Chemistry of the Podocarpaceae. LXXII. Ring-C Modifications of Totarol

Abstract

Totarol (1) has been converted into conjugated dienolides which have the B/C-ring systems found in naturally occurring nagilactones A and C and their analogues. Thus, treatment of the epoxide (11) with titanium(IV) tetrachloride affords the desired 7,9(11)- diene (12) and the saturated γ- lactone (23). Treatment of the epoxide (11) with diazabicyclo [3.4.0]non-5-ene gives a high yield of the butenolide (24); the alcohol (25) has been shown to be an intermediate in this reaction. Treatment of (11) with lithium iodide dihydrate in collidine gives the butenolides (24) and (26), and the novel rearrangement product (27) which is slowly converted on standing into the epoxide (29). Treatment of (11) with anhydrous lithium iodide gives the α- pyrone (30). The structures of compounds (11), (23), (24) and (29) have been determined by single-crystal X-ray diffraction measurements.