The chromium-reformatsky reaction: Asymmetric synthesis of the aldol fragment of the cytotoxic epothilons from 3-(2-bromoacyl)-2-oxazolidinones

In a two step, one pot reaction of 4-benzyl oxazolidinone, 2-bromoacetyl halide, chromium dichloride and a suitable 3-oxo-aldehyde derivative the C1-C6-Me-fragment of epothilons is available in its correct oxidation state and enantiomeric form. Compared to common methods, the chromium-Reformatsky variation preferentially yields the opposite diastereomers and gives improved chemo- and diastereoselection. (C) 1997 Elsevier Science Ltd.