I BIXIN 261 



CH3 CH3 CH3 



I I I 



HjCOOC- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CHO 



III 

 CH3 CH3 H H CH3 



H,COOC-CH C CH C CH CH C=C C CH-COOH 



CH CH CH CH CH C CH CH 



Labile bixin CHs 



CHq CH^ 



I ! 



HjCOOC-CH C CH C CH CH CH CH CH 



CH CH CH CH CH C CH C CH-COOH 



Stable bixin CH3 CH3 



The stereochemical configuration of the bixins has recently been investigated 

 by Zechmeister and Escue^'. Instead of natural, labile bixin they chose the 

 more easily chromatographed labile methylbixin for investigation, and sub- 

 jected it to heat treatment, iodine catalysis and illumination with sunlight. 

 These experiments yielded a number of transformation products, two of which, 

 neomethylbixin A and neomethylbixin C, were obtained in a crystalline state. 

 The other isomers could be distinguished by their optical properties. 



Neomethylbixin A crystallises from a mixture of benzene and methanol in long, 

 narrow plates, m.p. 190-192° (corr.). It is more soluble and less stable than labile 

 methyl bixin and exhibits maxima at 485 and 453 m^ in petroleum ether solution. 

 Neomethylbixin C is obtained from a mixture of benzene and methanol in small, 

 clustered needles, m.p. 150-151° (corr.). It exhibits absorption maxima at 479 and 

 448.5 m/z in petroleum ether solution. 



1. Stable norbixin C24H28O4: 



CH3 CH3 CH3 CH3 



HOOC- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CH=CH- COOH 



Norbixin 



The potassium salt of stable norbixin is obtained by boiling labile bixin 

 with excess 10 % potassium hydroxide. The free acid separated on addition of 

 hydrochloric acid to the aqueous solution^^. The dinitrile of norbixin can be 

 obtained from bixin dialdehyde dioxime (cf. under lycopene, pp. 118 and 123) 

 and yields norbixin on hydrolysis with methanolic potassium hydroxide. 



Stable norbixin crystallises from pyridine in glistening blue-red leaflets. 

 It does not melt below 300°. It is fairly easily soluble in pyridine, very sparingly 

 soluble in acetic acid and amyl alcohol, and almost insoluble in other organic 

 solvents. 

 References p. 2go-2g4. 



