29 オキシラニルアニオンを用いる環状ポリエーテルの合成(口頭発表の部)

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One of the most characteristic and interesting classes of marine toxins produced by dinoflagellates is the polycyclic ethers. Trans-fused tetrahydropyran rings are the most frequently encountered cyclic units and form a rigid backbom of this class of toxins. We have developed a novel reiterative route to trans-fused tetrahydropyran ring systems. The key features of the synthesis are alkylation of an oxiranyl anion stabilized by a sulfonyl group and a 6-endo mode of cyclization. The approach involves the following five-step process: (i) transformation of a monocyclic diol to a silyl-protected triflate by a one-pot procedure (14→4), (ii) coupling reaction of the triflate with the oxiranyl anion generated from an epoxy sulfone by deprotonation (4→15), (iii) stereo- and regioselective 6-endo mode of cyclization of the coupling product to a bicyclic ketone (15→16), (iv) stereoselective reduction of the ketone (16→17), and (v) deprotection (17→18). The resulting bicyclic compound contains useful functional group that can be explored for further elaboration of the system. Reiteration of the sequence provide predictable access to tri- and polytetrahydropyran ring systems. Application of the present method to prepare a tetrahydrofuran ring by 5-endo cyclization was demonstrated by the synthesis of (6S,7S,9R,10R)-6,9-epoxynonadec-18-ene-7,10-diol (35) isolated from the brown alga Notheia anomala.
天然有機化合物討論会の論文
1996-09-02