Example VII A mixture of 20 cc. of dimethyl sulfoxide and cc. of recently distilled boron trifluoride etherate was heated under anhydrous conditions and with slow distillation until reaching an approximate temperature of 174 C.; it was then cooled and 5 g. of A -pregnen-20 8-ol-3-one and 4 g. of paraformaldehyde were added, and the reaction mixture was heated in an oil bath at 160 C. for 2 hours. It was cooled, poured into ice water and eX- tracted with ethylacetate, the organic extract was washed with water to neutral, dried over anhydrous sodium sulfate and evaporated to dryness under reduced pressure.
Structural transformation of anticancer drug exemestane (1) with fungi Cunninghamella blakesleeana (ATCC 8688A), Curvularia lunata (ATCC 12017), Aspergillus niger (ATCC 10549), and Gibberella fujikuroi (ATCC 10704) yielded eleven metabolites 2-12, in which 2 and 8 were identified as new. Their structures were characterized as 6-methylene-5α-androstane-3β,16β,17β-triol (2), 17β-hydroxy-6-methyleneandrosta-4-ene-3-one (3), 6α-spiroxirandrost-4-ene-3,17-dione (4), 6-methyleneandrosta-4-ene-3,17-dione (5), 6β,17β-dihydroxyandrost-4-en-3-one (6), 17β-hydroxy-6α-spiroxirandrost-1,4-diene-3-one (7), 17β-hydroxy-6α-hydroxymethylandrosta-1,4-dien-3-one (8), 6α-hydroxymethylandrosta-1,4-diene-3,17-dione (9), 17β-hydroxy-6-methyleneandrosta-1,4-diene-3,16-dione (10), 6α-hydroxy-4-androstene-3,17-dione (11), and 6α-hydroxymethylandrost-4-ene-3,17-dione (12). Substrate 1, and its transformed products were evaluated for their cytotoxicity against breast cancer cell line (MCF-7). Compound 3 was found to be moderately active with an IC 50 of ±μM, in comparison to the standard anti-cancer drug, doxorubicin (IC 50 =±μM).