12 A環置換天然ジテルペノイドの合成

概要

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In our studies on chemical conversion of pine tree (main component, l-abietic acid (1)) to biogenetically active compounds, the substitution to A-ring is regarded as one of the basic problems. An investigation of benzonilidene compound (2) derived from (1), gave a clue for the solution. Under an acidic condition (Ac_2-H_2SO_4), (2) underwent rearrangement to enol acetate (4) accompanied with migration of C-10 methyl group to the C-5 position. Treatment (conc. H_2SO_4) of (4) and its hydrolized compound (5) easily gave the original compound (2). In the rearrangement, the electrophilic reagent is used instead of the proton, selective substitution at C-1 should proceed. In fact, the two reactions (Ac_2O- and NBS-BF_3.Et_2O) of (2) and (5) succeed to give the compounds having substituted A-ring (17) and (24), respectively. Especially, the latter (24) is a potential intermediate for the above purpose. As an example of the synthesis, natural diterpene, teideadiol (3) was accomplished to synthesize from (24). Also, (24) was converted to (40), which is considered to be suitable for the synthesis of salviol (41) and hinokione (42).
天然有機化合物討論会の論文
1973-10-01