多置換シクロプロパンの高立体選択的合成と不斉伝搬環拡大反応

抄録

Highly stereoselective synthesis of multi-substituted cyclopropane is important owing to their distribution in nature, and significant biological activities of their analogs. We report here the highly stereoselective synthesis of multi-functionalized cyclopropanes using the SmI₂-promoted Reformatsky-type reaction, acylation, silylation of 1-chlorocyclopropanecarboxylic esters, and the fundamental Reformatsky reaction of 1-bromocyclopropanecarboxylic esters. As the stereo inductive transformation of synthesized highly substituted cyclopropanes, we describe Lewis acid-mediated ring-expansion of methyl (arylhydroxymethyl)-cyclopropanecarboxylates to afford 1,2-dihydronaphthalene-3-carboxylic acid esters. In addition, total syntheses of (+/−)-cyclogalgravin, its dicarboxyl analog, and three kinds of (+)-podophyllic aldehydes have been achieved. Key steps include highly stereoselective constructions of tetra-substituted cyclopropanes and the Lewis acid-mediated chiral transfer ring expansion with excellent level of stereoinductions.