The hetero Michael-addition of (S)-(-)2-methoxymethyl-1-trimethylsilylaminopyrrolidine (TMS-SAMP) to α,β-unsaturated esters 1, followed by α-alkylation of the intermediate esterenolates with various electrophiles yields α-substituted β-hydrazino esters 3 of anti-configuration in good to excellent diastereomeric excesses (de = 63- ≥96 %). Subsequent reductive N-N bond cleavage leads to β-amino acid esters 4 (R1 = C6H11) in good yields and high diastereo and enantiomeric purity (de,ee ≥96 %). The stereochemistry was confirmed by NMR spectrocopy and X-ray structure analysis.
将(S)-(-)2-甲氧基甲基-1-三甲基
硅烷基
氨基
吡咯烷(TMS-
SAMP)与δ,δ-不饱和酯 1 进行杂化迈克尔加成,然后用各种亲电体对中间酯进行δ-烷基化反应,可得到非对映过量(de = 63- ≥96%)的反构型δ,δ-取代
肼酯 3。随后进行还原性 N-N 键裂解可得到δ-
氨基酸酯 4(R1 =
C6H11),产量高,非对映和对映纯度高(de,ee ≥96%)。核磁共振光谱和 X 射线结构分析证实了其立体
化学性质。