II. CHEMISTRY 



329 



nor its o'-phosphatc, even in a 1000-fold excess o\cv liWoflaxiii, has an 

 inlhuMicc on the activity of n-aniino acid oxidase or xanthine oxidase.'""" 



OH OH OH 



I I I 

 CH2— C— C— C— CHjOH 



III 

 H H H 



CI 



CI 



N N 



CO 



NH 



N CO 



Dichloroflavin 



OH H OH OH 



I I I I 

 CHo— C— C— C— C— CH .OH 



I I I I 

 H OH H H 



CI 



CI 



/\/ 



N 



N 



\ 



CO 



NH 



II 



N CO 



Dichloro-D-sorboflavin 



For one substance of this type, 6,7-dichloro-9-(l'-D-sorbityl)isoallox- 

 azine (II), a special biological effect has been observed. ^^ It exhibits no 

 significant inhibition of riboflavin microbiologically and in vivo in rats. 

 However, it is effective in producing regression of established lympho- 

 sarcoma implants in mice. The D-ribityl, L-arabityl, and D-dulcityl analogs 

 of compound II show, respectively, slight, questionable, and no carcinolytic 

 activity. 6-Chloro-9-(l'-D-sorbityl)isoalloxazine appeared to have some ac- 

 tivity in several tests. Other riboflavin analogs in which the substituents 

 in the 6 and 9 positions were varied gave questionable or negative results. 



Lettr^'"^'' first demonstrated that certain flavins, which are antagonists 

 of riboflavin, have an antimitotic effect. Later, regression of lymphosarcoma 

 and decreased growth rate of spontaneous mammary carcinomas in mice 



'»«» P. Karrer and H. Ruckstuhl, Bull, schweiz. Akad. med. Wiss. 1, 236 (1945). 

 I'sb H. Lettrd, Angexv. Chem. 53, 363 (1940); H. Lettr6 and M. E. Fornliolz, Rcr. 73, 

 436 (1940). 



