540 VI. CAROTENOIDS AND RELATED COMPOUNDS 



accumulate in lipid material where possible. A summary of other sources 

 of lycopene is given by Karrer and Jucker.-* 



c. Related Compounds. There are several important derivatives in 

 which the carbon chain has remained intact. A number of oxidation 

 products are also well known in which varying numbers of carbon atoms 

 have been split from the chain. 



(a) Prolycopene, C40H56. The most interesting of the lycopene deriva- 

 tives is probably prolycopene, which is a poly-as compound discovered by 

 Zechmeister et aL^^"-^*^ in the tangerine tomato {Lycopersicon esculentum) . 

 It is one of the rare examples of carotenoid pigments occurring naturally 

 which does not have the all-^rans structure. The new pigment was shown 

 to have a wide distribution since it occurred in the palm fruits (Butia 

 capitataY^^ and {Butia eriospatha Becc.),-* in the narrow-leaf firethorn 

 (Pyracantha angustifolia) ,^^ in the euonymus (Euonymus fortunei Rehd.),^^^ 

 and in the monkey flower {Mimulus longiflorus Grant). ^'^ 



Prolycopene has been shown to be 1,3,5,7,9,11-CTS-lycopene.-''- On 

 iodine catalysis, a complicated mixture results, from which ordinary all- 

 /rans-lycopene can be separated. Prolycopene crystallizes from petroleum 

 ether and ethanol in plates which melt at 111°C. It is more readily soluble 

 than is lycopene in various organic solvents. Zechmeister and Pinckard^^" 

 have reported the presence of at least 6 different poly-as-lycopenes in the 

 extract from the ripe berries of the Pyracantha angustifolia Schneid. 



(b) Perhydrolycopene, C40H82. When lycopene is hydrogenated cata- 

 lytically, it adds 13 molecules of hydrogen to form the saturated hydrocar- 

 bon.-^* The same compound has been synthesized from dihydrophytol by 

 Karrer and his collaborators. ^^^ It is a colorless oil boiling at 238-240°C. 

 at 0.3 mm., having a density at 18° of 0.822 and a refractive index of 

 1.4560. 



(c) Dehydrolycopene, C40H62. Karrer and Rutschmann-^^ prepared 

 this compound by removing 4 hydrogen atoms from lycopene by the use 

 of bromosuccinimide. The new product has 15 conjugated double bonds. 

 It is only slightly soluble in most solvents, but it dissolves sufficiently in 

 pyridine to enable one to crystallize it. The crystals appear dark violet to 

 black. They are gradually decomposed at 200°C. 



(d) Apo-2-lycopenal, C32H42O. The older designation for this compound 

 was lycopenal. However, because several closely related substances are 

 now known, the new terminology is preferable for differentiation. 



-^^ L. Zechiaeisler, A. L. Le Rosen, F. W. Went, and L. Pauling, Proc. NatL Acad. 

 Sci., 27, 468-474 (1941). 



2" A. L. Le Rosen and L. Zechmeister, J. Am. Chem. Soc, 64, 1075-1079 (1942). 



-" L. Zechmeister, A. L. Le Rosen, W. A. Schroeder, A. Polgdr, and L. PauUng, 

 J. Atn. Chem. Soc, 6V7, 1940-1951 (1943). 



2" P. Karrer, A. HeltVnstein, and R. Widmer, Helv. Chim.. Acta, 11, 1201-1209 (1928). 



"^ P, Karrer and J. Rutschmann, Helv. Chim. Acta, 28, 793-795 (1945). 



