Asymmetric Total Synthesis of (−)-Callystatin A and (−)-20-epi-Callystatin A Employing Chemical and Biological Methods
作者:Dieter Enders、Jose L. Vicario、Andreas Job、Michael Wolberg、Michael Müller
DOI:10.1002/1521-3765(20020916)8:18<4272::aid-chem4272>3.0.co;2-k
日期:2002.9.16
second intermediate 4 the asymmetric alpha-alkylation of an O-protected derivative of 4-hydroxybutanal was performed exploiting the SAMP/RAMP hydrazone alkylation methodology, and followed by a highly Z-selective Horner-Wadsworth-Emmons reaction under modified conditions. For the synthesis of the polypropionate fragment 5 a diastereoselective syn-aldol reaction was employed between a chiral ethyl ketone
有效的细胞毒性海洋天然产物(-)-Callystatin A及其20-epi类似物的有效不对称全合成已经实现。合成途径涉及三个片段的制备,以在途径的末端彼此偶联。使用3,5-二氧代羧酸酯的生物催化对映选择性还原作为关键步骤获得了第一片段3。对于第二中间体4,利用SAMP / RAMP alkyl烷基化方法进行了O保护的4-羟基丁醛衍生物的不对称α-烷基化反应,然后在修饰条件下进行了高度Z选择性的Horner-Wadsworth-Emmons反应。为了合成聚丙烯酸酯片段5,在手性乙基酮和α-取代的手性醛之间进行了非对映选择性的顺式羟醛反应,两者均通过其相应的RAMP的不对称烷基化再次制备成对映体纯形式。最后,这三个结构单元通过烯丙基三丁基phosph的高度E-选择性Wittig反应偶联,在最终氧化/脱保护序列后得到目标化合物。