Abstract: Previous investigations have indicated that the thiamine pyrophosphate-dependent enzymatic decarboxylation of pyruvate to acetaldehyde proceeds via the decarboxylation of 2-(l-carboxy-l-hydroxyethyl)-thiamine pyrophosphate (Ia) to 2-(l-hydroxyethyl) thiamine pyrophosphate (IIa). This paper reports the synthesis of an analog of Ia, 2-(l-carboxy-l- hydroxyethyl)-3, 4-dimethylthiazolium chloride (CHDT chloride), and the kinetics of the ...