i88 CAROTENOIDS CONTAINING HYRDOXYL GROUPS XI 



Derivatives of Physalien 



a) Perhydrophysalien C72Hj3g04: A colourless oil, easily soluble in ether, 

 sparingly in ethanol. 



b) Physalien iodide: This compound is formed by treating an ethereal 

 solution of the pigment with an ethereal solution of iodine. On treating the 

 addition product with thiosulphate, unchanged physalien is regenerated. 



c) Physalienone: By the treatment of physalien with chromium trioxide, 

 Karrer, Solmssen and Walker^° obtained a tetraketone of the following 

 constitution (cf. Karrer and Gugelmann^^) : 



CH3 CH3 CH3 CH3 



C CHo CHo CHq CHo C 



/\ 1 11 \ /\ 



CH2 CO-CH=CHC=CHCH=CHC=CHCH=CHCH=CCH=CHCH=CCH=CH-OC CHj 



CisHsiCOO-CH CO-CHs HjC-OC CH-OOC-CisHsi 



\^ / Physalienone \ / 



CH2 CH2 



The tetraketone crystallises in clustered needles, m.p. 144-145°. Its optical 

 properties are very similar to those of ^-carotenone. 



Solvent: Absorption maxima: 



Physalienone p-Carotenone 



Carbon disulphide .... 536 500 463 538 499 466 m/z 



Petroleum ether 497 464 436 502 468 440 ni/^ 



Chloroform 525 488 452 527 489 454 m^t 



With regard to the action of bromine on physalien, cf. Zechmeister and 

 VON Cholnoky^^. With regard to the reaction with iodine, cf. Kuhn and co- 

 workers®^. The assimilation of physalien by rats and chicks has been investi- 

 gated by Kuhn and Brockmann®*. 



Cis-trans Isomers of Zeaxanthin 



By a variety of treatments, such as heating in solution, dissolution of the 

 crystals, catalysis with iodine and illumination with sunlight, Zechmeister 

 and co-workers converted zeaxanthin into mixtures of different pigments which 

 they regard as cis-trans isomers®^. Three compounds could be obtained in the 

 crystalline state, namely neo-zeaxanthin A, neo-zeaxanthin B and neo- 

 zeaxanthin C. Another pigment different in character from the other isomers 

 is also formed®^. Treatment of this compound with iodine (except in alcohol 

 solution) results in a displacement of the absorption maxima towards shorter 

 wavelength by 2-4 m.[_i. 



The three crystalline neo-zeaxanthins have the following properties : 

 References p. 214— 2iy. 



