CHEMICAL CONSTITUTION 



Oxidative degradation of a substance with this formula could 

 yield ^-carboxy-y-methyl butane sulphonic acid by the following 

 series of reactions : 



Treatment of model thio-ethers with lead tetra-acetate, however, did 

 not confirm the course of the above oxidation, since it gave a sulphone 

 and not a sulphoxide. 



The method of degradation used by du Vigneaud and his colleagues 

 with j8-biotin, however, should be capable of distinguishing between 

 the two possible formulae : {a) the pyrimidine formula, which should 

 give the triamine (I) with two amino groups on one carbon atom and 

 therefore yield an aldehyde by loss of ammonia ; and (b) the imidazo- 

 line formula which should give a stable triamine (II) : 



rr H2N— CH— CH 



H2N— CH— NH2 



I 



CH— S— CH, ""2 



1^ - - H,N— CH— CH. 



II , . CH.CH(CH3)2 



H2N— CH CH . CH(CH3)2 NH2 



(I) (11) 



F. Kogl and W. A. J. Borg ^^ therefore converted a-biotin methyl 

 ester into the hydrazide and then via the azide into the urethane. 

 This was hydrolysed with hydrochloric acid instead of baryta, the 

 agent used by du Vigneaud, in order to prevent splitting off of ammonia. 

 The product of this reaction proved to be a stable triamine, CgHigNgS, 

 identified as its picrolonate. 



This result was incompatible with the formula first proposed by 

 Kogl but consistent with his second formula, which is now generally 

 accepted, a- and jS-Biotin are therefore closely related substances, 

 which would be expected to exhibit comparable biological properties. 

 It would have been very surprising indeed to find such unique pro- 

 perties in two such unrelated molecules as those represented by du 

 Vigneaud's formula for j8-biotin and Kogl's original structure for 

 a-biotin. 



413 



