24 ノピノン骨格の特徴を利用した天然物合成の展開(ポスター発表の部)

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We have been studying natural product synthesis starting with (+)-nopinone (1) as a chiral source. In this presentation, we report our recent synthetic study. (a) A general and convenient synthetic route to 4,4-dialkyl nopinones 16a-d from phenylthio enone 9 derived from 1 was developed using repetition of the two-step sequence of reactions, Pummerer rearrangement and Michael reaction, as the key steps followed by reductive desulfurization of the resulting sulfone 15a-d. (b) BF_3 OEt_2-promoted cleavage of cyclobutane ring in 16 provided enol acetates 17 with little loss of optical integrity. (c) Chemical transformation starting from compounds possessing nopinone skeleton, 25a and 33, as well as cyclobutane opened compounds, 26a and 27b, was carried out, giving chiral building blocks, 29a, 30a, 31, 37, and 38, suitable for natural product synthesis. (d) Alkylation of phenylsufonyl enone 6 with a variety of alkyl halides under the conditions of K_2CO_3 in MeCN proceeded at the γ position to the conjugated enone system in regio- and dia-stereoselective mode to give 44a-d in good yields. (e) Starting with 44a, the first and highly stereoselective total synthesis of a nardosinan sesquiterpene, (-)-kanshon A (8) was accomplished.
天然有機化合物討論会の論文
1991-09-07