FREMGANGSMAADE TIL FREMSTILLING AF RIBOFLAVIN

Riboflavin of the formula I I is prepared by condensation of a 4,5-dimethyl-N-(D)-ribityl-2-phenylazoaniline of the formula II II where X is H, -Cl, -NO2 or -CH3 in the o- or p-position, with barbituric acid of the formula III III in the presence of an acidic condensing agent in an inert organic solvent by an improved process in which the reaction is carried out in an aliphatic diol or triol derivative of the general formula IV (IV) where R1 is H or CH3, R2 is H or CH3- or, when n is 0, is CH3-CO-O-CH2-, R3 is CH3-, C2H5- or CH3-, R4 is CH3-CO-, or is H when R3 is CH3- or C2H5-, and n is 0 or 2, preferably 0, having a boiling point of 80 DEG -180 DEG C., or in a mixture of these as a solvent. In this process, the riboflavin is obtained in particularly pure form and in very good yields.