KARL FOLKERS 



racemates which have trans forms of the rings. The cis and trans 

 relationship of the rings is shown by structures XVI and XVII, re- 



(XVIII) 



spectively. Biotin is one of the eight stereoisomeric forms, dl- 

 Biotin and related cis and trans forms were obtained by Harris, Mozingo, 

 Wolf, Wilson, Arth, and Folkers (16). These other forms were des- 

 ignated ^/-allobiotin and (//-epiallobiotin. Grussner, Bourquin, and 

 Schnider (10) have described <//-pseudo-jS-biotin and ^/-iso-^-biotin 

 in addition to ^/-/S-biotin. Each group may have certain racemates 

 in common. Further work on the comparison of the properties and 

 degradation products of a-biotin and j8-biotin is apparently in progress, 

 according to a i-ecent paper by Kogl and Borg (27). 



Studies on synthesis provide interesting information concerning 

 the specificity of structure or the relationship between the constitution 

 and vitamin activity. The specificity of biotin has been discussed 

 in an excellent review article by Melville (31). Recent additions may 

 be made to the subject of specificity of biotin. The described cis and 

 trans forms related to ^/-biotin appear to be biologically inactive ac- 

 cording to Emerson (6), Ott (38), and Stokes and Gunness (54); see 



102 



