β-Hydroxy acids were reacted with hexafluoroacetone and carbodiimides to give carboxy-activated six-membered lactones in good yields. On reaction with amines, the corresponding amides were obtained. We demonstrate the following applications of this protecting/activating strategy: preparation of carboxamides in solution and on solid phase (both normal and reverse mode); recovery and reuse of the excess
Efficient stereoconservative syntheses of 4,4-difluoro-2-hydroxybutyric acids from (S)- and (R)-malic and (S)- and (R)-citramalic acid
作者:Klaus Burger、Torsten Lange、Raul Pires
DOI:10.1016/s0022-1139(99)00296-1
日期:2000.3
A preparative simple stereoconservative synthesis of homochiral 4,4-difluoro-2-hydroxybutyric acid and 4,4-difluoro-2-hydroxy-2-methylbutyric acid using hexafluoroacetone as protecting and activating agent is described.