Pfizer Handbook of Microbial Metabolites 404 



Akermark H. Erdtman and C. A. Wachtmeister, Acta Chem. 

 Scand. 13 1855 (1959). (Structure) 



860 d- and MJsnic Acid, CjsHieOj, yellow crystals, m.p. 203°, [ixW 

 (d-form) +492°, (Z-form) -495°. M.p. d,Z-form 195°. 



CH3 



Usnea, Alectoria, Ramalina, Evernia, Cetraria, Parmelia, 

 Cladonia, Lecanora and Haematormna species (most yel- 

 low lichens). Long known. 



Both d- and Z-forms occur in lichens. Relatively high 

 yields are available from some species. 



Clemens Schdpf and Friedrich Ross, Naturivissenschaften 

 26 772 (1938). 



Idem., Ann. 546 1 (1941). (Structure) 



D. H. R. Barton, A. M. Deflorin, O. E. Edwards and J. B. 

 Hendrickson, Chem. and Ind., 1670 (1955). (Synthesis) 



861 Didymic Acid (Incrassatic Acid), C22H26O5, colorless crystals, 

 m.p. 172°. 



C3H7 C5H11 _^_,, 



I I COOH 



CH3O OH 



Cladonia species (occurs together with squamatic and 

 barbatic acids) 



Yasuhiko Asahina and Masaru Aoki, /. Pharm. Soc. Japan 

 64 41 (1944). 



C. PYRANS AND RELATED SUBSTANCES 

 The y-Pyrones and Patulin 



The biosynthesis of patulin was discussed in the intro- 

 duction to the chapter on phenolic substances. 



Kojic acid has long attracted interest because it is pro- 

 duced in such high yields by certain Aspergillus species. 

 Within the past few years isokojic acid and several other 

 related y-pyrones have been isolated from Gluconoaceto- 

 bacter cultures. 



