Abstract: Salts of riboflavin 5'-phosphate which are obtained by phosphorylation of riboflavin and reaction of the resulting riboflavin 5'-phosphate (5'-FMN), contaminated with unconverted riboflavin and isomeric riboflavin monophosphates and diphosphates, with an alkali metal hydroxide or a nitrogen base are purified by a process in which(a) a roughly 1-15% strength by weight homogeneous, clear, aqueous 5'-FMN salt solution having a pH of from 4 to 7 is prepared from the crude 5'-FMN obtained in the phosphorylation, water and the alkali metal hydroxide or the nitrogen base, preferably sodium hydroxide solution, if necessary with heating at from 30.degree. to 100.degree. C.,(b) the resulting solution is treated with a suitable polymeric adsorber resin and(c) the 5'-FMN salt substantially freed from unconverted riboflavin is isolated from the resulting solution and, if desired, the solution is fed to a subsequent fine purification.

Abstract: Pentoses and hexoses are epimerized by heating sugar dissolved in a solvent in the presence of a molybdenum(VI) compound, by an improved process in which, for the preparation of a sugar having cis OH groups in the 2- or 3-position, of the formula Ia or Ib ##STR1## where R is one of the radicals ##STR2## a homogeneous solution of the corresponding sugar of the formula IIa or IIb ##STR3## is heated to 75.degree.-100.degree. C. in the presence of from 30 to 200 mol %, based on sugar used, of a metal salt of the formula (III)MeX.sub.2 (III)where Me is Mg, Ca, Sr, Ba or Zn and X is Cl or Br, which may or may not contain water of crystallization, and in the presence of from 2 to 20 mol %, based on the sugar used, of a molybdenum(VI) compound.The process is particularly important for the preparation of D-ribose, which is required as an intermediate for vitamin B.sub.2.