Biotransformations of jhanol (18-hydroxymanoyl oxide) (2), jhanidiol (1beta,18-dihydroxymanoyl oxide) (3), and 1-oxo-jhanol (1-oxo-18-hydroxymanoyl oxide) (4) by the fungus Mucor plumbeus have been studied. In the incubation of 2 there exists a preference for hydroxylation at C-2(alpha) (8) and C-6(beta) (9-11) and, to a lesser degree, at C-1(alpha) (7), C-11(alpha) (6), and C-11(beta) (5 and 10). In the second substrate (3), the presence of a 1beta-hydroxyl group inhibits 6beta- or 11-hydroxylation. Epoxidation of the vinyl group constitutes the main reaction, with the positions 2alpha (14) and 3beta (15) being hydroxylated. In the incubation of 4, there was a preference for 6beta-hydroxylation (21) or epoxidation of the vinyl group (22). Other hydroxylations observed were at the 2alpha (19), 2beta (20), 3alpha (23), 3beta (24), and 11beta (18) positions.

The incubation of 3α,15β-dihydroxy-ent-kaur-16-ene (1) with the fungus Gibberella fujikuroi gave 3α,7α,15β-trihydroxy-ent-kaur-16-ene (5), 3α,11β,15β-trihydroxy-ent-kaur-16-ene (13), and 3α,7α,11β,15β-tetrahydroxy-ent-kaur-16-ene (17). The ether 3α,15β-dihydroxy-11β,16β-epoxy-ent-kaurane (15) and the isomerized compounds 3α,7α-dihydroxy-15-oxo-ent-(16S)-kaurane (8) and 3α,7α,11β-trihydroxy-15-oxo-ent-(16S)-kaurane (10) were also obtained. The incubation of 3α-hydroxy-15-oxo-ent-(16S)-kaurane (7) with the fungus also afforded compounds 8 and 10, as well as 3α,11β-dihydroxy-15-oxo-ent-(16S)-kaurane (20), 3α,6α,11β-trihydroxy-15-oxo-ent-(16S)-kaurane, (22) 3α,6β,7α-trihydroxy-15-oxo-ent-(16S)-kaurane (25), and 3α,11β,16α-trihydroxy-15-oxo-ent-(16S)-kaurane (27). These results indicate that in 3,15-oxygenated ent-kaurane derivatives the presence of a 3α-hydroxyl inhibits oxidation at C-19, while a 15β-hydroxyl or a 15-oxo group directs hydroxylation at C-11(β) and C-7(α).

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