Naphthol radical couplings determine structuralfeatures and enantiomeric excess of dalesconolsin Daldinia eschscholzii

摘要

Understanding how simple molecules are pieced together in organisms may aidbiotechnological manipulation and synthetic approaches to complex natural products. Themantis-associated fungus Daldinia eschscholzii IFB-TL01 produces the unusually structuredimmunosuppressants (±)-dalesconols A and B, along with their congener (±)-dalesconol C,with the (-)-enantiomers in excess. Here we report that these structural and stereochemicalpeculiarities of dalesconols A–C are a result of promiscuous and atropselective couplingsof radicals derived from 1,3,6,8-tetrahydroxynaphthalene, 1,3,8-trihydroxynaphthalene and1,8-dihydroxynaphthalene. The observed (-)-enantiomeric excess is found to depend on thedominance of particular conformers of naphthol dimer intermediates, which are ligands oflaccase.