Stereoselective aldol addition of a chiral glycine enolate synthon to heteroaromatic aldehydes

The stereocontrolled addition of (2S)-(+)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine (1) to heterocyclic aldehydes (2) gives mainly a mixture of syn/anti isomers (3) and (4) whose steric configuration was assigned on the basis of spectroscopic data and accepted model for aldol condensation of 1. The possible conversion of adducts to three beta-substituted heteroaromatic serines is demonstrated.