The cyclization route to the calcitriol A-ring: a formal synthesis of (+)-1α,25-dihydroxyvitamin D3
作者:Chen Chen、David Crich
DOI:10.1016/s0040-4020(01)88018-2
日期:1993.9
An efficient asymmetric synthesis of the A-ring of 1alpha,25-dihydroxyvitamin D3 from alpha-bromoacrolein is described. The key steps of the synthesis are the Evans type syn-selective asymmetric aldol reaction of bromoacrolein with the boron enolate of 3-chloroacetyl-4(S)-isopropyl oxazolidinone and ring closure by Heck type reaction of a vinyl bromide onto an alpha,beta-unsaturated ester in the exo-mode.