作者:Deepak M. Shendage、Roland Fröhlich、Klaus Bergander、Günter Haufe
DOI:10.1002/ejoc.200400665
日期:2005.2
α-methyl derivative 1b with 2-fluoroallyl tosylate, subsequent mild acidic deprotection of the products 2a and 2b, and basic hydrolysis of the thus formed N-methylamides 4a and 4b gave (S)-2-amino-4-fluoropent-4-enoic acid (5a) and (S)-2-amino-4-fluoro-2-methylpent-4-enoic acid (5b). Basic hydrolysis of compound 4a was accompanied by partial racemization, which was overcome by applying a new stereoconservative
(S)-Boc-BMI(1a,BMI = 2-tert-butyl-3-methylimidazolidin-4-one)及其α-甲基衍生物1b与2-氟代烯丙基甲苯磺酸酯的不对称烷基化,随后产物2a的温和酸性脱保护和2b,由此形成的N-甲基酰胺4a和4b的碱水解得到(S)-2-氨基-4-氟戊-4-烯酸(5a)和(S)-2-氨基-4-氟-2 -甲基戊-4-烯酸(5b)。化合物 4a 的碱性水解伴随着部分外消旋化,这通过应用新的立体保守脱酰胺程序来克服。在动力学控制下形成的烷基化顺式构型产物 2a 在与 2 n NaOH 回流时差向异构化,得到热力学更稳定的反式异构体 9。 (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)