250 CAROTENOIDS CONTAINING CARBONYL GROUPS XII 



The compound crystallises from a mixture of benzene and petroleum ether 

 in leaflets and needles, m.p. 189° (uncorr., in vacuum). On shaking the ethereal 

 solution of the pigment with concentrated aqueous hydrochloric acid, the latter 

 assumes an unstable deep blue colouration. In the partition test the pigment is 

 found quantitatively in the lower layer. 



On treating capsanthin epoxide with very dilute hydrochloric acid, it is 

 isomerised into the stabler furanoid oxide, capsochrome. 



CHj CII3 

 CH CH, CH, CH, CH, C 



II I I I /\ 



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



I 



HaC-CHj CHOH 

 Capsochrome \ / 



CHj 



Capsochrome crystallises well from a mixture of benzene and petroleum 

 ether. Melting point 195° (uncorr., in vacuum). The pigment exhibits the same 

 behaviour towards hydrochloric acid as capsanthin epoxide. It is hypophasic 

 on partition between methanol and petroleum ether. 



Solvent Absorption maxima 



Capsanthin epoxide Capsochrome 

 Carbon disulphide 534 499 515 482 m/i 



Chloroform 511 481 492 462 m/i (not sharp) 



Benzene 514 483 496 464 m^ 



Partially Synthetic Polyene Ketone Containing the Chromophoric 

 System of Capsanthin 



By condensing j3-apo-2-carotenal^*'^ (I) with pinacolone (II), Karrer and 

 JuCKER^*^' obtained the polyene ketone (III) which possesses the same chromo- 

 phoric system as is present, according to Zechmeister and von Cholnoky^"^, 

 in capsanthin. The absorption bands of the two pigments in the visible region 

 are completely identical, which supports the formula proposed for capsanthin. 



\/ 



L/Ho CHo CHo CHo 



/\ I I I I 



CHj C- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CHO+CHsCO- C(CH3)j 



CHo C" CHo 



\/ I . II 



CHj 



References p. 253—253. 



