Process for producing d,1-5-methyltetrahydrofolic acid and its salts
A method for preparing d,1-5-methyltetrahydrofolic acid and the salts thereof of the formula: STR1 wherein X is hydrogen, an alkaline metal or alkaline earth metal; by reduction of folic acid with sodium borohydride followed by the methylation of the tetrahydrofolic acid thus obtained with aqueous solutions of formaldehyde and sodium borohydride in an inert atmosphere.