High-potency dipeptide sweeteners. 2. L-aspartylfuryl-, thienyl-, and imidazolylglycine esters.

Eight L-aspartyl dipeptides derived from heterocyclic glycine esters were prepared and evaluated as sweeteners. The fenchyl esters of L-aspartyl-2-furyl-, 2- and 3-thienyl-, and imidazolylglycine were all potently sweet with the D-2-furylglycine (+)-beta-fenchyl ester being the most potent at 16,500 times the potency of sucrose. The requirement for a planar heterocyclic group directly attached to the glycine carbon atom was demonstrated by the observation that the tetrahydrofuryl and beta-thienylalanine fenchyl esters were not sweet. The heteroaromatic glycine esters join the phenylglycine esters as a novel class of dipeptide sweeteners with very high potency.