抄録
As already shown by us, although n-dihydrothiamine (DHB_1) is very unstable in hydrochloric acid, its solution is easily stabilized by alkalinization, because n-DHB_1 is easily transformed into ps-DHB_1 which is stable in alkaline media. When ps-DHB_1 solution was kept with acetic acid, acetate buffer or phosphate buffer at 35℃, it was found fairly stable to such an extent that 60〜80% of DHB_1 remained unchanged whithin 4 hours, showing much more stability at higher pH values of the solutions. Oxidation of n- or ps-DHB_1 by hydrogen peroxide in acetic acid did not yield thiamine but simultaneously DHB_1 was decomposed into 2-methyl-4-amino-5-aminomethylpyrimidine which was isolated as its sulfate of mp. (decomp.) 265℃. DHB_1 is slowly decomosed in acetate buffer of pH 3.5〜4.5 but at the presence of an excess amount of cyanide or cyanate, formation of thiamine from DHB_1 was favored. Conversion to thiamine from DHB_1 was accelerated by aeration or saturation of oxygen gas and inhibited by expelling air with saturation of hydrogen or nitrogen.
