1 55 Terpenoids and Steroids 



the principal mammalian sterol, cholesterol, has been worked 

 out. Good reviews of this work are available.' Many of the 

 proved intermediates in this route have been isolated from fungi, 

 and evidently the biogenesis of ergosterol and the triterpenes is 

 quite similar to that of cholesterol up to the later stages. ' 



The conversion of acetate to mevalonate follows the 

 course : " '^'^ 



CHsCO— S— CoA + CHaCOCHjCO— S— CoA -^ 

 Acetyl CoA Acetoacetyl CoA 



In the light of the newer knowledge concerning the role of 

 malonyl CoA in fatty acid biosynthesis there may eventually be 

 some minor modifications in this scheme. It should be men- 

 tioned that mevalonic acid has been shown to be an irreversible 

 intermediate in the biosynthesis of terpenoids.' "• ° 



Isopentenyl pyrophosphate, a further intermediate in the bio- 



* Louis F. Fieser and Mary Fleser, "Steroids," Reinhold Publishing 

 Corp., New York, 1959, pp. 403-420. 



•'^ Pierre Crabbe, Record of Chemical Progress 20 189 (1959). 



''J. W. Cornforth, R. H. Cornforth, A. Pelter, M. G. Horning and 

 G. Popjak, Tetrahedron 5 311 (1959). 



^^G. E. W. Wolstenholme and Maeve O'Conner (Eds.), "CIBA 

 Foundation Symposium on the Biosynthesis of Terpenes and 

 Sterols," Harry Rudney, The biosynthesis of P-hydroxy-fi-methyl- 

 glutaryl coezyme A and its conversion to mevalonic acid. Little, 

 Brown and Co., Boston, 1959, pp. 75-94. 



■ A. J. Birch, R. J. English, R. A. Massy-Westropp and Herchel 

 Smith, Proc. Chem. Soc, 233 (1957). 



^Idem., J. Chem. Soc, 369 (1958). 



^J. Fishman, E. R. H. Jones, G. Lowe and M. C. Whiting, Proc. 

 Chem. Soc, 127 (1959). 



