1,3-Dipolar Cycloadditions ofN-Benzyl-2,3-O-isopropylidene-D-glyceraldehyde Nitrone to Methoxyallene – Control of Site- and Diastereoselectivity of Isoxazolidine Formation by Lewis Acids
作者:Branislav Dugovič、Lubor Fišera、Hans-Ulrich Reißig
DOI:10.1002/ejoc.200700724
日期:2008.1
D-glyceraldehyde-derived nitrone 1 and methoxyallene (2) is strongly influenced by Lewis acids. The uncatalyzed reaction results in the formation of isomeric isoxazolidines 3a–3d and 4a–4c, whereas in the presence of different Lewis acids exclusive formation of 4-methylene-substituted isoxazolidines 4a–4d is observed. Furthermore, the diastereofacial selectivity of the methoxyallene addition to nitrone 1 can be controlled
D-甘油醛衍生的硝酮 1 和甲氧基丙二烯 (2) 的环加成的位点选择性受到路易斯酸的强烈影响。未催化的反应导致异构异恶唑烷 3a-3d 和 4a-4c 的形成,而在不同路易斯酸的存在下,观察到仅形成 4-亚甲基取代的异恶唑烷 4a-4d。此外,可以控制甲氧基丙二烯加成到硝酮 1 的非对映选择性,从而产生非对映异构异恶唑烷 3,4'-anti-4 或 3,4'-syn-4,只需使用不同的路易斯酸。使用村桥协议对异恶唑烷 4 进行氧化还原开环产生 α-亚甲基-β-氨基酸酯 5a,b 和 7a,b。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)