Metabolic fate of 3α,5-cycloandrostanes in the endogenous lactonization pathway of Aspergillus tamarii KITA

Transformed 3α,5-cyclosteroids undergo ring-D lactonization or hydroxylation. The 15β-hydroxyl inhibits entrance into the lactonization pathway. Presence of C-17 ketone was essential to gain access to 15β-hydroxylation pathway.