Description:FIELD OF THE INVENTION
The present invention is directed to an improved, industrially viable, cost-effective process for the industrial manufacturing of enantiomerically pure (S,S)-2,8-diazabicyclo[4.3.0]nonane of Formula I which is used as an intermediate in the preparation of Moxifloxacin..

BACKGROUND OF THE INVENTION:
(S,S)-2.8-Diazabycyclo[4.3.0] nonane of Formula (I), also named as (4aS,7aS)-2,3,4,4a,5,6,7,7a-octahydro-1H-pyrrolo[3,4-b]pyridine or (4aS, 7aS)-Octahydro-1H-pyrrole[3,4-b]pyridine is well-known in the art as an important intermediate in the manufacturing of Moxifloxacin and many other pharmaceutically active ingredients. The (S,S)-2.8-Diazabycyclo[4.3.0] nonane of Formula (I) is illustrated below.

This intermediate is a most critical to prepare as it has two chiral centres and both having S-configuration. It is also a commercial substance, but the synthesis and optical resolution thereof is currently not satisfactory. Various processes are known in art for the preparation of this intermediate.
EP0350733/ US4990517 / US5059597 /US5416096 / US5607942 are discloses a process for the preparation of racemic 2,8-diazabicyclo[4.3.0]nonane as shown in below scheme.

EP0550903 and US 5,480,879 discloses a process for the preparation of (S,S)-2,8-diazabicyclo[4.3.0]nonane the process of which comprises of separation of the diastereomeric salt of 8-benzyl-2,8-diazabicyclo[4.3.0]nonane of Formula IV using D(-) tartaric acid followed by recrystallization to give enantiomerically pure (S,S)-8-benzyl-2,8-diazabicyclo [4.3.0]nonane of Formula XII followed by debenzylation to form (S,S)-2,8-diazabicyclo[4.3.0]nonane of Formula I as shown in Scheme.

This process comprises extra steps of purification which reduces the product yield and increases cost of the and time. Also it involves use of high vacuum, which is very difficult to achieve at the commercial scale, this adds to the cost of production.

US 6,235,908 discloses using same resolution reagent, L-(+)-tartaric acid and makes improvement on the resolution method for the same intermediate of formula I, wherein expensive DMF is replaced by-butanol or an alcohol/water solvent mixture.

US 5,770,597 disclose a different approach to prepare racemic mixture of cis-(S.S/R,R)-2,8-diazabicyclo[4.3.0]nonane of formula I as showing in Scheme.
The disadvantages of the method is that the first reaction carrying on in slurry formed by DMF and NaH. NaH is a reagent of difficult to be handling and working up. Hydrogen gas is generated during whole reaction period. Furthermore, NaH and DMF mixture system has been reported to cause explosive accidents many times. the route is permitted only for preparing the racemate.

US 6,153,414 discloses enzymatic resolution of the diazabicyclononane racemate by using a transesterification reaction with ethyl acetate in the presence of a lipase from Candida antarctica. However, the reaction proceeds very slowly, requiring 14 days at a temperature of 40° C.

US 7,709,644 B2 discloses enantiomeric enrichment of cis-8-benzyl-7,9-dioxo-2,8-diazabicyclo[4.3.0]nonane, carrying out the enantiomeric enrichment by continuous countercurrent chromatography with simulated moving bed

US 7,692,015 B2 discloses process for preparation of (S,S)-2,8-diazabicyclo[4.3.0]nonane as well as its enantionmer (R,R)-2,8-diazabicyclo[4.3.0]nonane by reacting 2,3-halomethylpyridine with ppropriate substituted sulphonamide to form 6-substituted sulfonyl-6,7-dihydro-5H-pyrrolo[3,4-b]pyridine; reduction of 6-substituted sulfonyl-6,7-dihydro-5H-pyrrolo[3,4-b]pyridine via catalytic hydrogenation on pyridine ring to form 6-substituted sulfonyl-octahydro-pyrrolo[3,4-b]pyridine; resolution of 6-substituted sulfonyl-octahydro-pyrrolo[3,4-b]pyridine via reacting with enantiomerically pure organic acid, e.g. carboxylic acid or sulphonic acid followed by basifying to convert into free amines; leavage of N—S bond of free amines by hydrobromic acid/propionic acid/phenol to give free base of (S,S)-2,8-diazabicyclo[4.3.0]nonane and enantionmer (R,R)-2,8-diazabicyclo[4.3.0]nonane

IN 329/CHE/2008 this patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4.3.0]nonane

IN 322003/ EP 2423211 B1 this patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4.3.0]nonane by comprising 2,3-pyridinedicarboxylic acid with acetic anhydride, (S)-1-phenylethylamine in presence of tetrahydrofuran to produce 6-((S)-1-phenylethyl)-5,7-dihydro-6H-pyrrolo[3,4-b]pyridine-5,7-dione, reduction of 6-((S)-1-phenylethyl)-5,7-dihydro-6H-pyrrolo[3,4-b]pyridine-5,7-dione with Pd(OH)2 to produce (1S,6R)-cis-7,9-dioxo-8-((S)-1-phenylethyl)-2,8-diazabicyclo[4.3.0]nonane, reacting (1S,6R)-cis-7,9-dioxo-8-((S)-1-phenylethyl)-2,8-diazabicyclo[4.3.0]nonane with optically active acid or optically inactive acid to produce (1S,6R)-cis-7,9-dioxo-8-((S)-1-phenylethyl)-2,8-diazabicyclo[4.3.0]nonane salt, de-saltification and reduction of (1S,6R)-cis-7,9-dioxo-8-((S)-1-phenylethyl)-2,8-diazabicyclo[4.3.0]nonane salt to produce (1S,6S)-cis-8-((S)-1-phenylethyl)-2,8-diazabicyclo[4.3.0]nonane and de-protecting (1S,6S)-cis-8-((S)-1-phenylethyl)-2,8-diazabicyclo[4.3.0]nonane to produce (1S,6S)-cis-2,8-diazabicyclo[4.3.0]nonane.

IN 187/CHE/2010 this patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane with catalytic hydrogenation of (S,S)-8-benzyl-2,8-diazabicyclo[4,3,0]nonane in presence of ammonium formate.

US 8,680,276 B2 this patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane by optical resolution with enzymatic hydrolysis of the intermediate dialkyl-1-alkylcarbonylpiperidine-2,3-dicarboxylate racemate of formula (II) isolating the intermediate (2S,3R)-1-alkylcarbonylpiperidine-2,3-dialkyldicarboxylate of formula (III); conversion of the intermediate (III) to (4aR,7aS)-1-alkylcarbonylhexahydrofuro[3,4-b]pyridine-5,7-dione of formula (IV); conversion of the intermediate (IV) to (4aS,7aS)-octahydro-1H-pyrrolo[3,4-b]pyridine or (S,S)-2,8-diazabicyclo[4,3,0]nonane of formula (I)

IN 2823/MUM/2012 This patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane by reduction of diketo compound with reducing agent in the presence of dimethyl sulfate and diglyme.

IN 321410 This patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane by resolution of cis compound 6-benzyl-l,2,3,4,4a,7a-hexahydropyrrolo[3,4-b]pyridine-5,7-dione using D(-)-tartaric acid to form tartrate salt of desired isomer of (4aR,7aS)-6-benzyl-l,2,3,4,4a,7a-hexahydropyrrolo[3,4-b]pyridine-5,7-dione and undesired isomer (4aR,7aS)-6-benzyl-l,2,3,4,4a,7a-hexahydropyrrolo[3,4-b]pyridine-5,7-dione, convert the desired tartrate salt of isomer (4aR,7aS)-6-benzyl-l,2,3,4,4a,7a-hexahydropyrrolo[3,4-b]pyridine-5,7-dione to into free base (4aR,7aS)-6-benzyl-l,2,3,4,4a,7a-hexahydropyrrolo[3,4-b]pyridine-5,7-dione,(4aR,7aS)-6-benzyl-l,2,3.4,4a,7ahexahydropyrrolo[3,4-b]pyridine-5,7-dione is reduced remove oxo groups thereby forming (4aS,7aS)-6-benzyI-l,2,3,4,4a,5,7,7aoctahydropyrrolo[3,4-b]pyridine, (4aS,7aS)-6-benzyl-l,2,3,4,4a,5,7,7a-octahydropynx)lo[3,4-b]pyridine of formula (III) is de-benzylated to form (4aS,7aS)-2,3,4,4a,5,6,7,7aoctahydro-lH-pyrrolo[3,4-b]pyridine or (S,S)-2,8-diazabicyclo[4,3,0]nonane

IN 305924 This patent discloses process for preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane by reduction of diketo compound with reducing agent in the presence of activating agent .

Over to the above prior-art references it is difficult to obtain single configuration product. In all the prior art process using resolution methods to obtain a single configuration product which tends to have the problems of low yield and high cost.

Prior art CN115701431/Organic process research development 26(8), 2022, 2510-2518 are solve the above problem to discloses improved process for preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane by without using resolving agent by stereoselectivity hydrogenation, which shown as below:

However in the above process also having drawbacks as in dia-stereoselective hydrogenation step using Pd/C and pyridine as base and the reaction time is 72 hours and formation of undesired isomer more than 10% as well as pyridine is carcinogenic and hazardous.

OBJECTIVES OF THE INVENTION

The objective of the present invention is to provide a process for the preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane having high yield.

Another objective of the present invention is to provide a process for the preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane which is economical and industrially applicable.

SUMMARY OF THE INVENTION
The present invention relates to a process for the preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I,

which comprising the following steps:
i. hydrogenation of 1,6-bis((R)-1-phenylethyl)-3,4,6,7-tetrahydro1H-pyrrolo[3,4-b]pyridine-2,5-dione compound of Formula II

in presence of Raney nickel and potassium phosphate in a solvent to yield (4aR,7aS)-1,6-bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III

ii. reduction of compound of Formula III in presence of Sodium borohydride, Boron trifluoride etherate in a solvent to yield (4aS,7aS)-1-((R)-1-Phenylethyl)-6-((S)-1-phenylethyl)-octahydro-1H-pyrrolo[3,4-b] pyridine compound of formula IV;

iii. converting the compound of formula IV to cis (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I in presence of palladium carbon in a solvent.
The present invention relates to a process for purification of (4aR,7aS)-1,6-Bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III
treating the crude compound of formula III with diisopropyl ether, Isolating pure compound of formula III.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to process for the preparation of (4aR,7aS)-1,6-Bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III, which comprising of reacting the 1,6-bis((R)-1-phenylethyl)-3,4,6,7-tetrahydro1H-pyrrolo[3,4-b]pyridine-2,5-dione compound of Formula II in the presence of Raney nickel and potassium phosphate in a suitable solvent are selected from the group comprising of methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate. dichloromethane, acetonitrile, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, toluene at a temperature ranging from 25-30oC for about 22-30 hours to provide (4aR,7aS)-1,6-bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III.
The obtained (4aR,7aS)-1,6-bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III can be optionally purified by treating crude compound of formula III with diisopropy ether solvent and cooled to 10-15oC, stirred for 4-5 hours at same temperature to yield pure compound of Formula III.
In another embodiment of the present invention the pure compound of (4aR,7aS)-1,6-bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III is used for preparation of cis (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I.
In another embodiment of the present invention process for the preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I, which comprising reduction of the (4aR,7aS)-1,6-Bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III in presence of sodium borohydride, Boron trifluoride etherate in a suitable solvent are selected from the group comprising of tetrahydrofuran, methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate. dichloromethane, acetonitrile, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, toluene to provide (4aS,7aS)-1-((R)-1-Phenylethyl)-6-((S)-1-phenylethyl)-octahydro-1H-pyrrolo[3,4-b] pyridine compound of formula IV de-protecting the protecting groups in formula IV in presence of palladium carbon in a suitable solvent are selected from the group comprising of tetrahydrofuran, methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate. dichloromethane, acetonitrile, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, toluene to provide compound of formula I
The schematic representation of present invention is shown as below:

In another embodiment of the present invention process for the preparation of 1,6-bis((R)-1-phenylethyl)-3,4,6,7-tetrahydro1H-pyrrolo[3,4-b]pyridine-2,5-dione compound of Formula II which comprising reacting (R)-1-phenylethan-1-amine with ethyl-3-oxobutanone at 5-10oC and reaction mass heated up to 50-55oC and stirred for 4-5 hours at same temperature and cooled to 25-30oC, cyclohexane added to above reaction mass and stirred for 10-15 minutes at 25-30oC, separate the organic layer and dimethylformamide was added at 25-30oC, cooled to 0-5oC. Acrolyl chloride was added to reaction mass at 0-5oC and heated 25-30oC and stirred for 2-3 hours, cooled to 0-5oC, quench with 10% Na2CO3 solution, separate the layer and extract with cyclohexane. Combined organic layer and distil under reduced pressure below 45oC. Ethyl acetate was added to above residue and cooled to 0-5oC. 1,3-dibromo-5,5-dimethylhydantion was added to above reaction mass and at 0-5oC for 1 hour, reaction mass heated 60-65oC and stirred for 3-4 hours and cooled to 0-5oC, added 10% Na2CO3 solution drop wise over period of 30-45 minutes and stirred for 30-45 minutes. Separate the layers and aqueous layer extract with ethyl acetate, combined the organic layers distil under reduced pressure. Isopropyl alcohol was added to above residue and heat to 60-65oC and stirred for 30-45 minutes, cooled to 15-20oC and stirred for 4-5 hours. Filter the solid and wash with isopropyl alcohol to get Ethyl-R-2-(2-bromomethyl-6-oxo-1-(1-phenyl-1,4,5,6-tetrahydropyridine-3-carboxylate. Ethyl-R-2-(2-bromomethyl-6-oxo-1-(1-phenyl-1,4,5,6-tetrahydropyridine-3-carboxylate was dissolved in ethyl acetate, water and sodium carbonate R-1-phenyl-1-amine was added to above reaction mass for 30-45 minutes at 25-30oC, heated 70-75oC and stirred for 10-12 hours, cooled to 25-30oC, separate the layers and the organic layer distil under vacuum below 50oC. Diisopropyl ether was added to above solid at 25-30oC, cooled the reaction mass 0-5oc and stirred for 4-5 hours, filter the solid and wash with diisopropyl ether to get 1-(R)-1-phenylethyl)-6-(S)-1-phenylethyl)-3,4,6,7-tetrahydro-1H-pyrrolo[3,4-b]pyridine-2,5-dione compound of formula II.
In another embodiment of the present invention (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I that is obtained as described above can be used as an intermediate in the preparation of Moxifloxacin.
.
In another aspect the present invention is advantageous over prior art as follows:
• Time required is only 25-30 hours for the reduction of Formula II to Formula III
• Avoiding the high time
• Avoiding the using of carcinogenic pyridine

The use of Raney Nickel in presence of potassium phosphate in reduction step makes the process more cost-effective and amenable for large scale preparation, which avoids use of costly reagents and carcinogenic pyridine w.r.t known prior art process. Further the advantages of the present invention w.r.t. prior art process is as follows:
Prior-Art Present Invention
% Yield of Compound of formula III 85% 96%
HPLC purity 99% 99.7%
Catalyst Pd/C Raney nickel
Base Pyridine Pyridine Potassium phosphate
Time 72 hours 25-30 hours

In the following section embodiments are described by way of examples to illustrate the process of invention. However, these do not limit the scope of the present invention. Variants of these examples would be evident to persons ordinarily skilled in the art.

Reference example

Process for preparation of (4aR,7aS)-1,6-Bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione.
1.80 kg (4.99 mol, 1.0 equiv) of 1,6-bis((R)-1-phenylethyl)-3,4,6,7-tetrahydro1H-pyrrolo[3,4-b]pyridine-2,5-dione 11f was added to 9 L of ethanol in a hydrogenation reactor, followed by 0.24 kg (3.00 mol, 0.6 equiv) of pyridine and 0.18 kg of 5% palladium on carbon. Stirring was continued for 72 h under 2 MPa hydrogen pressure. After reaction completion the catalyst was removed and washed with 1.8 L of ethanol. The clear filtrate was concentrated under reduced pressure at a temperature below 50°C to obtain an off-white crude product. The solid was redissolved in 2.5 L of isopropyl acetate at 80°C and stirred for 30 min; then 5.4 L of n-heptane was added, and the suspension was cooled to 0°C and stirred for another 4 h. The product was collected by centrifugation and washed with nheptane (1 L). It was dried to constant weight to yield 1.54 kg of (4aR,7aS)-1,6-bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione
Yield: 85%.
HPLC purity: 99%

Examples:

Example 1: Process for preparation of Ethyl-R-2-(2-bromomethyl-6-oxo-1-(1-phenyl-1,4,5,6-tetrahydropyridine-3-carboxylate:

Ethyl acetoacetate (225.4g) was take in reaction flask at 25-30oC and the reaction mass was cooled to 5-10oC, (R)-1-phenylethan-1-amine was added to at same temperature and reaction mass was heated up to 50-55oC and stirred for 4-5 hours at same temperature and cooled to 25-30oC. Cyclohexane and 10% sodium chloride was added to 10-15 minutes, separate the layers and taken the organic layer. Dimethyl formamide was added at 25-30oC and cooled to 0-5oC, acrolyl chloride was added dropwise at same temperature and heated up to 25-30oC and stirred for 2-3 h. Cooled to 0-5oC and quench with Na2CO3 solution, separated the layers taken the organic layer and washed with sodium chloride solution and distilled under reduced pressure. Ethyl acetate was added to above residue and at 25-30oC and the reaction mass was cooled to 0-5oC. 1,3-dibromo-5,5-dimethylhydantoin was added to at 0-5oC for 1 hour and reaction mass heated up to 60-65oC and stirred for 3-4 hours and cooled to 0-5oC . Na2CO3 was added drop wise to above reaction mass for 30-45 minutes and heated up to 25-30oC and stirred for 30-45 minutes, separated the layers and combined organic layers and washed with Na2S2O3, water and sodium chloride solution and distilled under reduce pressure. Isopropyl alcohol was added to above obtained residue and heated up to 60-65oC and stirred for 30-45 minutes. Cooled to 15-20oC and stirred for 4-5 hours. Filter the solid and washed with isopropyl alcohol and suck dry 30 minutes. Dried the solid at 50oC for 6-8 hours.
Yield: 302 g

Example 2: Process for preparation of 1-(R)-1-phenylethyl)-6-(S)-1-phenylethyl)-3,4,6,7-tetrahydro-1H-pyrrolo[3,4-b]pyridine-2,5-dione.
Ethyl-R-2-(2-bromomethyl-6-oxo-1-(1-phenyl-1, 4, 5, 6-tetrahydropyridine-3-carboxylate, ethyl acetate, water and sodium carbonate were charged at 25-30oC. Slowly add (R)-1-phenylethan-1-amine to the above reaction mass 30-45 minutes and heated up to 70-75oC and stirred for 10-12 hours. Cooled to 25-30oC and separated the layers, taken the organic layer washed with dilute hydrochloric acid and water, distilled under vacuum below 50oC. Diisopropyl ether was added to above solid at 25-30oC, cooled the reaction mass at 0-5oC and stirred for 4-5 hours. Filter the solid and washed with diisopropyl ether. Dried the solid for 4-5 hours at 45-50oC.
Yield: 177g
% Yield: 90%

Example 3: Process for preparation of (4aR, 7aS)-1(R)-1-phenylethyl)-6-(S)-1-phenylethyl)hexahydro-1H-pyrrolo-[3,4-b]pyridine-2,5-dione.

1-(R)-1-phenylethyl)-6-(S)-1-phenylethyl)-3,4,6,7-tetrahydro-1H-pyrrolo[3,4-b]pyridine-2,5-dione, methanol, potassium phosphate and Raney Nickel were taken in hydrogenation flask at 25-30oC and stirred for 25-30 hours. Filtered the reaction mass through hiflo bed and washed with methanol. Filtrate distilled under vacuum below 50oC. Diisopropyl ether was added to above crud product, cooled to 10-15oC and stirred for 4-5 hours. Filtered the solid and washed with diisopropyl ether and dried the solid at 45-50oC.
Yield: 95 g
%Yield: 96%
HPLC purity: 99.7%

Example 4: Process for preparation of (4aS, 7aS)-1(R)-1-phenylethyl)-6-(S)-1-phenylethyl)octahydro-1H-pyrrolo-[3,4-b]pyridine

Charged (4aR, 7aS)-1(R)-1-phenylethyl)-6-(S)-1-phenylethyl)hexahydro-1H-pyrrolo-[3,4-b]pyridine-2,5-dione and Tetrahydrofuran in reaction flask at 25-30oC and stirred for 10 minutes. Sodium borohydrate was added lot wise to above reaction mixture for 30-45 minutes and stirred for 10-15 minutes at 25-30oC. Cooled to 0-5oC and 50% BF3.etharaste was added to drop wise, stirred for 20-30 minutes. The temperature of reaction mass was raised up to 25-30oC and maintained for 5-6 hours. Cooled to 0-5oC and quench with dil. Hydrochloric acid, raised reaction mass temperature 25-30oC and stirred for 14-16 hours at same temperature and distilled the solvent below 50oC. Cooled to 25-30oC, water and ethyl acetate were added, then PH adjusted to 9-10 with sodium hydroxide solution, separate the layers and combined the organic layers washed with sodium chloride solution and distilled under vacuum at below 50oC to provide syrupy product.
Yield: 90g
%Yield: 97.6%

Example 4: (S,S)-2,8-diazabicyclo[4,3,0]nonane.
Charged Methanol (900ml), (4aS, 7aS)-1(R)-1-phenylethyl)-6-(S)-1-phenylethyl)octahydro-1H-pyrrolo-[3,4-b]pyridine (90g) and Pd/C (10.8g) in reduction flask at 25-30oC and heated to reaction mass 60-65oC and maintained for 22-24 hours. Cooled the reaction mass 25-30oC. Filtered the reaction mass through hiflo bed and washed with methanol and completely distilled the filtrate. Water and cyclohexane were added to above filtrate and separate the layers. Take aqueous layer and distilled under vacuum at below 70oC and co distiled with methanol. Methanol and heptane were added to above residue and stirred for 15-20 minutes and separate the methanol and heptane layers, methanol layer wash with heptane and distilled under vacuum at below 50oC to afford the (S,S)-2,8-diazabicyclo[4,3,0]nonane as syrup.
Yield: 28 g (82%)
, Claims:We claim:

1. A process for the preparation of (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I,
which comprise:
i. hydrogenation of 1,6-bis((R)-1-phenylethyl)-3,4,6,7-tetrahydro1H-pyrrolo[3,4-b]pyridine-2,5-dione compound of Formula II,

in presence of Raney nickel and potassium phosphate in a solvent to yield (4aR,7aS)-1,6-bis((R)-1-phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of Formula III,

ii. reduction of compound of Formula III in presence of sodium borohydride, Boron trifluoride etherate in a solvent to yield (4aS,7aS)-1-((R)-1-Phenylethyl)-6-((S)-1-phenylethyl)-octahydro-1H-pyrrolo[3,4-b] pyridine compound of formula IV

iii. converting the compound of formula IV to cis (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I in presence of palladium carbon in a solvent.

2. The process according to claim 1, wherein the solvent is selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate. dichloromethane, acetonitrile, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, toluene, tetrahydrofuran, ethyl acetate and /or mixture of solvents.
3. The process according to claim 1, wherein the reaction is carried out at a temperature from 25-30oC.
4. The process according to claim 1, (S,S)-2,8-diazabicyclo[4,3,0]nonane compound of formula I, is used as an intermediate in the preparation of Moxifloxacin.

5. A process for purification of (4aR,7aS)-1,6-Bis((R)-1- phenylethyl)hexahydro-1Hpyrrolo[3,4-b]pyridine-2,5-dione compound of formula III by treating with diisopropyl ether and isolating pure compound of Formula III.