BIOTIN 



a-Isopropyl-5-methyl-2-iniidazolidone-4-propionic acid, the struc- 

 tural isomer of desthiobiotin corresponding to Kogl's revised formula 

 for a-biotin (page 412), had neither growth-promoting activity towards 

 S. cerevisiae or L. helveticus nor anti-biotin activity towards L. hel- 

 veticus.^^ 



The higher homologue of desthiobiotin, homodesthiobiotin was 

 synthesised by the following route : 2' 



^^^^^ C.H.OOC.(CH,),.CO.CH, ^^^^ 



Ha KCNO 



CH3 — ^ C^H^OOC . (CH2)e . CH . CO . CH3 



NHj 



CO 

 H2O 



NH NH 



II =' I I 



C=C (CH2)e . COOQH5 CH3 . CH CH . (CH2)e . COOH 



It was devoid of biotin activity when tested on 5. cerevisiae but had 

 anti-biotin activity (page 452). A method similar to the above was 

 also used for the preparation of desthiobiotin. 



Two other homologues of desthiobiotin, 2-imidazolidone-4-w-hexoic 

 acid and 5-ethyl-2-imidazolidone-4-M-hexoic acid, were also without 

 biotin activity towards S. cerevisiae and L. helveticus}^ They anta- 

 gonised the growth-promoting effect of biotin, however (page 452). 



Oxyblotin 



Oxy biotin ^^ or O-heterobiotin, one of the four possible racemic 

 forms of 2'-keto-imidazolidino-(4' : 5' : 3 : 4)-tetrahydrofuran-2-w-valeric 

 acid was synthesised by the route ^^ shown on opposite page. 



According to Duschinsky et al}^ oxybiotin had 25 % of the growth- 

 promoting activity of ^-biotin towards L, helveticus or Saccharomyces 

 cerevisiae and, according to Pilgrim et al.,^'^* ^^ 50 % of the activity of 

 ^-biotin towards L. arabinosus, 40 % towards L. helveticus, 15 % 

 towards Rhizobium trifolii and 25 and 8 % towards S. cerevisiae when 

 compared at half maximal and maximal growth respectively. 



Rubin et al.^ foimd it to have 28 % of the activity of biotin for 

 S. cerevisiae (5 strains) and L. helveticus, and 50 % for L. arabinosus. 

 They also found that it was inactivated by avidin in the same stoichio- 

 metric proportions as was biotin, whilst its growth-promoting action 

 on L. helveticus was inhibited by desthiobiotin. Oxybiotin could 

 replace biotin as a growth factor for several Clostridia, ^^ and for 

 Lactobacillus pentosus^^^ 



Oxybiotin can be estimated by comparing the growth produced in 



450 



