A new chiral glycine synthon. Synthesis, x-ray structure of (−).(2S,4R)-2-ethoxycarbonyl-4-phenyl-1,3-oxazolidine and diastereoselective nucleophilic ring opening to (R)-ethyl α-amino carboxylates.
作者:Celia Andrés、Alfonso González、Rafael Pedrosa、Alfonso Pérez-Encabo、Santiago García-Granda、M.A. Salvadó、Fermín Gómez-Beltrán
DOI:10.1016/s0040-4039(00)61274-1
日期:1992.8
Condensation of (R)-N-benzyl-2-phenylglycinol 1 with the methyl hemiacetal of ethyl glyoxylate leads to (2S,4R)-2-ethoxycarbonyl-4-phenyl-1,3-oxazolidine 2 as the major product, obtained as a pure enantiomer after column chromatography. Compound 2 is stereoselectively cleaved by dialkylzinc reagents, prepared from alkylmagnesium iodides and ZnCl2, with moderate to good d.e.ś (72–94 %). These compounds
(R)-N-苄基-2-苯基甘氨醇的缩合1与乙醛酸乙酯引线的甲基半缩醛向(2S,4R)-2-乙氧羰基-4-苯基-1,3-恶唑烷2所获得作为主要产物,柱层析后得到纯对映体。化合物2被二烷基锌试剂立体选择性切割,该试剂由碘化烷基镁和ZnCl 2制备,中等至良好(72-94%)。这些化合物经柱色谱分离并在碳上含10%Pd的条件下通过氢解脱苄基作用后,得到对映体纯的α-氨基羧酸乙酯,具有良好的化学收率。