A robust method for preparing (3S)-3-alkyl-3-phenyl-1,4-dioxane-2,5-diones was developed using an improved cyclocondensation reaction between (S)-α-alkylmandelic acids and 2-bromocarbonyl halides. Subtle differences in the reaction conditions, including separate additions of triethylamine, significantly increased the yield compared with Schollkopf's original method.
Isomannide and isosorbide as new chiral auxiliaries for the stereoselective synthesis of tertiary α-hydroxy acids
作者:André Loupy、Daphné A Monteux
DOI:10.1016/s0040-4020(02)00024-8
日期:2002.2
isosorbide are selectively protected to provide new chiralauxiliaries suitable for the preparation of enantiopure tertiary α-hydroxyacids. Diastereoselective additions of organozinc reagents on the derived phenylglyoxylates afford the desired α-hydroxyacids with 60–99% ee after saponification. Both absolute configurations of the α-hydroxyacids can be accessed, by adapted choice of either the starting