Stereocontrol in organic synthesis using silicon-containing compounds. A synthesis of (−)-tetrahydrolipstatin using the alkylation of a β-silyl ester and the hydroboration of an allylsilane
作者:Ian Fleming、Nicholas J. Lawrence
DOI:10.1039/a804275f
日期:——
5S)-5-benzyloxy-3-dimethyl(phenyl)silyl-2-hexylhexadecanoic acid 19. Silyl-to-hydroxy conversion, β-lactone formation, and hydrogenolysis gave the known alcohol (3S,4S)-3-hexyl-4-[(S)-2′-hydroxytridecyl]oxetan-2-one 22, from which tetrahydrolipstatin 1 was prepared by a conventional esterification. Each of the stereochemistry determining steps, 4 → Z-6, 7 → E-8, E-8 → Z-9, Z-6 + Z-10 → Z-12, Z-13a → Z-14a and Z-15 → 16
将双(Z-十三烷基-1-烯基)铜酸盐Z -10共轭添加到(5 S)-1-[(Z)-3'-二甲基(苯基)甲硅烷基丙-2-烯酰基] -5-(三苯甲基氧甲基)吡咯烷酮-2-一Z -6给出3 R-酰亚胺Z -12。随后衍生自该酰亚胺的苄基酯Z -13a的烯酸酯正己基化得到2 R,3 S-酯Z -14a。还原酯基并保护其TBDMS基团的醇,得到烯丙基硅烷(Z)(7 R,8 S)-7-(叔-丁基二甲基甲硅烷氧基甲基)-8-二甲基(苯基)甲硅烷基-9-烯Z -15。氢硼化-氧化得到7 R,8 S,10 S-醇16。保护C-10羟基作为苄基醚,除去甲硅烷基保护基并氧化,得到(2 R,3 S,5 S)-5 -苄氧基-3-二甲基(苯基)甲硅烷基-2-己基十六烷酸19.甲硅烷基到羟基的转化,β-内酯的形成和氢解反应得到已知的醇(3 S,4 S)-3-己基-4- [ (S)-2′-羟基十三烷基]氧杂环丁烷-2-酮