II. CHEMISTRY 



323 



2-Amino-4,5-dimethyl-l-ribitylamiiiobenzene (II) might be the next 

 intermcHhate of the l)io8yiithe8is of ribofhiviii since in the presence of al- 

 loxan it is a potent stimulator of Laclobacillus casci.^- This substance is used 

 for the synthesis of riboflavin also by M ijcobaderium tuberculosis. ^^"^ 



As a higher natural intermediate, G , 7-dimethyl-9-D-ribosidoflavin (III) 

 also has been considered, yielding the vitamin by reduction of the N- 

 glycoside linkage.^^ According to Weygand,^^ not only N-D-riboside, but 

 also an N-D-arabinoside could be involved, being transformed by an Am- 

 adori rearrangement to the D-ribose derivative. 



HsC 



H3C 



NH, H3C 



NH2 H3C 



NHCH2(CHOH)3CH20H 



NH, 



II 



I ^ 1 



I OH OH I 



HC— C— C— C— CH2OH 



H H H 



H3C 



H3C 



CO 



NH 



III 



5 -D-Riboflavin-D-glucopyranoside (riboflavinyl glucoside) has been pre- 

 pared by incubation of riboflavin with an enzyme obtained from rat liver^^ 

 Xo function has so far been ascribed to this new derivative of riboflavin. 



Recently light has been thrown on the mechanism of riboflavin biosyn- 

 thesis in Ashbya gossypii by using isotopic compounds.^* C^*-formate intro- 

 duced into the culture medium gave rise to riboflavin tagged in the carbon-2 

 position. The tracer atom from C'^-bicarbonate ended up in the carbon-4 

 position. C'^HsCOOH, CHgC^^OOH, and totally labeled glucose produced 

 riboflavin containing C'^ in both the side chain and o-xylene portions of the 

 molecule. 



The formation of ribose-5-phosphoric acid and the corresponding ketose, 



- 11. P. Sarett, Federation Proc. 4, 101 (1945); J. Biol. Chem. 162, 87 (1946). 

 «" M. I. Smith and E. W. Emmart, J. Immunol. 61, 259 (1949). 

 " L. G. Whitby, Nature 166, 79 (1950); Biochem. J. 50, 433 (1952). 

 »* G. W. E. Plaut, Chem. Eng. News 1632 (April 20, 1953). 



