49 クレロダン型ジテルペンの合成研究 : 環化反応における多重立体制御を利用したシスクレロダン型ジテルペンの短段階立体特異的合成

概要

論文の詳細を見る
In the continuation of our synthetic study on clerodane diterpenoid we have developed a highly efficient method for the construction of cis-clerodane skeleton where all of its four contiguous chiral centers are built up under complete stereocontrol in a one-pot reaction. The utility of the method has been exemplified by the total syntheses of 15,16-epoxy-cis-cleroda-3,1-triene 19, a constituent of Solidago arguta, and linaridial 25, a biologically active constituent of Linaria japonica Miq. The cyclization of 2-(3,4-dimethyl-6-trimethylsilyl-4-hexenylcyclohexenone 2b with TiCl_4/CH_2Cl_2 at -78℃ was found to proceed under a complete double stereocontrol (orientation and folding strain controls) and, after equlibration of products (NaOMe/MeOH), afforded the trans-decalone derivative 10 as the single diastereomer with the desired configuration. On the basis of this finding we investigated the consummation of clerodan skeleton through the introduction of the substituent at C-4 by the trapping of the intermediary enolate in the cyclization above with C_1-electrophile. The introduction of the angular substituent was attained by the use of MeSCH_2Cl as the trapping reagent to give 14 stereospecifically in 70% yield, which was desulfurized to 15. Starting from 15, total syntheses of 19 (Scheme 5) and linaridial 25 (Scheme 6) have been accomplished by short sequences of reactions.
天然有機化合物討論会の論文
1986-09-09