Abstract
The new oxidized produucts of thiol-type thiamines, 2-(2′-methyl-4′-aminopyrimidyl-5′)-methylformamino-5-hydroxy-Δ2-pentenyl-3-sulfonic acid (thiaminic acid) and its O-benzoyl ester, were obtained by the oxidation of thiamine disulfide or its O-benzoyl ester with hydrogen peroxide. Thiamine alkyl disulfide derivatives, S-acyltype thiamine derivatives and cyanothiamine are also oxidized to thiaminic acid derivatives in similar oxidation reactions. However, no formation was found from thiamine alkylsulfide. Therefore, the thiol-type thiamine derivatives which are converted to thiamine by the reaction with sulfhydryl compounds such as cysteine or protein-SH, produce thiaminic acid derivatives under such oxidation reactions. Thiamine cannot take the thiol form in an acid medium and no thiaminic acid can be formed. Furthermore, by similar oxidation of several aryl thiamine disulfide derivatives or by acylation of thiaminic acid, several thiaminic acid derivatives were obtained. Thiaminic acid is an interesting compound which can be considered to occur in the body as an intermediate of thiamine metabolism and is assumed to be an effective form of so-called “active” thiamine derivatives.
