8 1,3-ポリオールの立体選択的合成(口頭発表の部)  [in Japanese] 8 Stereodivergent Synthesis of 1,3-Polyols  [in Japanese]

In connection with the stereochemical studies of sporaviridin, a polyol macrolide antibiotic, we have developed a convergent general protocol for syn-1,3-polyol synthesis. The method is extendable to higher homologs of this series by repetition. Using this new method, total synthesis of 4,6,8,10,12,14,16,18,20-nonamethoxy-1-pentacosene (3), isolated from blue-green alga Tolypothrix conglutinate var. chlorata, has been accomplished in 21 steps from the ketone (7). Second, a new method for the preparation of anti-1,3-polyol has been developed using a chiral building block (6), a chiral epoxide (22), and LiAlH(O'Bu)_3-LiI reduction. The LiAlH(O'Bu)_3-LiI reduction is a useful method for preparing 1,3-anti-3,5-syn-triol units from B-alkoxy-B-hydroxy ketones with anti-relationship of the alkoxy and the hydroxy groups. The selectivity of the rduction is anti:syn=95:5. Finally, combination of the syn- and anti-1,3-polyol syntheses culminated in establishing a new stereodivergent synthesis of 1,3-polyols containing syn- and anti-1,3-diol units in the chain and four diasteroisomeric polyols (43), (44), (45), and (46) were synthesized in a stereocontrolled manner. Since the present technology could provide facile access to 1,3-polyols by the combination of chiral epoxides, enantiomeric dithianes of (6), and reducing agents of LiAlH_4-LiI and LiAlH(O'Bu)_3-LiI, the flexibility of the reaction sequence in preparing any desired stereo-chemical combination is considerably enhanced.