BIXIN 259 



CHj CH3 



BrCHaCHCHjCHaCHijCHCHjBr 



+ 2 NaCH(COOR)a 



CH3 I CHs 



(ROOQaCHCHjCHCHaCHjCHijCHCHaCHCCOOR)^ 



CH, 



CH, 



HOOC- CHjCHaCHCHaCHjCHaCHCHaCHa- COOH 



CH, 



CH, 



ROOC-CHjCHaCHCHjCHaCHaCHCHjCHjCOOH 



Electrolysis 



OHo OHo 



CH, CH, 



ROOC- CHaCHjCHCH^CHjCHaCHCHaCHaCHaCHjCHCHaCHjiCHaCHCHjCHa- COOR 



CH, CH, 



CH, CH, 



HOOC- CHaCHaCHCHjCHaCHaCHCHjCHjCHaCHjCHCHaCHjCHjCHCHaCH,- COOH 

 Perhydronorbixin 



With regard to the conversion of perhydrocrocetin into perhydronorbixin, 

 see p.. 278. 



Stereochemistry of Bixin 



The first observation concerning a stereoisomer of bixin was made in 1913. In 

 the course of the isolation of the pigment, Herzig and Faltis^^ accidentally 

 obtained a new, higher melting form which they termed /3-bixin. It was later 

 suggested by Karrer and collaborators^^, that the two forms may be cis-trans 

 isomers. By the treatment of natural labile bixin with iodine^*, these workers 

 obtained the stable form identical with the j3-bixin of Herzig and Faltis. 

 The same transformation was also achieved with methyl bixin (p. 268) . It was 

 thus shown that two series of compounds exist, one of which is derived from the 

 labile natural bixin, and the other from the stable jS-bixin. A uniform nomen- 

 clature for bixin derivatives was proposed by Karrer and Kuhn and is em- 

 ployed in the sequel. 

 References p. 2go-2g4. 



