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DOI: 10.1055/s-0028-1084483
Relative and absolute configurations of azaphilones isolated from the Brazilian endophytic fungus Chaetomium globosum
In the course of our continuous search for secondary metabolites from endophytic fungi associated with Asteraceae species, Chaetomium globosum (VR10), isolated from Viguiera robusta, was cultivated on PDB medium for twenty-one days. The EtOAc extract from the culture broth was submitted to several chromatography procedures, including HPLC. Ten azaphilones have been isolated and characterized by HRMS, 1D and 2D NMR methods. Four derivatives belong to group 1, two derivatives belong to group 2, two derivatives belong to group 3, and two derivatives belong to group 4. Chaetoviridins A-D have already been isolated from another strain of C. globosum,1 while the others (named chaetoviridins E-J) are being described for the first time. The azaphilones represent a structurally diverse class of poliketide natural products containing a pyrano-quinone structure. This communication will discuss the determination of the relative configuration of some stereogenic centers by NOE-diff experiments and the absolute configuration by the modified Mosher's derivatization using MPA. Basic structures of groups 1–4 are shown below:
Acknowledgements: Financial support from Brazilian agencies Capes, CNPq and Fapesp.
References: 1. Takahashi, K. et al. (1990) Chem. Pharm. Bull. 38: 625–628