204 CAROTENOIDS CONTAINING HYRDOXYL GROUPS XI 



Derivatives 



Perhydroxanthophyll C40H78O2 : This compound is obtained by the catalytic 

 reduction of xanthophyll. It is a viscous, colourless oil which is weakly dextra- 

 rotatory^2° [ajp = +28° in chloroform. Perhydroxanthophyll is much more 

 soluble in organic solvents than xanthophyll, and can be esterified to give an 

 oily diacetate^^^. 



Xanthophyll halogenides: On treating xanthophyll with bromine, an oxygen-free 

 bromide C4oH4oBr22 is formed^22 -j-j-jg action of bromine dissolved in chloroform is 

 milder and only 8 mols are absorbed^^^. Using iodine chloride, ten double bonds 

 are saturated after 24 hours, but the eleventh double bond is only saturated after 

 7 daysi24. 



Xanthophyll diiodide C40H56O2I2 is a well-defined, beautifully crystalline 

 compound, the analysis of which confirms the molecular weight of xantho- 

 phylP^^. Xanthophyll is liberated unchanged from the iodide by means of 

 sodium thiosulphate^^^. 



Synthetic esters of xanthophyll^'^'' : The two hydroxyl groups in xanthophyll 

 can be esterified with acid anhydrides or acid chlorides in pyridine solution. 

 The spectral properties of xanthophyll and its esters are largely identical, but 

 in the partition test the esters show the opposite behaviour from xanthophyll 

 and are found quantitatively in the upper layer. The melting points of the 

 esters generally decrease with increasing length of the acid chain. The esters 

 are easily soluble in benzene and petroleum ether, but very sparingly in alcohols. 



a) Xanthophyll diacetate C44H60O4: Crystallises from a mixture of benzene and 

 methanol. M.p. 170°. 



b) Dipropionate C45H64O4: The dipropionate crystallises from a mixture of ben- 

 zene and methanol in reddish-yellow plates, m.p. 138°. 



c) Dibutyrate C48H68O4: Reddish-yellow plates from methanol. M.p. 156°. 



d) Di-n-valerate C50H72O4 : The ester crystallises from a mixture of benzene and 

 methanol in reddish-yellow plates, m.p. 128°. 



e. Di-ri-caproate €52^17504: Reddish-yellow plates from a mixture of benzene and 

 methanol. M.p. 117°. 



f) Dioenanthate C54Hgo04: Reddish-yellow plates from a mixture of benzene and 

 methanol. M.p. 111°. 



g) Dicaprylate C55H84O4: Reddish-yellow plates from a mixture of benzene and 

 methanol. M.p. 108°. 



h) Dipalmitate, Helenien, C^^^^j^^O^: 



This compound was discovered by Kuhn and Winterstein^^s [^ ^j-jg blossom 

 leaves of Helenimn autumnale. Helenien is widely distributed in the vegetable 

 kingdom. A summary of plants containing helenien is given by Kuhn and Winter- 



STEIN^^*. 



References p. 214— 2iy. 



