High potency dipeptide sweeteners. 1. L-Aspartyl-D-phenylglycine esters

Twenty esters of L-aspartyl-D-phenylglycine, as well as two substituted analogues, an o-fluoro and a p-hydroxy-phenylglycine ester, were prepared. The L-aspartyl-D-phenylglycine (-)-alpha- and (+)-beta-fenchyl esters had the highest sweetness potency at 1200 and 3700 times that of sucrose, respectively. The high potency of these sweeteners is surprising as the phenyl group occupies a position previously believed to accommodate only much smaller groups.