C(=O)([O-])O.[NH4+].O.[C:7]([NH:10][CH:11]([CH2:17][C:18]1[CH:22]=[CH:21][S:20][CH:19]=1)[C:12]([O:14][CH2:15][CH3:16])=[O:13])(=[O:9])[CH3:8]>C(#N)C>[C:7]([NH:10][C@H:11]([CH2:17][C:18]1[CH:22]=[CH:21][S:20][CH:19]=1)[C:12]([O:14][CH2:15][CH3:16])=[O:13])(=[O:9])[CH3:8]3.95 g of ammonium hydrogen carbonate and 35 cm3 of deionized water are added to a stirred solution, under an inert atmosphere, of 2.41 g of ethyl 2-(acetylamino)-3-(3-thienyl)propanoate in 17 cm3 of acetonitrile. 0.017 g of type-II α-chymotrypsin is added and the pH of the reaction medium is then in the region of 8. This mixture is stirred for 1 hour at room temperature and, after checking that the pH is still at 8, a further 0.017 g of type-II α-chymotrypsin is added. After stirring for 1 hour, with the pH remaining constant, a further 0.017 g of type-II α-chymotrypsin is introduced and stirring of the reaction mixture is continued for 19 hours at room temperature. The acetonitrile is evaporated off under reduced pressure (2 kPa) at a temperature in the region of 33° C. and 25 cm3 of ethyl acetate are then added to the residual aqueous phase. The emulsion obtained is filtered through Celite and the aqueous phase is then extracted with twice 25 cm3 of ethyl acetate. The organic phases are combined, washed with twice 15 cm3 of sodium carbonate solution and then evaporated under reduced pressure (2 kPa) at a temperature in the region of 40° C. The solid residue is then dried in an oven under vacuum (10 Pa) at room temperature. 1.1 g of ethyl (2R)-2-(acetylamino)-3-(3-thienyl)propanoate are obtained in the form of a beige-colored solid melting at about 75° C.
Loading…
