Octalactin A, an antitumor agent containing an eight-membered lactone moiety, has been stereoselectively prepared by means of enantioselective aldol reactions of selected silyl enolates with achiral aldehydes, promoted by a chiral Sn(II) complex. The medium-sized lactone part was effectively constructed by way of a new and rapid mixed-anhydride lactonization using 2-methyl-6-nitrobenzoic anhydride
作者:Paul T. O'Sullivan、Wilm Buhr、Mary Ann M. Fuhry、Justin R. Harrison、John E. Davies、Neil Feeder、David R. Marshall、Jonathan W. Burton、Andrew B. Holmes
DOI:10.1021/ja038353w
日期:2004.2.1
The totalsynthesis of octalactins A and B has been achieved in 15 steps (longest linear sequence) and 10% overall yield from commercially available materials. Key steps include the Paterson-Aldol reaction for the rapid assembly of the carbonate 46, methylenation of 46 and subsequent Claisen rearrangement of the corresponding alkenyl-substituted cyclic ketene acetal to provide the core unsaturated
八内酯 A 和 B 的全合成已通过 15 个步骤(最长的线性序列)和 10% 的市售材料总产率实现。关键步骤包括用于快速组装碳酸酯 46 的 Paterson-Aldol 反应、46 的亚甲基化和随后相应烯基取代的环烯酮缩醛的 Claisen 重排以提供核心不饱和中环内酯 47,以及使用酶-在中环内酯存在下介导的乙酸盐脱保护。
Synthetic efforts toward the synthesis of octalactins
Octalactin B was synthesized from the commercially available methyl-3-butenoate and isobutyraldehyde, using enantioselective allyl- and crotyltitanations to control the stereogenic centers at C3, C4, C7, C8, and C13. Moreover, the two other key-step reactions are a cross-metathesis reaction and a lactonization, using the effective anhydride MNBA, to build up the eight-membered ring lactone. (C) 2008 Elsevier Ltd. All rights reserved.