New high-potency L-aspartyl-3-bicycloalkyl-L-alanine methyl ester sweeteners

A new series of high-intensity sweeteners was prepared in which the phenyl ring of aspartame is replaced by a substituted bicycloalkyl unit. In the case of the L-aspartyl-3-(2-norbornyl)-L-alanine methylesters, methyl substitution of the norbornyl ring increased sweetness potency except in the case of the 1,3,3-trimethylnorbornyl analogue, where a great reduction was found. The two sweetest compounds prepared were the 1,7,7-trimethylnorbornyl and the 7,7-dimethylnorbornyl analogues. For these compounds, the four possible ring stereoisomers were synthesized, and in each case only the 2R-exo and 2R-endo isomers were intensely sweet