII, and reducing it using a reducing agent and solvent to obtain the Compound of Formula I.

10. The process as claimed in claim 9, wherein the oxidizing agent at step (i) is selected from mCPBA (meta-Chloroperoxybenzoic acid), 30-40% H2O2, peracids, chromic acids, peroxyfluoroactic acid, periodic acid, permanganates under neutral conditions, tertiary butyl hydrogen peroxide, urea-hydrogen peroxide, molecular oxygen, selectflor, TEMPO((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl), NCS (N-Chlorosuccinimide) or combinations thereof.

11. The process as claimed in claim 9, wherein the base at step (ii) is selected from Potassium bis(trimethylsilyl)amide (KHMDS), Lithium bis(trimethylsilyl)amide (LiHMDS), Potassium tert-butoxide (tBuOK), Potassium carbonate (K3CO3), n-Butyllithium (nBuLi), Lithium diisopropylamide (LDA) or combinations thereof.

12. The process as claimed in claim 9, wherein the step (ii) is carried out at a temperature ranging from -78 °C to 40 °C for a time period ranging from 30 minutes to 72 hours.

13. The process as claimed in claim 9, wherein the acid chloride at step (iii) is selected from acetyl chloride, propionyl chloride, pivaloyl chloride, benzoyl chloride or combinations thereof; and the acid anhydride is selected from acetic anhydride, propionic anhydride, benzoic anhydride or combination thereof; and the base is selected from diisopropylethylamine, trimethylamine, diisopropylamine or combinations thereof.

14. The process as claimed in claim 9, wherein the reducing agent at step (iv) is selected from sodium borohydride, potassium borohydride, lithium borohydride or combinations thereof.

15. The process as claimed in claim 9, wherein the step (iv) is carried out at a temperature ranging from 0 °C to about 30 °C for a time period ranging from 30 minutes to 72 hours.

16. The process as claimed in claim 9, wherein the reducing agent at step (v) is selected from hydrogen gas/Raney Ni, hydrogen gas/5-10%Pd/C, hydrogen gas/5-10%Rh/C, hydrogen gas/5-10%Pt/C or combinations thereof.

17. The process as claimed in claim 9, wherein the organic solvent at steps (ii), (iv) and (v) is selected from isopropanol, Tetrahydrofuran (THF), ethanol (EtOH), Cyclopentyl methyl ether (CPME), diethyl ether, dioxane or combinations thereof.