Synthesis and sweetness characteristics of L-aspartyl-D-alanine fenchyl esters

Four isomers of the L-aspartyl-D-alanine fenchyl esters were prepared as po tential peptide sweeteners. L-Aspartyl-D-alanine (+)-alpha -fenchyl ester a nd L-aspartyl-D-alanine (-)-beta -fenchyl ester showed sweetness with poten cies 250 and 160 times higher than that of sucrose, respectively. In contra st, L-aspartyl-D-alanine (+)-beta -fenchyl ester and L-:aspartyl-D-alanine (-)-alpha -fenchyl ester had the highest sweetness potencies at 5700 and 11 00 times that of sucrose, respectively. In particular, L-aspartyl-D-alanine (-)-alpha -fenchyl ester had an excellent sweetness quality; but L-,aspart yl-D-alanine (+)-beta -fenchyl ester did not have an excellent quality of s weetness because it displayed an aftertaste caused by the strong sweetness.