Total Synthesis of 4-<i>Epi</i>-A83586C. Epimerisation in a Macrolactamisation Mediated by BOP and DMAP
作者:Karl J. Hale、Jiaqiang Cai、Glyn Williams
DOI:10.1055/s-1998-1606
日期:1998.2
Protected linear hexapeptide 2 undergoes a remarkably facile C(4)-epimerisation when macrolactamisation is attempted with BOP [benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate] and DMAP in CH2Cl2 under conditions of high-dilution; compound 6 is isolated in 51% yield from this reaction. In order to confirm its structure, 6 was independently synthesised from 18 by macrolactamisation with HATU [O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate] and NEM (N-ethylmorpholine); ring-closure now proceeded in 70% yield. After subsequent deprotection by catalytic hydrogenolysis, amine salt 7 was chemoselectively coupled to activated ester 5 to give 4-epi-A83586C (8) after glycal hydration.
在高稀释条件下,用 BOP [苯并三唑-1-基氧基-三(二甲基氨基)磷鎓六氟磷酸盐] 和 DMAP 在 CH2Cl2 中进行大内酰胺化反应,受保护的线性六肽 2 非常容易发生 C(4)-epimerisation 反应;从该反应中分离出化合物 6,收率为 51%。为了确认其结构,6 由 18 通过与 HATU [O-(7-氮杂苯并三唑-1-基)-N,N,N',N'-四甲基脲六氟磷酸盐] 和 NEM(N-乙基吗啉)的大内酰胺化反应独立合成;现在进行闭环反应,收率为 70%。随后通过催化氢解进行脱保护,胺盐 7 与活化酯 5 化学选择性偶联,经过甘氨酸水合反应得到 4-epi-A83586C (8)。