Peptide-Catalyzed Conversion of Racemic Oxazol-5(4H)-ones into Enantiomerically Enriched α-Amino Acid Derivatives
摘要:
We report the development and optimization of a tetrapeptide that catalyzes the methanolytic dynamic kinetic resolution of oxazol-5(4H)-ones (azlactones) with high levels of enantioinduction. Oxazolones possessing benzylic-type substituents were found to perform better than others, providing methyl ester products in 88:12 to 98:2 er. The mechanism of this peptide-catalyzed process was investigated through truncation studies and competition experiments. High-field NOESY analysis was performed to elucidate the solution-phase structure of the peptide, and we present a plausible model for catalysis.
Synthesis of fluorinated α-amino ketones. Part II: α-acylaminoalkyl α′, α′-difluoroalkyl ketones
作者:Michael Kolb、Bernhard Neises
DOI:10.1016/s0040-4039(00)84972-2
日期:1986.1
The synthesis of α-acylaminoalkyl 1.1-difluoro-3-butenyl ketones is described. Reaction of substituted 5(4H)-oxazolones , obtained fromα-amino acids, with 2.2-difluoro-4-pentenoic acid anhydride (for R2 = C6H5) or with 2.2-difluoro-4-pentenoic acid chloride and 4-dimethylaminopyridine / triethylamine [for R2 = CH3, C6H5, CH(CH2C6H5)NHCO2CH2C6H5] followed by treatment with anhydrous oxalic acid gives
描述了α-酰基氨基烷基1.1-二氟-3-丁烯基酮的合成。由α-氨基酸获得的取代的5(4H)-恶唑酮与2.2-二氟-4-戊烯酸酐(对于R 2 = C 6 H 5)或2.2-二氟-4-戊烯酰氯和4 -二甲基氨基吡啶/三乙胺[对于R 2 = CH 3,C 6 H 5,CH(CH 2 C 6 H 5)NHCO 2 CH 2 C 6 H 5而言],然后用无水草酸处理,得到目标结构。
Enantioselective organocatalytic syntheses of α-selenated α- and β-amino acid derivatives
amino acids are valuable targets but methods for the stereoselective α-selenation of simple amino acid precursors are rare. We herein report the enantioselective electrophilic α-selenation of azlactones (masked α-amino acidderivatives) and isoxazolidin-5-ones (masked β-amino acids) using Cinchona alkaloids as easily accessible organocatalysts. A variety of differently substituted derivatives was accessed
Dynamic Kinetic Resolution of Azlactones by Bifunctional Thioureas with α‑Trifluoromethyl or Methyl Groups
作者:Marcos Hernández-Rodríguez、Eddy I. Jiménez、Margarita Cantú-Reyes、Miguel Flores-Ramos、Carlos A. Román-Chavarría、Howard Díaz-Salazar
DOI:10.1055/a-1892-9911
日期:2022.10
The asymmetric ring opening of azlactones via dynamickineticresolution (DKR) is investigated by contrasting thioureas incorporating 1-arylethyl substituents against their more acidic trifluoromethylated analogs. All the catalysts under study outperform Takemoto’s thiourea because of the inclusion of an additional chiral center. However, the difference in yield and selectivity between the fluorinated
Construction of α,β-Diamino Diacid Derivatives with Adjacent Acyclic Tetrasubstituted Stereocenters
作者:Feng Zhou、Qi-Long Hu、Ke-Qiang Hou、Albert S. C. Chan、Xiao-Feng Xiong
DOI:10.1021/acs.joc.2c00950
日期:2022.7.1
A convenient strategy for the diastereoselective synthesis of α,β-diamino diacid derivatives bearing congested vicinal acyclic tetrasubstituted stereocenters via catalytic Mannich-type reactions of azlactones and 2-aminoacrylates was established. A diverse set of α,β-diamino diacid derivatives were synthesized in good to excellent yields and diastereoselectivities. Good enantioselectivity (up to 98:2
Organocatalytic Asymmetric [4 + 2] Cyclization of Azadienes with Azlactones: Access to Chiral 3-Amino-δ-Lactams Derivatives
作者:Wu-Jingyun Zhou、Xiaoning Yu、Chen Chen、Wei Lan、Gu Zhan、Jin Zhou、Qian Liu、Wei Huang、Qian-Qian Yang
DOI:10.1021/acs.joc.3c00663
日期:2023.10.6
a series of chiral δ-lactam frameworks have been synthesized and catalyzed by chiral phosphoric acid (CPA) utilizing two kinds of open-chain aza-dienes and azlactones derived from amino acids. This powerful [4 + 2] annulation produces a broad substrate scope with functional group tolerance in yield up to 97% with up to 98:2 er. Moreover, a facile scale-up and straightforward conversion to diversely