EXPERIMENTS DIRECTED TOWARD TOTAL SYNTHESIS OF TERPENES .15. SYNTHESIS OF 3,10-DIMETHOXY-6ABETA,12BBETA-DIMETHYL-5,6,6A,6BALPHA,7,8,12B,13-OCTAHYDROPICENE, A POTENTIAL INTERMEDIATE IN TRITERPENE SYNTHESIS

An approach to the total synthesis of the pentacyclic triterpene alnusenone (1) through the 3-alkoxy-10- hydroxydecahydropicene derivative 4 is outlined, and the initial phases of the scheme were reduced to practice. Three isomers of the 3,10-dimethoxy-6a, 12b-dimethyloctahydropicene 6 (R = CH3) were prepared and characterized. The 6aa, 12bβ-dimethyl derivative 14 resulted from the tricyclic unsaturated ketone 11 in 38-50% overall yield by either of two methods. The two isomeric 6aβ,12bβ-dimethyl derivatives 25 and 26 were prepared from the tricyclic, α,β-unsaturated ketone 15 by an alternate sequence in 24 and 50% overall yields, respectively. In this latter effort it was found necessary to investigate the course of the catalytic hydrogenation of derivatives of the β,γ-unsaturated keto acid 16, and the effect of the substituents present in the C ring on the stereochemical outcome of this reduction was evaluated. © 1969, American Chemical Society. All rights reserved.