10 



Tropolone Acids 



The detailed biosynthetic origin of the tropolone acids remains 

 obscure. Various suggestions have been made. One of these^' ^ 

 proposed enlargement of the aromatic ring of 3,5-dihydroxy- 

 phthalic acid, a known mold metabolite: 



HO 



COOH 



CH2O 



OH 



COOH 



HO 



HOCH; 



COOH 



lO] 



COOH 



OH 

 HO COOH 



HO 



/"^X COOH 

 O OH 



/ 



COOH 



OH 



Another^ proposed enlargement of an alicyclic ring in a Cg — C3 

 type of intermediate from the shikimic acid route: 



CO— COOH 



HOOC CH2COCOOH HOOC CH 



[O] K^ [O] 

 lO] 



10]^^[0] 

 [O] 



IT. R. Seshadri, /. Sci. Ind. Research (India) 14B 248 (1955). 

 ^ R. Robinson, "The Structural Relations of Natural Products, 

 Oxford Univ. Press, London, 1955. 



3 A. J. Birch, Fortschr. Chem. org. Naturstaffe 14 186 (1957^ 



