反应详情

L-Seryl-L-tyrosine methyl ester hydrochloride (taken directly from part a) and 11.7 g. of Nα -benzyloxycarbonyl-L-tryptophan pentachlorophenyl ester [cf. Kovacs et al. J. Org. Chem. 32, 3696 (1967)] are dissolved in 60 ml. of dimethylformamide, cooled to -10° C. with stirring and treated with 28 ml. of triethylamine. The reaction is stirred 11/2 hours at -10° C. and allowed to warm to room temperature with stirring overnight. The mixture is filtered and the filtrate evaporated at 50° C. and reduced pressure. The residue is twice dissolved in methanol and the solvent removed under reduced pressure. The residue is then again taken into 30 ml. of methanol and precipitated by addition of 300 ml. of ether and 100 ml. of petroleum ether. The precipitated oil is obtained by decantation and stirred with 30 ml. of hot ethyl acetate. The product is obtained by cooling and precipitating by addition of ether and petroleum ether. It is further purified by repeating the precipitation from methanol with petroleum ether. The supernatant is decanted and the oil dried at 50° C. and under reduced pressure. The product thus obtained is a tan foam which can be crystallized from methanol, ether and petroleum ether by seeding; m.p. 149°-152° C.; [α]D23 -1.8° (c 1.00, methanol); ultraviolet in methanol, λmax 289.5 E11 92, λmax 280 E11 122.

1. additiontreated with 28 ml
2. stirringThe reaction is stirred 11/2 hours at -10° C.
3. stirringwith stirring overnight
4. filtrationThe mixture is filtered
5. customthe filtrate evaporated at 50° C.
6. dissolutionThe residue is twice dissolved in methanol
7. customthe solvent removed under reduced pressure
8. customof methanol and precipitated by addition of 300 ml
9. customThe precipitated oil is obtained by decantation
10. stirringstirred with 30 ml
11. customThe product is obtained
12. temperatureby cooling
13. customprecipitating by addition of ether and petroleum ether
14. customIt is further purified
15. customthe precipitation from methanol with petroleum ether
16. customThe supernatant is decanted
17. customthe oil dried at 50° C. and under reduced pressure
18. customThe product thus obtained
19. customcan be crystallized from methanol, ether and petroleum ether by seeding