Comparison of the Sweetness of Glucose and Fructose With Their Ring‐thio Analogs

ABSTRACT 5‐Thio‐α‐D‐glucopyranose and 6‐thio‐β‐D‐fructopyranose are shown to be significantly sweeter than α‐D‐glucopyranose and β‐D‐fructopyranose, respectively, when tasted in crystalline form. In solution, only the thio analog of glucose is significantly sweeter than its parent sugar. The mutarotational formation of a nonsweet tautomer of thio‐fructose in solution probably accounts for its fall in sweetness intensity. Reasons for the greater sweetness intensity of these thio analogs are proposed. 5‐Thio‐β‐D‐fructofuranose is shown to be essentially tasteless.