【摘要】 本文报道以L-缬氨酸为手征性助剂,DL-丙氨酸为原料,（3S,6SR）-2,5-二甲氧基-3-异丙基-6-甲基-3,6-二氢吡嗪（1）为杂环中间体,（2R,3SB）-O-甲基-a-甲基丝氨酸甲酯衍生物的对映选择合成。在丁基锂作用下,化合物1转变成锂衍生物（2）,它与醛类化合物（3）作用可得具有很高立体选择性的羰基加成物（4）。羰基化合物以C-3位异丙基的反式进入1的C-6位,即在C-6位引入（R）-构型。为避免4水解时的反醛醇缩合反应,必须对其羟基加以保护,然后才能经水解合成O-甲基-a-甲基丝氨酸衍生物（6）。用加入手征性位移试剂Eu（hfc）₃的¹H NMR谱测定了对映体过量百分数。更多还原

【Abstract】 Enantioselective synthesis of （2R. 3SR）-O-methyl-α-methyl-serine methyl ester derivatives via heterocyclic intermediates-（3S, 6SR）-2, 5-dimethoxy-3-isopropyl-6-methyl-3, 6-dihydropyrazine （1）-using L-valine as chiral auxiliary reagent and DL-alanine as starting material has been studied. The compound 1 is converted with butyl-lithium into its lithium derivative （2） which on reaction with aldehydes （3） affords the carbonyl adduct （4） with extremely high diastereoselectivity. In this reaction the carbonyl compound enters trans to the isopropyl group at C-3, i. e. the （R）-configuration is induced at C-6. Owing to occurrence of retroaldol reaction during the hydrolysis, so the hydroxy group of 4 must be protected. Then α-methyl serine methyl esters （6） can be obtained after hydrolysis. Enantiomeric excess is determined by ¹H NMR spectral analysis using Eu（hfo）₃ as chiral shift reagent.更多还原