Switching the Stereochemical Outcome of 6-<i>Endo</i>-<i>Trig</i> Cyclizations; Synthesis of 2,6-<i>Cis</i>-6-Substituted 4-Oxopipecolic Acids
作者:Mark Daly、Alastair A. Cant、Lindsay S. Fowler、Graham L. Simpson、Hans Martin Senn、Andrew Sutherland
DOI:10.1021/jo3022583
日期:2012.11.16
A base-mediated 6-endo-trig cyclization of readily accessible enone-derived α-amino acids has been developed for the direct synthesis of novel 2,6-cis-6-substituted-4-oxo-l-pipecolic acids. A range of aliphatic and aryl side chains were tolerated by this mild procedure to give the target compounds in good overall yields. Molecular modeling of the 6-endo-trig cyclization allowed some insight as to how
甲碱介导的6-内- trig的容易获得烯酮衍生α氨基酸的环化已发展为新颖2,6-直接合成顺式-6-取代的-4-氧代升-pipecolic酸。通过这种温和的方法可以耐受一系列脂族和芳基侧链,从而以良好的总收率得到目标化合物。6-的分子模型内切- trig的环化允许一些见解对如何形成这些化合物中,通过一个平衡过程中生成的烯醇化物中间体,随后互变异构化的不可逆/中和提供用于产物形成的驱动力。立体选择性还原和脱保护所得的2,6-顺式还进行了将6-6-取代的4-氧-1-哌酸转变为相应的4-羟基-1-哌酸。