35 γ,δ-エポキシアクリル酸エステルを合成ブロックとするポリプロピオネートの新規鎖状立体制御法とその天然物合成への応用(ポスター発表の部)

概要

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A new and potentially useful synthetic method for the polypropionate chains has been developed by using the stereospecific methylation of γ,δ-epoxy acrylates with (CH_3)_3Al. The reaction of (CH_3)_3Al (10 equiv) on trans-γ,δ-epoxy acrylic esters in dichloroethane in the presence of water (6 equiv) at -30℃ gave anti-δ-hydroxy-γ-methylacrylates in a highly stereoselective manner and high yields. On the other hand, cis-γ,δ-epoxy acrylates exclusively produced syn-δ-hydroxy-γ-methylacrylates under the same conditions. In these reactions, addition of water was indispensable. For example, treatment of the epoxyacrylate 1 (optically active) with (CH_3)_3Al gave only the anti compound 2 in 96% yield, while the cis-congeners 3 and 4 produced exclusively the syn-compounds 5 and 6, respectively. The method allows its iterative use. Thus the repeated application of the reaction on the trans-epoxy acrylate 1 gave 27 having four consecutive asymmetric centers in high yield. Synthetic potential of the new method has been demonstrated by the syntheses of (+)-Prelog-Djerassi lactone and (+)-Protomycinolide IV.
天然有機化合物討論会の論文
1991-09-07