183 Tropolone Acids 



stipitatonic acids remains undetermined. It, too, may arise 

 from formate. A study has been made" of the enzymatic de- 

 carboxylation of stipitatonic and puberulonic acids. A biochem- 

 ical relationship was concluded by way of this enzyme, and the 

 suggestion made that the intermediate tropolone precursors 

 must be at least C., compounds, and that direct closure of an 

 acyclic to a seven-membered ring structure must occur. 



The results of Richards and Ferretti seem to leave it an open 

 question as to whether the tropolone ring is formed by direct 

 cyclization of a long-chain acyclic compound or by expansion 

 of a six-membered ring, and the exact nature of the interme- 

 diate precursors of this interesting series of mold metabolites 

 remains a mystery. 



372 Stipitatic Acid, CsHgOs, pale yellow plates, m.p. 282° (dec). 



COOH 



Penicillium stipitatum Thom 



J. R. Bartels-Keith, A. W. Johnson and W. I. Taylor, J. 

 Chem. Soc, 2352 (1951). (Synthesis) 



Peter L. Pauson, Chem. Revs. 55 9 (1955). (A review of 

 tropolones ) 



373 Puberulic Acid, CsH^O,;, nearly colorless plates, m.p. 318°. 



O OH 



COOH 



Penicillium puberulum Bainier, P. aurantio-virens 

 Biourge, P. cyclopium-viridicatum and P. johannioli Za- 

 leski 



R. E. Corbett, C. H. Hassall, A. W. Johnson and A. R. Todd, 

 /. Chem. Soc, 1 (1950). 



Ronald Bentley and Clara P. Thiessen, Nature 184 552 (1959). 



