^-CAROTENE 147 



Mutaiochrome C40H55O' 

 CHo CHo 



CHo CHo 



\V 



CH CH3 CH3 CH3 CH3 C 



CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CH=CH- C CHj 

 Mutatochrome = Citroxanthin C CH, 



/\/ 



H3G CH2 



By the action of hydrogen chloride on /5-carotene mono-epoxide, the 

 corresponding furanoid oxide, mutatochrome is formed, together with a small 

 proportion of |5-carotene. Mutatochrome crystallises from a mixture of benzene 

 and methanol in yellow-orange leaflets, m.p. 163-164° (uncorr., in vacuum), 

 Mutatochrome behaves in the same way as /S-carotene mono-epoxide in the 

 hydrochloric reaction and partition test. 



Solvent: Absorption maxima: 



Carbon disulphide 489.5 459 m/i 



Benzene 470 440 m/i 



Petroleum ether 456 427 m/z 



Chloroform 469 438 m/z 



Aurochrome CioHjgOj: 



CH, CH, CH3 CH, 



C C 



CHa C=CH CH3 CH3 CH3 H3C CH=C CH2 



CHo C CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH C CH, 



.CH2I • Aurochrome \ CHg 



CH3 H3C 



Aurochrome is formed by the action of dilute hydrochloric acid on /5-caro- 

 tene di-epoxide. It crystallises from a mixture of benzene and methanol in 

 beautiful yellow leaflets, m.p. 185° (uncorr., in vacuum). On adding con- 

 centrated aqueous hydrochloric acid to an ethereal solution of this pigment, a 

 very stable dark blue colouration is formed. On partitioning aurochrome 



By the action of perbenzoic acid on ^-carotene, H. v. Euler, P. Karrer and O. 

 Walker, {Helv. chim. Acta 15 (1932) 1507) obtained an oxide which they formulated as 

 /5-carotene mono-epoxide. These authors were unaware of the great sensitivy of this com- 

 pound to acids and later comparison has shown that they had in fact obtained the furanoid 

 oxide, mutatochrome, and not the mono-epoxide formed primarily. P. Karrer and E. 

 JucKER, Helv. chim. Acta 30 (1947) 536 established the identity of mutatochrome with 

 the pigment citroxanthin which they had isolated from orange peel {Helv. chim. Acta 2j 

 (1944) 1695). Mutatochrome is thus a naturally occurring pigment. 



References p. 16^—iyo. 



