反应详情

10.0 g of the crude salt from Example 1 were stirred in 15 ml H2O at 80°-90° C. for 30 minutes, cooled below 50° C. and filtered. The solid salt containing 0.03 mole D-histidine tartrate ([α]D +12.17° -C=1.61,H2O) was suspended in 15 ml H2O. With stirring, 0.09 mole (3.6 g) of sodium hydroxide was added and a clear solution was formed. Heat was evolved. Calcium chloride, 0.03 mole (3.33 g) was added and the mixture was stirred at 10°-15° C. for one hour to enable complete precipitation of calcium tartrate. The solid was filtered and washed thoroughly with 3 ml H2O. The filtrate was neutralized with hydrochloric acid 32% (3 ml) to pH=7.5 (isoelectric point) and cooled to 0°-10° C. with stirring for one hour to deposit the free amino acid. The white solid was collected by filtration, washed twice with 3 ml cold methanol: H2O 2:1, then with 2 ml methanol, and dried in vacuo (100° C.) for two hours. D-histidine was obtained in 71.2% yield (3.31 g) with optical purity of 99% ([α]=+39.33). Overall yield from L-histidine=64%. Assay (potentiometric titration, 0.1 NHCl) is 98.99%.

1. temperaturecooled below 50° C.
2. filtrationfiltered
3. customa clear solution was formed
4. temperatureHeat
5. stirringthe mixture was stirred at 10°-15° C. for one hour
6. customprecipitation of calcium tartrate
7. filtrationThe solid was filtered
8. washwashed thoroughly with 3 ml H2O
9. temperaturecooled to 0°-10° C.
10. stirringwith stirring for one hour
11. filtrationThe white solid was collected by filtration
12. washwashed twice with 3 ml cold methanol: H2O 2:1
13. dry with materialwith 2 ml methanol, and dried in vacuo (100° C.) for two hours