Enantiodifferentiating functionalization of 2-substituted 1,3-propanediols via chiral spiroketal: Two methods for the preparation of (S)-2,3-dimethylbutyl phenyl sulfides
Asymmetric Desymmetrization of 2-Substituted 1,3-Propanediols by Using Oxazaborolidinone-Mediated Enantioselective Ring-Cleavage of Prochiral Acetal Derivatives
作者:Toshiro Harada、Keiko Imai、Akira Oku
DOI:10.1055/s-2002-31928
日期:——
Nonenzymatic desymmetrization of 2-substituted 1,3-propanediols leading to the enantiomerically enriched 3-benzyloxy-1-propanols was achieved by using oxazaborolidinone-mediated enantioselective ring-cleavage reaction of the dioxane acetal derivatives.
Enantioselective Desymmetrization of 2-Aryl-1,3-propanediols by Direct <i>O</i>-Alkylation with a Rationally Designed Chiral Hemiboronic Acid Catalyst That Mitigates Substrate Conformational Poisoning
作者:Carl D. Estrada、Hwee Ting Ang、Kim-Marie Vetter、Ashley A. Ponich、Dennis G. Hall
DOI:10.1021/jacs.1c00759
日期:2021.3.24
operationally simple, ambient conditions. Nucleophilic activation and discrimination of the enantiotopic hydroxy groups on the diol substrate occurs via a defined chairlike six-membered anionic complex with the hemiboronic heterocycle. The optimal binaphthyl-based catalyst 1g features a large aryloxytrityl group to effectively shield one of the two prochiral hydroxy groups on the diol complex, whereas
Asymmetric Desymmetrization of 2-Substituted 1,3-Propanediols via Catalytic Enantioselective Ring-Cleavage Reaction of Cyclic Acetal Derivatives
作者:Toshiro Harada、Koudai Shiraishi
DOI:10.1055/s-2005-871937
日期:——
Non-enzymatic desymmetrization of 2-substituted 1,3propanediols leading to the enantiomerically enriched 3-benzyloxy-1-propanols was achieved by using oxazaborolidinone-catalyzed enantioselective ring-cleavage reaction ofthe cyclic acetal derivatives with dimethylsilyl ketene S,O-acetal as a key reaction.
Enantiodifferentiating Functionalization of Prochiral Diols by Highly Stereoselective Ring-Cleavage Reaction of Spiroacetals Derived from<i>I</i>-Menthone with Allyltrimethylsilane-Titanium Tetrachloride
Enantiodifferentiating transformation of prochiral diols possessing σ-symmetry was realized by the utilization of titanium tetrachloride-promoted selective ring-cleavage reaction of spiroacetals derived from the diols and I-menthone with allyltrimethylsilane.
SN2'-Reactions of Peptide Aziridines. A Cuprate-Based Approach to (E)-Alkene Isosteres
作者:Peter Wipf、Paul C. Fritch
DOI:10.1021/jo00096a033
日期:1994.8
Alkenylaziridines were prepared from allylic alcohols via Sharpless epoxidation; oxirane to aziridine conversion under modified Staudinger conditions, and Wittig chain extension. Alternatively, beta-hydroxy alpha-amino acids such as threonine can serve as readily available precursors. The corresponding N-acyl, -peptidyl-, -carbamoyl-, and -sulfonylaziridines underwent a high-yielding anti-S(N)2' alkylation with organocopper/BF3 complex to give (E)-alkene peptide isosteres in 62 to >98% de. The stereoselectivity of the addition process was studied by H-1 and F-19 NMR as well as chemical degradation. Alkene isosteres are important nonhydrolyzable and rigidified analogs of peptide bonds in biologically active peptides. This new methodology considerably facilitates the synthesis and the study of these peptide mimetics, since alkenylaziridines are readily prepared and side-chain modification is simplified by the wide range of functionalized organocopper reagents that are available.