Highly stereoselective total synthesis of pikronolide, the aglycon of the first macrolide antibiotic pikromycin. Crucial role of benzyl-type protecting groups removable by 2,4-dichloro-5,6-dicyanobenzoquinone oxidation.
作者:NORIYUKI NAKAJIMA、TATSUYOSHI TANAKA、TATSUO HAMADA、YUJI OIKAWA、OSAMU YONEMITSU
DOI:10.1248/cpb.35.2228
日期:——
The first total synthesis of pikronolide, the aglycon of pikromycin, isolated as the first macrolide antibiotic, is described. Two segments i (5 : C-1-C-10) and ii (6 : C-11-C-15) were synthesized highly stereoselectively from D-glucose and coupled by Yamaguchi's method to give the ester (17), which was subjected to macrocyclization by means of the intramolecular Wittig-Horner reaction developed by Nicolaou, and the 14-membered cyclic enone (18) was isolated in excellent yield. Removal of protecting groups and Swern oxidation gave pikronolide (2). In this synthesis, 3, 4-dimethoxybenzyl, 4-methoxybenzyl, and benzyl protecting group for hydroxy function played a crucial role.
首次合成了皮克诺利德,皮克霉素的苷元,皮克霉素是第一个被分离的巨环抗生素。两个片段 i (5:C-1-C-10) 和 ii (6:C-11-C-15) 是从 D-葡萄糖高立体选择性合成的,并通过 Yamaguchi 方法结合形成酯(17),该酯随后通过 Nicolaou 开发的分子内 Wittig-Horner 反应进行大环化,最终分离得到了产率极高的 14 元环烯酮 (18)。去保护基团和 Swern 氧化反应得到皮克诺利德 (2)。在这次合成中,3,4-二甲氧苯基、4-甲氧苯基和苯基保护基团在羟基功能上起到了关键作用。