RIBOFLAVINE 



CH, 



\/\ 



CH3/V/ 

 CH3 



CH3 

 CH3 



CH3 



CH 



CHg. 



\/x 



NO2 



Cl . COOEt 



H . COOEt Ch/^-^^NH . COOEt 



.NH, 



CH. 



D-ribose 



NH.CH2.(CHOH)3.CH20H 



NH. COOEt CH3/ ^ \NH. COOEt 



CHav ^v /NH . CH2 . (CHOH) 3 . CH2OH 



alloxan 



Riboflavine 



CH3/ 



^NHa 



Alloxan is, of course, obtained by the oxidation of uric acid with nitric 

 acid. 



A different synthesis was published later by P. Karrer and H. 

 Meerwein,^ in which 3 : 4-dimethylaniline was reductively condensed 

 with D-ribose, giving 3 : 4-dimethylphenyl-D-ribamine. This was 

 treated with a diazo compound, e.g. diazotised aniline or diazotised 

 _^-nitraniline, and the resulting compound was reduced with sodium 

 dithionite, giving 2-amino-4 : 5-dimethyl-phenyl-D-ribamine, which 

 was coupled with alloxan as before. In the later paper a yield of 

 38 %, based on the D-ribose used, was claimed. 



CH 



NH, 



D-ribose 



CH. 



CH 

 CH3 



diazo- 

 compound 



\/\/ 



NH . CH2 . (CHOH) 3 . CH2OH 



NH . CH2 . (CHOH)3 . CH2OH 



CH; 



CH., 



NH . CH2 . (CHOH) 3 . CH2OH 



CH3/ ^ \NH3 



The method described by Kuhn et al. was covered by a patent ^ 

 assigned to the I.G. and also by a patent ^ assigned by Karrer to 



142 



