6 CAPSANTHIN 249 



By applying the usual methods (cf. p. 39), it is possible to isomerise capsanthin 

 and capsanthin dipalmitate^^^ into various compounds which according to 

 Zechmeister and von Cholnoky^"^ and PolgAr and Zechmeister^*'* are cis- 

 trans isomers of the two pigments. Neo-capsanthin A could be obtained in a 

 micro-crystalhne form, but no data are available regarding its melting point 

 and elementary analysis. 



Solvent Absorption maxima 



Neo-A Neo-B Neo-C 



Carbon disulphide . . (532) (495) m^ 



Benzene (513) (481) m/f (513) (481) m,u (508) (479) m^ 



Hexane 496 465 m/^ 



The different isomers have the following optical rotations in benzene : 



Capsanthin [a\ = ± 0°(±5-10°) 



Neocapsanthin A [aJc = + 89° 



Neocapsanthin B [a]c = + 21° (± 5°) 



Neocapsanthin C [aj^ = + 27° ( ± 10°) 



Analogous experiments with capsanthin dipalmitate gave rise to two trans- 

 formation products which exhibited the following absorption maxima : 



Carbon disulphide Benzene Hexane 



Capsanthin dipalmitate 541.5 502 m^ (519) (488) m/x 506 473 m/i 



Neocapsanthin dipalmitate I 535 499 m^< (512) (483) m/z 502 470 m/^ 



Neocapsanthin dipalmitate II 533 497 m/i (510) (482) m/i 496 465 m/z 



Optical rotations in petrol: 



Capsanthin dipalmitate [aj^ = —30° 



Neocapsanthin dipalmitate I [a],, = -22° 



Neocapsanthin dipalmitate II [a\ = -20° 



After iodine catalysis, the neo-capsanthins exhibit a well defined 'cis-peak' 

 near 363 m^ in petrol. 



The possible configurations of the different isomers are discussed by Polgar 

 and ZechmeisterI"*. 



Capsanthin mono-epoxide and Capsochrome 



Karrer and Jucker^"^ subjected capsanthin diacetate to oxidation with 

 monoperphthalic acid and obtained a crystalline mono-epoxide C40H58O4: 



CH3 CHo CHo CHo 



C CHo CHo Clio CHo C 



/\ I I I r /\ 



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



)0 ' 



HaC-CH, CHOH 

 HOCH C-CHs • \/ 



\^ / Capsanthin epoxide CH, 



CH2 



References p. 25J-255. 



