Coupling and racemization rate constants of alanine- and glycylalanine-active esters

Abstract

Second-order racemization rate constants (kr ) were determined for the racemization of penta chI oro phenyl (OPcp) and p-nrtrophenyl (ONp) esters of N-carbobenzoxy-L-alanme (Z-L-AJa) and N-carbobenzoxyglycyl-L-alanme (Z-Gly-Ala) in the presence of TEA (triethylamine). The dipeptide-active esters showed the charactenstic 5(4H)-oxazalane IR peak at 5.4.u doing racemization. Second-order coupling rate constants (ko) were determined far the above compounds with valine methyl ester. Significantly higher k/k, ratios were obtained for durinds as compared to monomers and for OPcp than for ONp esters.