A total synthesis of didemnins A, B, and C (1-3) which enables these highly cytotoxic cyclopeptides to be prepared in decigram amounts is described. The ß-keto acid unit (hydroxyisovaleryl)propionic acid derivative (Hip, 6) was prepared by acylation of dibenzyl methylmalonate and subsequent cleavage of the benzyl groups by the action of boron trichloride. The free ß-keto acid 6 was activated by the DCC method and allowed to react with the leucine ester 7 to furnish the amide 8. Activation, deprotection, and ring closure of the linear peptide 19 by means of the pentafluorophenyl ester method in a two-phase system gave rise to the didemnin ring skeleton in 75% yield within a few minutes. The respective side chains were then attached to the didemnin ring easily and in high yields by activation of Z-(R)-N-methylleucine as its 3-cyano-2-pyridylthiol ester followed by reaction with Z-lactylproline chloride and Z-lactic acid chloride.
描述了双德米宁 A、B 和 C (1-3) 的全合成,该合成能够以十克的量制备这些高细胞毒性环肽。 β-
酮酸单元(羟基异戊酰)
丙酸衍
生物(Hip,6)是通过
甲基丙二酸二苄酯的酰化以及随后通过
三氯化硼的作用裂解苄基来制备的。通过
DCC 方法激活游离的 β-
酮酸 6,并使其与亮
氨酸酯 7 反应以提供酰胺 8。通过
五氟苯酯方法在两个步骤中对线性肽 19 进行激活、脱保护和闭环。 -相系统在几分钟内以75%的产率产生了二德明宁环骨架。然后,通过将 Z-(R)-N-甲基亮
氨酸活化为其 3-
氰基-2-
吡啶硫醇酯,然后与 Z-乳酰脯
氨酸
氯化物和 Z-
乳酸反应,将各自的侧链轻松且高产率地连接到二聚宁环上酰
氯。