8 XANTHOPYHLL 205 



Helenien can be obtained synthetically from xanthophyll and palmitic acid 

 chloridei29 j^ crystallises from ethanol in red needles, m.p. 92°. With regard to the 

 colourimetric estimation, see Kuhn and Brockmann^^". 



i) Distearate C-j^-^^^i^i- ^^^ plates which appear yellow under the microscope. 

 M.p. 87°i3i. 



k) Dibenzoate C54H64O4: Red plates from ethanol. M.p. about 165°i3i_ 



1) Bis-/?-nitrobenzoate €54115208X2: This compound separates from benzene as a 

 red micro-cr^'stalline powder, m.p. 210°^^^. 



Xanthophyll monomethyl ether C4iH5802^^^: The ether is obtained from the 

 potassium derivative of xanthophyll (prepared by the interaction of xantho- 

 phyll and potassium ^^r^.-amylate) and methyl iodide. It crystallises from 

 methanol in needles, m.p. 150°. On partition between petroleum ether and 90 % 

 methanol the pigment exhibits predominately epiphasic behaviour, but both 

 layers are coloured. 



a-Citraurin CggHjoOg: 

 CHo CHo 



C CHo CH.. CHo CHo 



/\ I I I I 



CH2 CH- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CHO 



HOCH C-CHj 



\ ^ a-Citraurin 



CH 



a-Citraurin was obtained by Karrer, Koenig and Solmssen^^^ by the 

 careful potassium permanganate oxidation of xanthophyll. a-Citraurin is 

 related to /S-citraurin^^* in the same way as a-apo-2-carotenal to /9-apo-2- 

 carotenal. 



a-Citraurin crystallises from methanol in brilliant orange plates, m.p. 153°. 



Solvent Absorption maxima 



Carbon disulphide 514 480 449 m^ 



Petroleum ether 477 438 m^u 



Md = +372° (± 25°). (cf. Fig. 28, p. 359) 



Treatment of a-citraurin with hydroxylamine acetate affords the oxime, 

 which crystallises from methanol in clustered needles, m.p. 148°. 



Solvent Absorption maxima 



Carbon disulphide 499 468 m^u 



Ethanol 470 440 ran 



References p. 214-21"/. 



