Nα-
Nα-
(S)-2-[(S)-2-tert-Butoxycarbonylamino-6-(2-trimethylsilanyl-ethoxycarbonylamino)-hexanoylamino]-6-(2-trimethylsilanyl-ethoxycarbonylamino)-hexanoic acid 4-nitro-phenyl ester
Nα-
(S)-2-tert-Butoxycarbonylamino-6-(2-trimethylsilanyl-ethoxycarbonylamino)-hexanoic acid 3-nitro-phenyl ester