Decarboxylation of pyruvate by thiamine analogues.

Sources of Compounds Tested-Thiamine hydrochloride (Merck, U.S.P. grade), 0-acetylthiamine hydrochloride and oxythiamine dihydrochloride (California Foundation for Biochemical Research), pyrithiamine hydrobromide and 4-amino-5 aminomethyl-a-methyl pyrimidine dihydrochloride (Nutritional Biochemicals Corporation) were all used without further purification. For determination of pK, values, the 4-amino-5-aminomethyl-2-methyl pyrimidine dihydrochloride was recrystallized from ethanol and ether until it gave the theoretical end point when titrated with base. 5-(2-Hydroxyethyl)I-methyl thiazole was redistilled from pooled commercial products of Merck’ and du Pont. The boiling point was lo%‘, 0.8 mm. Infrared inspection of the redistilled product showed the loss of a strong carbonyl peak which was originally present. The purified product was stored in a desiccator at -20” to hinder oxidation. Salts of 5-(d-Hydroxyethyl)-4-methyl Thiazole-The method of Clarke (6) was employed to prepare the 3-methyl and 3-benzyl (7) and the 3-o-, m-, and p-nitrobenzyl (8) salts. The 3-cr-methylbenzyl salt was prepared by dissolving 0.04 mole each of oc-bromoethyl benzene (Eastman, redistilled 89”, 15 mm.) and 5-(2-hydroxyethyl)-4-methyl thiazole in 4 ml. of thiophene-free anhydrous benzene in a stoppered 18 x 150-mm. test tube. The solution was heated overnight at 55”. The amethylbenzyl salt separates as a light yellow syrup. Attempts to crystallize this compound from a number of solvent systems were all unsuccessful. During crystallization attempts in hot absolute ethanol the salt was partially solvolyzed to the pyrimidylmethyl ethyl ether and 5-(2-hydroxyethyl)-4-methyl thiazole hydrobromide. The absorption spectra in both acid and base and the titration behavior very closely paralleled those of the 3-benzyl salt. These properties plus the method of preparation leave little doubt as to the character of the product. The 3-cyanomethyl salt was prepared in a similar manner from chloroacetonitrile (Eastman white label, redistilled 24O, 27 mm.) and 5-(2-hydroxyethyl)-4-methyl thiazole. The solution was heated at 80’ for 3 days, the benzene supernatant was discarded,