246 



BIOCHEMICAL SYSTEMATICS 



constitute modified terpenes perhaps most probably such of carene 

 type, seems inevitable." A naturally occurring tropolone, which may 

 serve as an example, is nootkatin, found in the heartwood of Chamae- 

 cyparis nootkatensis and Cupressus macrocarpa. 



0' OH 



nootkatin 



The tropolone nucleus itself is unusual, containing an unsat- 

 urated seven-membered ring: 



O OH 



tropolone 



Certain tropolone derivatives (for example, puberulonic and 

 stipitatic acids) have been described from the culture media of Peni- 

 cillium species, but chemically they are quite distinct from tropolones 

 of vascular plants. 



The hmited distribution of tropolone compounds plus the 

 somewhat unusual seven-carbon tropolone nucleus itself combine to 

 generate particular interest in the question of the biosynthesis of 

 these compounds. Present knowledge of their synthesis is based 

 principally upon the results of labehng experiments, utiHzing C^^, 

 followed by proposals for hypothetical mechanisms analogous to 

 some which have been established for other substances of biological 

 origin. Ferretti and Richards (1960), utiHzing C^^ labeled acetate, 

 formate, and glucose, have concluded that carbons 3, 5, 8, and either 

 1 or 7 are derived from the two-carbon of acetate while carbons 2, 4, 

 and 5 arise from the carboxyl of acetate. 



OH 



