反应详情

56.0 g of 2(S)-amino-3(S)-ethoxycarbonyl-4(R)-pentanolide hydrochloride are dissolved in methylene chloride and the pH is adjusted to 7.5 with sodium bicarbonate solution. The methylene chloride phase is separated off, the aqueous phase is saturated with sodium chloride and extracted repeatedly with methylene chloride, and the organic phases are concentrated by evaporation. 106 ml of 2N sodium hydroxide solution are added dropwise to the residue in 120 ml of ethanol at 0° C. within a period of 6 hours. The solution is then concentrated to half its volume, adjusted to pH 3.9 with 103 ml of 2N hydrochloric acid, and completely concentrated by evaporation. The residue is crystallised from isopropanol/diisopropyl ether, stirred up with methanol and filtered over silica gel. [α]36520 =+14.5° (1% in H2O), m.p. 150°-151° C.

1. customThe methylene chloride phase is separated off
2. extractionextracted repeatedly with methylene chloride
3. concentrationthe organic phases are concentrated by evaporation
4. addition106 ml of 2N sodium hydroxide solution are added dropwise to the residue in 120 ml of ethanol at 0° C. within a period of 6 hours
5. concentrationThe solution is then concentrated to half its volume
6. concentrationcompletely concentrated by evaporation
7. customThe residue is crystallised from isopropanol/diisopropyl ether
8. filtrationfiltered over silica gel
9. custom[α]36520 =+14.5° (1% in H2O), m.p. 150°-151° C.