Primary and Secondary Allyltitanium(IV) Reagents in Aldehyde Allylation II: Application to an Enantioselective Preparation of a C1-C7 Fragment of Spiramycin
作者:Janick Ardisson、Patrick Razon、Marie-Ange N’Zoutani、Sylvie Dhulut、Sophie Bezzenine-Lafollée、Ange Pancrazi
DOI:10.1055/s-2004-834913
日期:——
A synthetic approach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe aldehyde allylation. This reaction was carried outbetween an optically pure aldehyde 32 and a (′)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions
描述了一种重要的抗生素化合物螺旋霉素东部的合成方法。首先设想通过 Hoppe 醛烯丙基化引入侧链。该反应在光学纯醛32和衍生自伯γ-烷氧基烯丙基(二异丙基)氨基甲酸酯的(')-γ-烷氧基烯丙基钛(IV)物质之间进行。在动力学拆分条件下,以 81% 的产率获得抗 Cram 化合物 35 与 Cram 异构体 34 的 80:20 混合物。使用光学纯的 (S)-γ-烷氧基烯丙基(二异丙基)氨基甲酸酯 36,在 n-BuLi.TMEDA/Ti(Oi- Pr) 4 条件,其与醛 32 在双立体分化中反应以 80% 的产率 (95% de) 提供预期的 Cram 化合物 40。