Tetrazoles as carboxylic acid surrogates in the suosan sweetener series.

The structure-activity relationship (SAR) in the suosan series of sweeteners has been extended to include additional replacements for the carboxyl group. Tetrazole analogues have been prepared and were found to be sweet. However, both the urea and thiourea tetrazolyl analogues exhibited reduced potency when compared with the carboxyl compounds. Because of the larger size of tetrazole compared with carboxylic acid, chain-shortened tetrazolyl analogues were prepared and found to not be sweet. Some important aspects about the requirements for promoting a sweet taste in vivo can be gleaned from these results. The importance of the degree of delocalization and the orientation of charge density in the anionic group are discussed.