α-Amino Acids andN-Protected α-Amino Aldehydes by Stereoselective Additions of a Chiral Vinyllithium Reagent to Sulfonylimines
作者:Manfred Braun、Kersten Opdenbusch
DOI:10.1002/jlac.199719970121
日期:1997.1
proven by conversion into the oxazolidinones 16a–d whose optical purity is determined to exceed 92% e.e. by 1H-NMR measurements in the presence of chiral shift reagents. The sulfonylimine 21a and a series of para-substituted derivatives 21b–h are also allowed to react with the vinyllithium reagent 1b to give mixtures of diastereomers 22/23. The logarithms of the diastereomeric ratios 22:23 correlate with
手性试剂乙烯基锂(小号) - 1B,从容易二溴烯烃生成(小号) - 1A由溴/锂交换,立体选择性地添加到mesitylsulfonylimines 2A-F ,使得非对映体3在⩾98%获得德柱色谱法之后。将溴代烯烃3a-d在甲醇中进行臭氧分解,得到α-间苯二甲磺酰基氨基酯(S)-8a -d,可以将其水解以提供> 95%ee的N保护的α-氨基酸。另一方面,α-间苯二甲磺酰基氨基醛12a–d当溴代烯烃3a,d–f首先脱溴(11a–d),然后进行臭氧化处理时,可以使用这些化合物。为了避免再聚合,不纯化醛12a-d,而是进行Mukaiyamatype羟醛加成,从而在螯合物控制的反应中将羟基酯15a-d形成为单一非对映异构体。酯15a-d的相对构型可通过转化为恶唑烷酮16a -d来证明,恶唑烷酮16a-d的光学纯度通过1 H-NMR测定在手性位移试剂存在下超过92%ee。磺酰亚胺碱21a和一系列对位