N-Cbz-Trifluoropyruvaldehyde N,S-ketal: Absolute stereochemistry and addition of Grignard reagents. Highly stereoselective entry to trifluoro analogues of Ephedra alkaloids
作者:Alessandro Volonterio、Pierfrancesco Bravo、Silvia Capelli、Stefano V. Meille、Matteo Zanda
DOI:10.1016/s0040-4039(97)00209-8
日期:1997.3
chiral non racemic N-Cbz-trifluoropyruvaldehyde-N,S-ketal1a (enantiomeric excess up to 74%) is a new trifluoro 3-C building block, which has been reacted with several Grignard reagents, stereoselectively affording the corresponding secondary carbinols 2. The N,S-ketal stereocentre, whose absolute stereochemistry has been determined by X-ray analysis of the α-phenylpropionate 3, is able to provide excellent
手性非外消旋的N -Cbz-三氟丙酮醛-N,S-缩酮1a(对映体过量高达74%)是一种新的三氟3-C结构单元,已与几种格氏试剂反应,立体选择性地提供了相应的二级甲醇2。的Ñ,s ^ -ketal立构,其绝对立体化学已经被α苯丙的X射线分析确定的3,能够提供优异的立体控制。高度立体选择性的对甲苯硫基取代得到N -Cbz-苯基衍生物2d,转化为三氟去氧麻黄碱(S,S)-5和-麻黄碱(S,S)-6 。