5 分子内Diels-Alder反応をKey ReactionとするQuassinoidsの合成研究

概要

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Synthetic studies on a carbon framework of quassinoid klaineanone (1) and quassinoidal antileukemia agent bruceantin (2) have been carried out. The key step in this approach was an stereoselective intramolecular cycloaddition of the o-quinodimethanes (4), (27), generated in situ from the thermolysis of the benzocyclobutenes (18 and 34). The compound (18) was prepared from norcamphor via stereoselective methylation of the lactone (7). The cycloadduct (20) was converted into the tetracyclic lactone (22) whose structure was confirmed by X-ray analysis. The C-8 methyl analog (24) which is a klaineanone model compound was also synthesized. The compound (27) was prepared using a methoxyallene cyclization reaction. Stereoselective introduction of C-2 unit into the cycloadducts (39 and 47) was eventually achieved in high overall yield by a two step procedure: (i) Horner-Emmons reaction; (ii) NaHTe reduction. The construction of D-ring of the pentacyclic bruceantin model compound (25) is under way.
天然有機化合物討論会の論文
1982-09-10