The chromium—Reformatsky reaction: Asymmetric synthesis of the aldol fragment of the cytotoxic epothilons from 3-(2-bromoacyl)-2-oxazolidinones
摘要:
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.
The first synthetic advances towards the novel diterpenoid tonantzitlolone 1 are described. The key steps in the synthesis involve a chromium(II) Reformatsky reaction, a diastereoselective C1 extension and an expeditious aldol coupling step of two advanced precursors.