A highly enantioselective chemoenzymatic synthesis of syn-3-amino-2-hydroxy esters: key intermediates for taxol side chain and phenylnorstatine
作者:J. Augusto R. Rodrigues、Humberto M.S. Milagre、Cíntia D.F. Milagre、Paulo J.S. Moran
DOI:10.1016/j.tetasy.2005.08.015
日期:2005.9
Starting from the bromination of α-ketoesters to obtain 3-bromo-2-oxoalkanoates and bioreduction with Saccharomyces cerevisiae entrapped in calcium alginate pellets with double gel layers, syn-(2R,3S)-β-bromo-α-hydroxy esters were obtained regioselectively in high yields and high ee. These chiral bromohydrins were cyclized to epoxides that were transformed into oxazolidines and finally opened by acidic
从α-酮酸酯的溴化反应开始,获得3-溴-2-氧代链烷酸酯,并用包埋在具有双层凝胶层的藻酸钙沉淀中的酿酒酵母进行生物还原,合成了顺式-(2 R,3 S)-β-溴-α-羟基酯以高产率和高ee区域选择性地获得。这些手性溴醇被环化成环氧化物,然后被转化为恶唑烷,最后通过酸性水解打开,从而以高总收率和高ee产率得到合成-(2 S,3 S)-β-氨基-α-羟基酯。在反应过程中,所有中间体的对映体过量均得以维持。