555 



Pteridines and Flavines 



(in leucopterin from butterflies) are furnished quite di- 

 rectly by glucose. Over 50 percent of the activity of 

 D-glucose-1-C" was found in these two positions, and 

 acetate was excluded as a direct precursor of this part of 

 the molecule.-^' 



A sugar origin for this part of the pteridine ring is sug- 

 gested, too, by the natural occurrence of such substances 

 as erythropterin and biopterin, although, in these cases, 



OH OH 

 OH _ OH 



N ^ 



H.N 



OH 



C=C— CH> 



CH— CH— CH3 



N 



^^ 



N^^N 



HoN 



OH OH OH 



Erythropterin Biopterin 



pentoses would be expected. Both erythropterin and 

 biopterin, incidentally, occur as glycosides. If a precursor 

 such as this were assumed, it would relate these sub- 

 stances closely with the riboflavin structure. There is 

 experimental support for the assumption of the pyrimi- 

 dine shown as a riboflavin precursor.^" 



NH. 



CH2 



1 



CH— CH— CH— CH2 



1111 

 OH OH OH OH 



O 



CHj 



CH3 



CH2 



I 

 CH— CH— CH— CH2 



I I I I 



OH OH OH OH 



Assumed pteridine 

 precursor 



Riboflavin 



Many pteridine derivatives related to the pteridine 



-' F. Weygand, H.-J. Schliep, H. Simon and G. Dahms, ibid. 71 522 

 (1959). 



-^ Toyokazu Kishi, Mitsuko Asai, Toru Masuda and Satoru Kuwada, 

 Chem. and Pharm. Bull. (Japan) 7 515 (1959). 



