CAROTENOIDS IN LAND PLANTS 



P-carotene varies from species to species but usually falls within the 

 range 200-700 fxg./g- dry weight. The carotene content of the leaves 

 of a large number of plant species has been collected in an appendix 

 (see p. 289). There is one report that p-carotene exists in timber (Acacia 

 acuminata). ^ ** 



The structure of p-carotene, which was finally elucidated by Karrer 

 and his colleagues,* is : 



Me 



-Me 



.^AAAy' 



Me Me 



p-carotene 



It is fitting to note here that Karrer ^^"^^ has crowned 20 years' 

 work on carotenoid chemistry by achieving a total synthesis of p- 

 carotene and lycopene (see p. 25), albeit in small yield. As this work 

 was reported after the publication of Karrer and Jucker's monograph, 

 the essential steps in the synthesis are included here, using p-carotene 

 as an example. 



CHj CH3 



CHj CH3 



CH=CH-t-CH2-CHCH + 4E + Mg8r 



OH 

 CH3 



CH, 



CHj 



CH, 



CH3 CHj 



■CH = CH-^C-CH2-C5CMgBr H- CCHj CH = CH.CH2.C + Mg Br CsC-CH2-C-CH=CH- 



XH, 



CH3 CH. 



OMgBr 



CHj 



CH3 



CHi 



CH, 



CH=CH-C-CH2-C = C-C.CH2.CH = CH.CH2-C-C2C-CH2-C-CH-CH 



OH 



OH 



^CH3 



CH3 CH3 



CHj 



CH3. 



6h 



CH3 CH3 



■CH=CH-C-GH2-CH=CH-C-CH2-CH = CH-CH2'-C-CH»CH-CH2-C-CH=CH ( 



^CH, 



CH3 



OH 



CHj 



OH 



OH 



HjO 



CHj 



CH3' 



CHj CH, 



cHj yy 



•CH»CH.C=Cri-CH=CH-C = CH-CH=CH-CH = C-CH = CH-CH=C-CH = CH — {\ 



^CHj 



CHjA/ 



