Enantiomerically Pure Acetals in Organic Synthesis: Resolutions and Diastereoselective Alkylations of Alpha-Hydroxy Esters.

摘要

The diastereomeric tetrahydropyranyl (THP) and tetrahydrofuranyl (THF) ethers of a variety of alpha-hydroxyesters were synthesized and separated by column chromatography. The separability of the diastereomers was found to be a general phenomenon which allowed for wide variations in both the THP/THF ring and the alpha-hydroxyester. The resolved compounds could be deprotonated and alkylated diastereoselectively with a variety of electrophiles. The diastereoselectivity ranged from 1:1 to 12:1 depending on the alpha-hydroxyester, the alkylating agent, and the reaction conditions. In most cases the diastereomeric products of the alkylation were also separated by column chromatography.