マイトトキシンの完全構造決定

Abstract

Maitotoxin (MTX, 1) is the most toxic and largest non-biopolymer known to date. The complete structural determination of MTX including the absolute configuration has been achieved recently. The relative configurations of the four acyclic portions (C1-C15, C35-C39, C63-C68, and C134-C142) were elucidated by (1) the extensive configurational analysis mainly using long-range carbon-proton coupling constants (2, 3JC, H), and (2) the stereoselective synthesis of the eight model compounds (2A-2D, 13, 27A, 27B, and 47) which were furnished with thus assigned relative configurations. The comparison of their 1H and 13C-NMR data with those for the corresponding portion of MTX evidently established the relative configuration from C1 to C138. The absolute configuration of the entire molecule was determined by the enantioselective synthesis and chiral gas chromatographic comparison with a degradated fragment (3, 4-dimethy1-6-hepten-1-o1) derived from the natural product, which involved two chiral centers at C138 and C139.The present results have revealed that the preferred conformation of an appropriately designed model compound with the correct configuration closely mimics that of the corresponding portion of MTX. Thus, we could deduce the overall conformation of MTX by assembling the preferred conformation of each model compound based on the NMR data.