29 グリシノエクレピンAおよびBの不斉全合成(口頭発表の部)

概要

論文の詳細を見る
Glycinoeclepin A (1) and B (2) were isolated from dried roots of the kidney bean in 1982 as a hatch-stimulating agent of the soybean cyst nematode. Toward the total synthesis of 1 and 2, we designed a synthetic strategy based on the cyclopentene annulation method and an alkylation reaction using a bridgehead anion species. Stereoselective construction of the CD ring system was achieved through a conjugate addition reaction of optically active enone 9 with an anion species generated from nitrile 10 followed by a cyclization reaction promoted by acetic acid. After elongation of the side chain via a stereoselective hydroboration reaction followed by the Suzuki-Miyaura coupling, the configuration of the C12 hydroxyl group was inverted through stereoselective reduction of ketone 16 by using LiEt_3BH in toluene. Introduction of the A ring moiety was accomplished by the alkylation reaction of tosylate 5 with a bridgehead anion species generated from dimethylhydrazone derivative 26. Hydrolysis of 26 afforded the corresponding ketone, which was subjected to palladium-catalyzed carbonylation followed by selective oxidative cleavage of the terminal double bond to give aldehyde 3. Finally, Pinnick oxidation and subsequent hydrolysis of the ester groups provided Glycinoeclepin A (1). Glycinoeclepin B (2) was also synthesized from the common intermediate 3 by using the asymmetric Nozaki-Hiyama-Kishi coupling. Thus, Ni(II)/Cr(II)-mediated coupling reaction of aldehyde 3 and β-iodo-α,β-unsaturated ester in the presence of optically active sulfonamide 29 afforded adduct 30 as a major isomer. Although the dicarboxylic acid derived from 30 was not identical with Glycinoeclepin B, the corresponding C23-epimer 32 was converted to the natural product. These results suggested that the configuration of the C23 hydroxyl group would be β, which was further confirmed by using the modified Mosher's method.
2008-09-01

29 グリシノエクレピンAおよびBの不斉全合成(口頭発表の部)

スポンサーリンク

概要

著者

関連論文

スポンサーリンク