Asymmetric epoxidation of cis-alkenes with arabinose-derived ketones: enantioselective synthesis of the side chain of Taxol®
作者:Tony K.M. Shing、To Luk、Chi M. Lee
DOI:10.1016/j.tet.2006.01.116
日期:2006.7
The ee values of asymmetric epoxidation of cis-ethyl cinnamate 15 with arabinose-derived ketones as catalyst and Oxone® as the terminal oxidant were found to increase inversely with the size of the catalyst acetal blocking group. Ketone catalyst 2, with the least bulky methoxy acetal group, displayed the best enantioselectivity and afforded ethyl (2R,3R)-3-phenylglycidate 16 in 68% ee. Epoxide 16 was
的不对称环氧化的该ee值顺-乙基肉桂酸酯15与阿拉伯糖衍生的酮作为催化剂和过硫酸氢钾®发现作为终端氧化剂与催化剂缩醛封闭基团的尺寸成反比增加。具有最小体积的甲氧基缩醛基的酮催化剂2显示出最佳的对映选择性,并以68%ee提供了(2 R,3 R)-3-苯基缩水甘油酸乙酯16。环氧化物16被容易地转化为紫杉醇的受保护的侧链®在五个步骤89%的总产率。其他顺式环氧化的对映选择性-烯烃为中等至较差。