In the ent-beyerane series, predominant hydride attack of a carbonyl at C-2 or C-3 from the less hindered ent-a-face is well established by analogy to similar terpenoid systems-see ref.9a.

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Sumwary A double 1,2-rearrangement of a 12-oxo-beyer-15( 16)-ene system across the 12,13-single bond, reversible after reduction of the double bond, is confirmed by X-ray crystal structural analysis.THE isolation and identification of a new naturally occurring compound of the beyerane class1 was recently reported.2 Dissolution of ent-3P-hydroxybeyer-15( 16)-en-Z, 12-dione (Ia)? in acetic acid-acetic anhydride resulted in its ready acetylation to (Ib) : A , , (EtOH throughout) 296 nm ( E 233), r 9-26 (3H, s, 20-H). Addition of either conc. H,SO,, 70% HClO,, or BF,-Et,O to the ice cold solution of either (Ia) or (Ib) induced rearrangement in high yield to the ap-unsaturated ketone (IIa),

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