Memory of Chirality in theEnantioselective Synthesis of β-Lactams Derived from AminoAcids. Influence of the Reaction Conditions
作者:Rosario González-Muñiz、Mª Angeles Bonache、Guillermo Gerona-Navarro、Mercedes Martín-Martínez、Mª Teresa García-López、Pilar López、Carlos Cativiela
DOI:10.1055/s-2003-39301
日期:——
The asymmetric induction observed during cyclisation of N-benzyl-N-chloroacetyl-l-Phe derivatives to the corresponding S-enriched 2-azetidinones, ascribed to chirality memory, can be controlled by the appropriate choice of the base and solvent. Using the organic base BTPP, the ee values obtained in different solvents showed a good correlation with the AN solvent parameter, except for NMP. It seems that a combination of the solvent properties, rather than individual parameters, and the presence of enolate aggregates are decisive for final enantiomer distribution.
在将 N-苄基-N-氯乙酰基-l-Phe 衍生物环化成相应的 S-富集 2-氮杂环丁酮的过程中观察到的不对称诱导归因于手性记忆,可以通过适当选择碱和溶剂来控制。使用有机碱 BTPP,除 NMP 外,在不同溶剂中获得的 ee 值与 AN 溶剂参数有很好的相关性。由此看来,对映体的最终分布起决定性作用的是溶剂特性(而不是单个参数)和对映体聚集体的存在。
Entry to New Conformationally Constrained Amino Acids. First Synthesis of 3-Unsubstituted 4-Alkyl-4-carboxy-2-azetidinone Derivatives via an Intramolecular <i>N</i><sup>α</sup><i>-C</i><sup>α</sup>-Cyclization Strategy
作者:Guillermo Gerona-Navarro、Maria Angeles Bonache、Rosario Herranz、Maria Teresa García-López、Rosario González-Muñiz
DOI:10.1021/jo015559b
日期:2001.5.1
N-benzyl-N-chloroacetyl aminoacidderivatives is described. This study resulted in the first concise and versatile route to the preparation of 3-unsubstituted 4-alkyl-4-carboxy-2-azetidinones, to be included into the scarce family of beta-lactams with quaternary centers at the C(4) position. Particularly noteworthy is that the intramolecular N(alpha)-C(alpha)-cyclization of Phe and Leu derivatives afforded the