Structure-sweetness relationship of L-aspartyl dipeptide analogs. A receptor site topology

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Abstract
The relationship between structure and the sweet potency of L-aspartyl dipeptide analogs was investigated by physicochemical parameters and regression analysis. The dipeptide analogs reported were divided into the following 4 classes: L-aspartic acid amides, L-aspartylaminoethyl esters, L-aspartylaminopropionates and L-aspartylaminoacetates. The analysis carried out for each class indicated that the electron-withdrawing effect of the substituents directed to the peptide bond and the steric dimensions of the molecules are important in eliciting the sweet taste. The values of coefficients of the electronic .sigma.* terms in the correlations for L-aspartic acid amides, L-aspartylaminoethyl esters and L-aspartylaminopropionates were .apprx. 0.7, indicating a common basic site on the receptor surface. The value for L-aspartylaminoacetates was .apprx. 1.5, and this value suggests, together with the factor of the participation of steric parameters, a closer or geometrically more proper fit to the receptor, explaining the generally higher potency of this class compared to the other 3. The receptor model drawn based on these quantitative analyses appears to be consistent with other classes of sweeteners of apparently unrelated structures.