The Synthesis of 4-Hydroxypipecolic Acids by Stereoselective Cycloaddition of Configurationally Stable Nitrones
作者:Franca M. Cordero、Simona Bonollo、Fabrizio Machetti、Alberto Brandi
DOI:10.1002/ejoc.200600104
日期:2006.7
diastereoselective synthesis of trans- and cis-4-hydroxypipecolic acids has been achieved with geometry-controlled nitrone cycloaddition chemistry. The cycloaddition of 3-butenol to enantiopure C-aminocarbonyl and C-alkoxycarbonyl nitrones having a definite (Z) and (E) configuration, respectively, occurs with complete regio- and exo selectivity. The acyclic (Z)-nitrone 12 affords two cycloadducts in a 1:1 ratio
反式和顺式 4-羟基哌可酸的非对映选择性合成已通过几何控制的硝酮环加成化学实现。3-丁烯醇与分别具有明确 (Z) 和 (E) 构型的对映体纯 C-氨基羰基和 C-烷氧基羰基硝酮的环加成反应具有完全的区域选择性和外选择性。无环 (Z)-硝酮 12 以 1:1 的比例提供两种环加合物,它们可以分四步分离并分别转化为 (2R,4R)- 和 (2S,4S)-4-羟基哌啶酸。环状 (E)-硝酮 17 以完全非对映选择性反应,其唯一加合物的制备得到 (2R,4S)-4-羟基哌啶酸甲酯,尽管产率低。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)