2,3,3a,4,5,6a-hexahydrofuro[2,3-b]furan-4-yl acetate

Conditions: temp:42.51; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Hexahydrofuro[2,3-b]furan-3-yl acetate (124 g) to the RB flask along with buffer solution (118 g Sodium dihydrogen phosphate dihydrate dissolved in 600 ml water & pH adjusted to 6.5 with saturated NaHCO3 aqueous solution). CAL-B enzyme (19.5 g) was added to the reaction mass and stirred at 40-45° C. Reaction was monitored by Chiral-GC. Reaction was cooled to room temp., dichloromethane (1300 ml) was charged to reaction mass and filtered through hyflow bed. Dichloromethane layer was separated and washed with Sodium chloride solution (10%, 650 ml) and water (3×650 ml). Dichloromethane layer was concentrated under vacuum to get residue of (3R,3aS,6aR)-Hexahydrofuro[2,3-b]furan-3-yl acetate (Yield 53 g). Further, the product was purified by fractional distillation under vacuum at 98-118° C. to get main fraction 39.5 g having purity 97.98%. CAL-B enzyme (19.5 g) was added to the reaction mass Reaction Reaction was cooled to room temp. filtered through hyflow bed Dichloromethane layer was separated washed with Sodium chloride solution (10%, 650 ml) and water (3×650 ml) Dichloromethane layer was concentrated under vacuum

Conditions: temp:5.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Hexahydrofuro[2,3-b]furan-3-ol (25 g) was dissolved in dichloromethane (250 ml) and added triethylamine (23.3 g). N,N-dimethylaminopyridine (0.46 g) was added to the reaction mass. Reaction mass was cooled to 0-10° C. Acetic anhydride (21.5 g) was diluted with dichloromethane (50 ml) & added slowly drop-wise to the reaction mass. Reaction mass was stirred at 0-5° C. till completion. Reaction mass was washed with water (2×100 ml) & 10% Sodium chloride solution (100 ml). Reaction mass was concentrated under vacuum at <40° C. to get residue of Hexahydrofuro[2,3-b]furan-3-yl acetate (yield 29 g). Further, the product was purified by distillation (20 g) under vacuum using fractional distillation at 88-102° C. to get main fraction 17 g having purity 92.6% Reaction mass added slowly Reaction mass Reaction mass was washed with water (2×100 ml) & 10% Sodium chloride solution (100 ml) Reaction mass was concentrated under vacuum at <40° C.

Conditions: temp:41.51; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To the buffer solution (104.3 g of sodium dihydrogen orthophosphate dissolved in 530 mL of water & pH adjusted to 6.0-6.5 with saturated sodium bicarbonate solution (68 g in 680 mL water) solution) hexahydrofuro[2,3-b]furan-3-yl acetate (III, 115 g) and CAL-B (17.25 g) was added at 25-35° C., heated to 38-45° C. and stirred for 24 hours. CAL-B (17.25 g) was added stirred for 16 hours, again CAL-B (11.5 g) was added at 38-45° C. and stirred for 16 hours (pH should maintain 6.0-6.5). The reaction mass was cooled to 20-30° C., methylenedichloride (1150 mL) was added to the mass and stirred for 30 minutes. The reaction mass was filtered through hyflowbed then separated the organic layer and washed with 10% sodium chloride solution (575 mL). Organic layer was distilled completely under vacuum to get title compound II (yield 40.0 g). was added at 25-35° C. CAL-B (17.25 g) was added stirred for 16 hours again CAL-B (11.5 g) was added at 38-45° C. stirred for 16 hours (pH should maintain 6.0-6.5) The reaction mass was cooled to 20-30° C. stirred for 30 minutes The reaction mass was filtered through hyflowbed then separated the organic layer washed with 10% sodium chloride solution (575 mL) Organic layer was distilled completely under vacuum

Conditions: temp:2.51; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Hexahydrofuro[2,3-b]furan-3-ol (IV, 60 g) was dissolved in dichloromethane (300 mL) and cooled to 0-5° C. To the cooled solution triethylamine (58.2 g), N,N-dimethylaminopyridine (1.12 g) was added, acetic anhydride (56.5 g) was added for 30-60 minutes at the same temperature, the mass temperature was raised to 25-35° C. and stirred for 2-4 hours. After completion of reaction the mass was cooled to 10-20° C., water (120 mL) was added, stirred for 30 minutes, separated the organic layer, washed with 10% sodium chloride solution (120 mL) and distilled out dichloromethane to get title compound (yield 72 g). Further, the product was purified by fractional distillation to get pure Hexahydrofuro[2,3-b]furan-3-yl acetate III (yield 54 g). the mass temperature was raised to 25-35° C. After completion of reaction the mass was cooled to 10-20° C. stirred for 30 minutes separated the organic layer washed with 10% sodium chloride solution (120 mL) distilled out dichloromethane