Assignment of the Absolute Configuration of(+)-Diplopyrone,the Main Phytotoxin Produced by Diplodia mutila,the Pathogen of the Cork Oak Decline,by a Nonempirical Analysis of Its Chiroptical Properties

摘要

The nonempirical assignment of the absolute configuration of(+)-diplopyrone,the main phytotoxin of Diplodia mutila,i.e.,an endophytic fungus,widespread in Sardinian oak forests,and considered one of the main causes of cork oak decline,has been approached by two different methods:(a)the exciton analysis of the circular dichroism(CD)spectrum and(b)the ab initio calculation of the optical rotatory power.Both methods indicate that(+)-diplopyrone is 6-[(1S)-l1-hydroxyethyl]-2,-4a(S),6(beta),8a(S)-tetrahydropyrano[3,2-b]pyran-2-one,so the stereostructure of this important biomolecule is safely determined for the first time.A comparison of advantages and limitations of the two methods of analysis is also presented.