SYNTHESIS 



The condensation was best carried out in pyridine. Similarly, 

 5-amino-N-ribityl-ci-4-xylidine and 5 : 5-dichlorobarbituric acid gave 

 an excellent yield of riboflavine. 



Subsequently, Tishler et alP^ found that o-aminoazo compounds 

 reacted with barbituric acid to give riboflavine. 



A similar method had been used previously by Bergel et al.^^ 

 N-D-Ribityl-o-4-xylidine was converted into riboflavine by coupling 

 with diazotised aniline and shaking the azo compound so obtained 

 with excess alloxantin or dialuric acid in an atmosphere of nitrogen 

 and finally oxidising any leuco-riboflavine by shaking in air : 



HO 



NH . CH2 . (CHOH) 3 . CHjOH .C.- O 



, CO CO HO.C CO 



^ rjsf NH NH NH NH 



CO CO^ 

 > Riboflavine 



References to Section 4 



1. R. Kuhn and F. Weygand, Ber., 1935, 68, looi. 



2. R. Kuhn, K. Reinemund, F. Weygand and R. Strobele, ibid., 



1765- 



3. R. C. Hockett and C. S. Hudson, /. Amer. Chem. Soc, 1934, 56, 



1632. 



4. P. Karrer, B. Becker, F. Benz, P. Frei, H. Salomon and K. Schopp, 



Helv. Chim. Acta, 1935, 18, 1435. 



5. P. Karrer and H. Meerwein, ibid., 1935, 18, 1130 ; 1936, 19, 264. 



6. I.G., B.P. 441692. 



7. Hoffmann-la Roche, B.P. 457984. 

 7a. Hoffmann-la Roche, B.P. 628410. 



8. I.G.. B.P. 461245. 



9. R. Kuhn and R. Strobele, Ber., 1937, *^0» 747» 773- 



10. T. Reichstein and M. Steiger, Helv. Chim. Acta, 1936, 19, 189. 



11. C. S. Hudson, U.S. P. 2162721. 



12. F. B. La Forge and C. S. Hudson, /. Biol. Chem., 191 7, 30, 132 ; 



C. S. Hudson, /. Amer. Chem^ Soc, 1939, 61, 343. 



13. F. Weygand, Ber., 1940, 73, 1259. 



14. Miles Laboratories, Inc., B.P. 594949. 



15. Pfizer & Co., Inc., B.P. 545360, 551491, 585212. 



16. Merck & Co., U.S. P. 2424341. 



17. M. Tishler, N. L. Wendler, K. Ladenburg and J. W. Wellman, 



/. Amer. Chem. Soc, 1944, 66, 1328 ; Merck & Co., U.S. P. 

 2420210. 



18. M. Tishler and J. W. Wellman, U.S. P. 2261608. 



19. R. Kuhn and A. H. Cook, Ber., 1937, 70, 761. 



147 



