320 



RIBOFLAVIN 



and the ribonic xylidide, after acetylation, is chlorinated to the imidochlo- 

 ride, which can be reduced smoothly to the amine and then be deacetylated. 



HsC 



H3C 



NHs 



D-ribonolactone 



» IlNHCO(CHOH)3CH20H-^ 

 RNHCO(CHOCOCH3)3CH20COCH3 

 RN=C(CHOCOCH3)3CH20COCH3 



PCU 



H2 



ENH2 



OH- 



Cl 

 RNHCH2(CHOCOCH3) 3CH2OCOCH3 

 RNHCHaCCHOH) 3CH2OH 



In another procedure 3 , 4-dimethylaniHne and tetraacetyl-D-ribonitrile^^ 

 are subjected to catalytic reductive coupling and the resulting acetylated 

 amine is deacetylated. 



Alloxan, which was needed for the earlier synthesis of riboflavin, can be 

 obtained by oxidation of uric acid or barbituric acid. 



The newer methods use barbituric acid or its derivative directly. The 

 condensation of an appropriate o-aminoazo compound with barbituric acid 

 can be carried through in the presence of a weak organic acid, such as acetic 

 acid.'^* 



H3C 



H3C 



R 



I 



N 



N 



\ 



CO 



+ ArNH2 



N 

 Riboflavin 



/ 

 CO 



NH 



L-Lyxoflavin recently was synthesized according to tliis method.'^^ 

 Previously, Bergel et alJ^ used a method to convert N-D-ribityl-o-4- 



'2 K. Ladenburg, M. Tishler, J. W. Wellman, and R. D. Babson, /. Am. Chem. Soc. 



66, 1217 (1944). 

 "M. Tishler and G. H. Carlson, U. S. Pat. 2,350,376 (1944) [C.A. 38, 4963 (1944)]; 



M. Tishler, K. Pfister, 3rd, R. D. Babson, K. Ladenburg, and A. J. Fleming, 



J. Am. Chem. Soc. 69, 1487 (1947). 

 ■'^ D. Heyl, E. C. Chase, F. R. Koniuszy, and K. Folkers, J. Am. Chem. Soc. 73, 



3826 (1951). 

 ^5 F. Bergel, A. Cohen, and J. W. Haworth, /. Chem. Soc. 1945, 165; Hoffman-La 



Roche and Co., British Pats. 550,169 (Dec. 28, 1942) [C.A. 38, 1247 (1944)], 550,836 



(Jan. 27, 1943) [C.A. 38, 1752 (1944)]. 



