Synthetic studies on the construction of the fundamental skeleton of erythroxydiol X. Syntheses of 3a,10a-dimethyl-(3aβ,4aα,6aβ,10aα,10bβ)-perhydrocyclopropa[j]phenanthrene-5,8-dione and 8α-benzoyloxy-3a,10a-dimethyl-(3aβ,4aα,6aβ,10aα,10bβ)-perhydrocyclopropa[j]phenanthren-3-one

Abstract

Experiments on the synthesis of the fundamental skeleton (2) of erythroxydiol X (1), a new rosane-type diterpene from Erythroxylon monogynum are described. The cyclopropyl ketones (6) and (9) were synthesised from the tricyclic oxo-acid (3a) and the monomethylated αβ-unsaturated ketone (7), respectively. Contrary to our expectation, reduction of either compound (6) or (9) with lithium aluminium hydride in dioxan did not give the desired compound (2), but the seven-membered ring compound (16), presumably by hydrogenolytic cleavage of the cyclopropane ring.