Asymmetric syntheses of panclicins A–E via [2+2] cycloaddition of alkyl(trimethylsilyl)ketenes to a β-silyloxyaldehyde
作者:Philip J. Kocieński、Beatrice Pelotier、Jean-Marc Pons、Heather Prideaux
DOI:10.1039/a800807h
日期:——
Panclicins AâE, pancreatic lipase inhibitors from Streptomyces, were synthesised in a modular fashion starting with three alkyl(trimethylsilyl)ketenes, two amino acids and a single aldehyde component, (3R)-3-(tert-butyldimethylsilyloxy)decanal 11. The lone stereocentre in 11 which governs the stereochemistry in subsequent steps was generated by Noyori asymmetric hydrogenation. The key step, a Lewis acid catalysed [2+2] cycloaddition of alkyl(trimethylsilyl)ketenes 13aâc to 11, gave three 3-trimethylsilyloxetan-2-ones with good 1,3-asymmetric induction. After C- and O-desilylation the amino acid side chains were introduced using a Mitsunobu inversion.
Panclicins A–E,来自链霉菌的胰脂肪酶抑制剂,采用模块化方式合成,起始于三种烷基(三甲基硅基)酮烯、两种氨基酸和一个单一醛组分,(3R)-3-(叔丁基二甲基硅氧基)癸醛11。11中的唯一立体中心通过野依不对称氢化生成,该中心支配后续步骤的立体化学。关键步骤是路易斯酸催化的[2+2]环加成反应,烷基(三甲基硅基)酮烯13a–c与11反应,得到三种具有良好1,3-不对称诱导的3-三甲基硅氧环己-2-酮。经过C-和O-脱硅基化后,利用Mitsunobu翻转引入氨基酸侧链。