Biotransformation of a 4α-hydroxylated eudesmane with Exserohilum halodes: Chemo-enzymatic synthesis of cryptomeridiol and 6-epi-colartin derivatives

Microbial transformation of a 4α-hydroxylated eudesmane by Exserohilum halodes has been achieved. Regioselective hydroxylations in both “A” and “B” rings, on C-2 and C-8, were detected, but the main hydroxylating action was directed to the isopropyl moiety and cryptomeridiol analogues were isolated. Semi-synthesis of two sesquiterpenolides, 6-epi-colartin derivatives, were accomplished from the significant metabolites hydroxylated at C-12.