Action of Cyanogen Bromide on Thiamine. III. Synthesis of 2-Methyl-6-(1-methyl-2-thiocyanato-4-hydroxy-1-butenyl)-5,6-dihydropyrimido[4,5-d]pyrimidine (Neocyanothiamine).

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From the measurement of absorption spectrum of thiamine dissolved in sodium ethoxide, it is considered that thiamine is converted into the cyclic thiol-form(III) as a result of intramolecular addition of 4-amino group in the pyrimidine ring and the thiazolium ring, losing hydrochloric acid and opening the thiazole ring. The reaction of 0.1 mole of cyanogen bromide with the cyclic thiol-type thiamine, produced from 0.1 mole of thiamine hydrochloride in ethanol suspension by the action of 0.3 mole of sodium ethoxide, gives 2-methyl-6-(1-methyl-2-thiocyanato-4-hydroxy-1-butenyl)-5,6-dihydropyrimido[4,5-d]pyrimidine (V). This substance is hydrolyzed into N-(1-methyl-2-thiocyanato-4-hydroxy-1-butenyl)-N-[(2-methyl-4-amino-5-pyrimidinyl)methyl]formamide (IV) by dilute acid and converted into thiochrome through thiolcarbamic ester derivative (XIX) on heating with alcohols and also ecomposed into N-[1-(2-thiacyclobutylidene)ethyl]-N-[(2-methyl-4-amino-5-pyrimidinyl)methyl]formamide(VI) and thiamine by the action of sodium hydroxide. On the basis of these experimental results, the mechanism of the formation of thiochrome from thiamine is discussed with that suggested by Sykes, et al. and by Matsukawa, et al.
公益社団法人日本薬学会の論文
1960-04-25