a-CAROTENE 



155 



Derivatives 

 "Dihydro-a-caroiene": 



By the reduction of a-carotene with aluminium amalgam, Karrer and Morf^**' 

 obtained a dihydro-a-carotene as a light yellow oil. The homogeneity and con- 

 stitution of this product is still uncertain. Degradation by means of ozone yields 

 geronic acid while on oxidation with potassium permanganate a : a-dimethyl- 

 glutaric acid is formed. 



Dihydroxy-a-carotene C4oH5g02 

 CH, CH3 



CH, 



CHo OHo 



CH, 



CH, 



CH, 



C 



CH2 C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH = C-CH=CH-CH CHj 



I ^OH I I 



I I/OH C CH2 



CH3 c /\/ 



\/'\ Dihydroxy-a-carotene(?) H3C CH 



CHj CH3 



Dihydroxy-a-carotene was obtained by Karrer and collaborators together 

 with a-semicarotenone and a-carotone during the oxidation of a-carotene with 

 chromic acid^^^. With regard to the constitution of this derivative, cf. Karrer, 

 VON EuLER and Solmssen^^^. The compound crystallises from a mixture of 

 methanol and petroleum ether in needles, m.p. 183° (uncorr.). Dihydroxy- 

 a-carotene is sparingly soluble in petroleum ether. It is dextrorotatory. Ac- 

 cording to Karrer, von Euler and Solmssen it has no vitamin A activity. 



Solvent: 



Carbon disulphide 



Senii-a-carotenone C40H58O2 : 

 OHo GH^ 



A bsorption maxima: 

 502 471 440 m/f 



CH, CH, 



\/ 



' CHo CHi CHo CHo C 



/\ I I I \ /\ 



CH, CO-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CH CH. 



CH2 CO-CH, 



\V 



CH, 



Semi-a-carotenone 



H,C-C 



CH, 



\ 



CH 



Semi-a-carotenone is formed by the oxidation of a-carotene with chromic 

 acid^^^ Semi-a-carotenone crystallises from methanol in needles, m.p. 135° 

 (uncorr.). The question of its constitution is dealt with in detail in the original 

 communication^^*. The fact that semi-a-carotenone has no vitamin A activity^^^ 

 is in agreement with the formula shown. 



Solvent: Absorption maxima: 



Carbon disulphide 533 499 mfj, 



Semi-a-carotenone mono-oxime C4oH5702Ni^® forms red crystals, m.p. 132". 

 References p. 165— lyo. 



