548 



BIOTIN 



OC 



NH— CH— CH2 



NH — CH— CH 



NH— CH— CH2 



OC 



\ 



NH— CH— CH 



(CHo)3-CHrBr 

 XXXII 



(CH2)3CH2C=N 

 XXXIII 



NH— CH— CH., 



OC 



s 



NH— CH— CH 



(CH2)4COOH 

 Biotin 



It was first claimed^" that in this synthesis three racemic isomers were 

 obtained, one of which was found to be identical with r/^biotin. Inasmuch 

 as the two other compounds did not yield either d/-desthiobiotin or dl- 

 allodesthiobiotin, it was later concluded^^ that they must be structurally, 

 and not only stereochemically, different from biotin. 



Another method of synthesis was described by Baker and his asso- 

 ciates.^^- ""®2 In one method the following series of steps was employed 

 (XXXIV-XLII). 



C2H500C-(CH2)4-C0C1— -^ CoH500C-(CH2)4CHO ™''^°°'*' 



acid 



XXXIV XXXV 



C2H600C(CH2)4CH:CHC00H-^ CHjOOC- (CH>)4CH:CHCOOCH3 

 XXXVI XXXVII 



HSCHjCOOCHj 



CH300C(CH2)4-CHCH2COOCH3 



I 

 SCH2COOCH3 



XXXVIII 



NaOCHj 



+ toluene 



" A. Grussner, J. P. Bourquin, and O. Schnider, Helv. Chini. Acta 29, 770 (1946). 

 " B. R. Baker, M. V. Querry, S. R. Safir, and S. Bernstein, J. Org. Chevi. 12, 13S 



(1947). 

 "*» G. B. Brown, B. R. Baker, S. Bernstein, and S. R. Safir. J. Org. Chcm. 12, 155 



(1947). 

 " G. B. Brown, M. D. Armstronf-, A. W. Mover, W. V. Onslow, B. R. Baker, M. V. 



Querry, S. Bernstein, and S. R. Safir, /. Org. Chcm. 12, 100 (1947). 

 6» B. R. Baker, IM. V. Querry, S. Bernstein, S. R. Safir, and Y. SuhbaRow, J. Org. 



Chem. 12, 167 (1947). 

 " B. R. Baker, M. V. Querry, S. R. Safir, W. L. McEwen, S. Bernstein, J. Org. Chcm. 



12, 174 (1947). 

 «2 B. R. Baker, M. V. Querry, W. L. McEwen, S. Bernstein, S. R. Safir, I.. Dortinan. 



and Y. SubbaRow, J. Org. Chem. 12, 186 (1947). 



