J. Am. Chem. SOC.1981, 103, 7675-7676
7675
Table I. Degree of Racemization during Peptide Bond Formationa ~~
% racemization racemization test
peptide product
conventional coupling O.Sb (azide, 0 "C, 24 h)'"
Anderson test
Z-Gly-Phe-Gly-OEt (9)"
modified Bodanszky test''
Tfa-Ile-Gly-OEt (lo)"
10.lC*d(DCC
Izumiya test' Weygand t e s P
Z-Gly-Ala-Leu-OBzl (11)'' Tfa-Val-Val-OMe (12)''
Oe (azide, 0 "C, 72 h)I3