The Efficient Preparation of Di- and Tripeptides by Coupling<i>N</i>-(Cbz- or Fmoc-α-aminoacyl)benzotriazoles with Unprotected Amino Acids
作者:Alan R. Katritzky、Parul Angrish、Kazuyuki Suzuki
DOI:10.1055/s-2006-926287
日期:——
N-(Cbz- or Fmoc-α-aminoacyl)benzotriazoles 2 and N-protected peptidoylbenzotriazoles 6 are coupled in aqueous acetonitrile solution with free amino acids or dipeptides to prepare: (i) 22 chirally pure dipeptides 5a-v (in an average yield of 82%) from N-(Cbz- or Fmoc-α-aminoacyl)benzotriazoles 2 and unprotected amino acids, (ii) five chiral tripeptides 7a-e (in an average yield of 75%) from N-protected peptidoylbenzotriazoles 6 and unprotected amino acids, (iii) one chiral tripeptide 7g (62%) from N-(Cbz- or Fmoc-α-aminoacyl)benzotriazole 2a and the free dipeptide 8. In all, N-(Cbz- or Fmoc-α-aminoacyl)benzotriazole derivatives of 17 of the 20 naturally occurring amino acids were used, including those containing the following unprotected side chain functionalities: alcoholic -OH (Ser), indole -NH (Trp), imidazole -NH, phenolic -OH (Tyr), -CONH2 (Gln, Asn), -SH (Cys), -CO2H (Glu, Asp), and -S-S (Cystine). Support for the complete retention of chirality was obtained by parallel experiments involving d-Ala, l-Ala, and dl-Ala for the preparation of di- and tripeptides. This and other evidence for chiral integrity was supported by NMR and HPLC analyses.
在水中用乙腈溶液中,N-(苄氧羰基化或芴甲氧羰基化α-氨酰基)苯并三唑 2 和 N-保护肽基苯并三唑 6分别与游离氨基酸或二肽偶联,制备得到:(i) 22 种手性纯二肽 5a-v (平均产率为 82%),由 N-(苄氧羰基化或芴甲氧羰基化α-氨酰基)苯并三唑 2和未保护的氨基酸制得;(ii) 5 种手性三肽 7a-e (平均产率为 75%),由 N-保护肽苯并三唑 6 和未保护的氨基酸制得;(iii) 1种手性三肽 7g (产率为 62%),由 N-(苄氧羰基化或芴甲氧羰基化α-氨酰基)苯并三唑 2a 和游离二肽 8 制得。全部 20 种天然氨基酸中,含有以下未保护侧链官能团的 17种氨基酸的 N-(苄氧羰基化或芴甲氧羰基化α-氨酰基)苯并三唑衍生物均已使用:醇性-OH(丝氨酸)、吲哚性-NH(色氨酸)、咪唑性-NH,酚性-OH(酪氨酸)、-CONH2(谷氨酰胺、天冬酰胺)、-SH(半胱氨酸)、-CO2H(谷氨酸、天冬氨酸)、-S-S(胱氨酸)。通过使用 D-丙氨酸、L-丙氨酸和 DL-丙氨酸制备二肽和三肽的平行实验,证实了手性的完整保留。并通过 NMR 和 HPLC分析验证了手性完整性的其他证据。