the photoreaction of flavoquinones ( lumiflavin , riboflavin , fmn etc . and their 3-alkylated derivatives ) with propargylamine-type acetylenic substrates , r4 -calpha identical to cbeta -cgammahr3 -nr2r1 , yields a mixture of two adducts , which result from covalent calpha fixation of the cgamma-deprotonated substrate to either position c ( 4a ) or n ( 5 ) in the flavin nucleus .
C0035527
riboflavin
C0016388
fmn