【摘要】 由N端保护的氨基酸或肽与β-羟基-α-氨基酸酯在三苯基膦、三乙胺、四氯化碳的存在下直接缩合,一步就可得到C端含脱氢氨基酸的肽类.在L-苏氨酸甲酯的情况下,全部生成Z型脱氢氨基酸.其可能的反应历程是N端保护的氨基酸或肽与β-羟基-α-氨基酸酯首先缩合形成肽键,然后进一步脱水生成产物.当用同样试剂处理Boc-L-ILe-L-Ser-L-ILe-OMe时,则形成肽类噁唑啉.影响反应方向的主要因素是α—C—H键质子酸性和酰胺N—H键质子酸性的相对强弱.更多还原

【Abstract】 A new synthetic method of dehydropeptides, by direct coupling of N-protected amino acids or N-protected peptides with β-hydroxy -α-amino acid esters in the presence of three equivalents of each of triphenylphosphine, carbon tetrachloride, and triethylamine or ethyl diisopropylamine, was devcloped. Compounds synthesized by this method were Boc-DL-Ile-⊿But-oMe, Boc-DL-Ile-⊿Ala-oMe, Boc-DL-Val⊿Ala-OMe, Boc-L Ile-DL-Val(Thz)-⊿But-oMe, and Boc-L-Ile-DL-Val(Thz)-⊿Ala -oMe. In the case of L-threone methyl ester, only Z-dehydroamino acid residue was observed. A possible mechanism was proposed. It was believed that the Nprotected amino acid or N-protected peptide was coupled first with β-hydroxy -α-amino acid ester, forming a peptide having a β-hydroxyamino acid residue at the C terminal, and then dehydration of the newly formed peptide gave dehydropeptide. The same reagents were used to synthesize peptide oxazolines. The key factor affecting reaction directions was the acidity of the protons at the α-C-H bond and at the N-H bond.更多还原