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A novel synthesis of natural drimanic compounds, (-)-albrassitriol (2) and (-)-6-epi-albrassitriol (3), has been carried out starting from an easily available labdane diterpenoid, (+)-larixol (1). In a two-step procedure, (+)-larixol (1) was converted into 14,15-bisnorlab-7-ene-6,13-dione (9), which was then submitted to a Norrish type II photochemical degradation yielding drim-7,9(11)-diene-6-one (10), whose treatment with OsO4 led selectively to the formation of drim-7-ene-9α,11-diol-6-one (12). The same compound was obtained by selective epoxidation of the C(9)-C(11) double bond in drim-7,9(11)-diene-6-one (10) with monoperphtalic acid. Treatment of the resulting mixture of α- and β-epoxides (13 and 14) with HClO4 yielded drim-7-ene-9α,11-diol-6-one (12). Reduction of the C6-carbonyl group in drim-7-ene-9α,11-diol-6-one (12) with LiAlH4 afforded (-)-albrassitriol (2) and (-)-6-epi-albrassitriol (3), 12.4% and 13.6% overall yields, respectively.

The paper describes a new pathway for an efficient synthesis of natural and bioactive drimanic compounds ( - )-pereniporin B (1) and ( - )-cinnamosmolide (2) from ketodiol 7, an intermediate obtained before from accessible labdane diterpenoid (+)-larixol (3). The key step involves allylic bromination of acetate 8 with N-bromosuccinimide. The in vitro antimicrobial and antifungal activities of all compounds are also reported. Their structures were confirmed by both spectroscopic data and chemical transformations.