16034-99-4Relevant articles and documents
Enantioselective counter-anions in photoredox catalysis: The asymmetric cation radical Diels-Alder reaction
Morse, Peter D.,Nguyen, Tien M.,Cruz, Cole L.,Nicewicz, David A.
, p. 3266 - 3272 (2018)
Control of absolute stereochemistry in radical and ion radical transformations is a major challenge in synthetic chemistry. Herein, we report the design of a photoredox catalyst system comprised of an oxidizing pyrilium salt bearing a chiral N-triflyl pho
Stereodivergent Nucleophilic Additions to Racemic β-Oxo Acid Derivatives: Fast Addition Outcompetes Stereoconvergence in the Archetypal Configurationally Unstable Electrophile
Crawford, Evan T.,De Jesús Cruz, Pedro,Johnson, Jeffrey S.,Liu, Shubin
supporting information, p. 16264 - 16273 (2021/10/21)
Additions of carbon nucleophiles to racemic α-stereogenic β-oxo acid derivatives that deliver enantiomerically enriched tertiary alcohols are valuable, but uncommon. This article describes stereodivergent Cu-catalyzed borylative cyclizations of racemic β-oxo acid derivatives bearing tethered pro-nucleophilic olefins to deliver highly functionalized cyclopentanols containing four contiguous stereogenic centers. The reported protocol is applicable to a range of β-oxo acid derivatives, and the diastereomeric products are readily isolable by typical chromatographic techniques. α-Stereogenic-β-keto esters are typically thought to have extreme or spontaneous configurational fragility, but mechanistic studies for this system reveal an unusual scenario wherein productive catalysis occurs on the same time scale as background substrate racemization and completely outcompetes on-cycle epimerization, even under the basic conditions of the reaction.
Enantioselective Allenoate-Claisen Rearrangement Using Chiral Phosphate Catalysts
Ellwart, Mario,Gensch, Tobias,Han, Seo-Jung,Lin, Hsin-Hui,Miró, Javier,Sigman, Matthew S.,Toste, F. Dean
supporting information, p. 6390 - 6399 (2020/04/27)
Herein we report the first highly enantioselective allenoate-Claisen rearrangement using doubly axially chiral phosphate sodium salts as catalysts. This synthetic method provides access to β-amino acid derivatives with vicinal stereocenters in up to 95percent ee. We also investigated the mechanism of enantioinduction by transition state (TS) computations with DFT as well as statistical modeling of the relationship between selectivity and the molecular features of both the catalyst and substrate. The mutual interactions of charge-separated regions in both the zwitterionic intermediate generated by reaction of an amine to the allenoate and the Na+-salt of the chiral phosphate leads to an orientation of the TS in the catalytic pocket that maximizes favorable noncovalent interactions. Crucial arene-arene interactions at the periphery of the catalyst lead to a differentiation of the TS diastereomers. These interactions were interrogated using DFT calculations and validated through statistical modeling of parameters describing noncovalent interactions.
Biocatalytic dynamic kinetic reductive resolution with ketoreductase from: Klebsiella pneumoniae: The asymmetric synthesis of functionalized tetrahydropyrans
Barik, Rasmita,Halder, Joydev,Nanda, Samik
supporting information, p. 8571 - 8588 (2019/10/02)
Ketoreductase from growing cells of Klebsiella pneumoniae (NBRC 3319) acts as an efficient reagent for converting racemic α-benzyl/cinnamyl substituted-β-ketoesters to the corresponding β-hydroxy esters with excellent yields and stereoselectivities (ee and de >99 %). The reactions described herein followed a biocatalytic dynamic kinetic reductive resolution (DKRR) pathway, which is reported for the first time with such substrates. It was found that the enzyme system can accept substituted mono-aryl rings with different electronic natures. In addition, it also accepts a substituted naphthyl ring and heteroaryl ring in the α-position of the parent β-ketoester. The synthesized enantiopure β-hydroxy esters were then synthetically manipulated to valuable tetrahydropyran building blocks.
