x-ray diffraction, electronic circular dichroism, and quantum mechanics (td-dft) investigations on 4-dehydroxyaltersolanol a, a secondary metabolite from endophytic fungus nigrospora oryzae

Background and objectives: a tetrahydro anthraquinone derivative, 4-dehydroxyaltersolanol a, has been obtained from nigrospora oryzae, which was isolated from uncaria borneensis havil as an endophytic fungus. this is a recently described compound whose stereochemistry was assumed from biogenetic considerations. however, using ecd spectral analysis in combination with td-dft calculations, its stereochemistry could be determined unambiguously. method: in the current research, the selected th1p45 culture was analysed using semi-preparative hplc, which led to the isolation of six secondary metabolites, including 4-dehydroxyaltersolanol a (1). we have further presented full evidence of the stereochemistry of compound 1. with the help of quantum calculations, we also determined the mechanism by which this compound degrades in solution. results: the analysis of th1p45 culture led to the isolation of six secondary metabolites, including 4-dehydroxyaltersolanol a, three anthraquinone derivatives (macrosporin, bostrycin and altersolanol b), and two pyrones (pestalopyrone and hydroxypestalopyrone). conclusion: a full evidence of the stereochemistry of compound 1 with the help of the combination of x-ray crystallography, ecd, and td-dft quantum calculations, allowed unambiguously assigning the absolute stereochemistry of 4 dehydroxyaltersolanol a as 1s,2r,3s as correctly assumed by proksh and collaborators from biogenetic considerations.