Stereospecific Grignard reactions of cholesteryl 1-alkenesulfinate esters: Application of the Andersen Protocol to the preparation of non-racemic α,β-unsaturated sulfoxides
Synthesis and characterization of homochiral cholesteryl 1-alkenesulfinate esters
摘要:
A number of alpha,beta -unsaturated sulfinyl chlorides 1 has been separately prepared and treated with (-)-cholesterol under various conditions some of which incorporated chiral amines quinine or quinidine. Some (R-S) vinylic sulfinates could be isolated in enantiopure form following one or two recrystallizations of the resulting diastereomeric mixtures of (-)-cholesteryl 1-alkenesulfinates 2. Access to diastereomerically enriched (S-S) vinylic sulfinates (66-75% de) was achieved in three instances. Absolute stereochemical assignments were made with the assistance of the chiral solvating agent (R)-2,2,2-trifluoro-1-(9-anthryl)ethanol. (C) 2001 Elsevier Science Ltd, All rights reserved.