On the Mechanism of Thiamine Action, III. Intermolecular Changes of Thiamine Structure in Alkaline Solution.

The Isolation of a Second Crystalline Antibiotic from Streptomyces erythreus

“…5 The formation of furoin from furfural also has been observed in protein-free, model systems in the presence of various quater-nary thiazole compounds including thiamine6,7 which also catalyzes acetoin formation from pyruvate8 and the diacetylmutase reaction.9 Significantly these reactions proceed only if 2 equivalents of alkali are added per mole of thiamine hydrochloride,8,9 since under these conditions there exist appreciable quantities of thiamine pseudobase. 10 A mechanism for the mode of action of thiamine in these systems has been suggested8,9 which considers that the lone pair of electrons on the tertiary thiazole nitrogen of thiamine pseudobase coordinates with the carbo-cation of pyruvate or diacetyl. The resulting intermediate decarboxylates (or loses a ketone-like group) leaving a complex which acetylates acetaldehyde to form acetoin.…”