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Flexible and Convergent Enantioselective Total Synthesis of ()-Juglanaloids A and B: Two Phthalide Spiro Alkaloids with Potential Alzheimer's Disease Inhibitory Activity.
J Org Chem
May 2024
Dipartimento di Chimica e Biologia "A. Zambelli", Università degli Studi di Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Salerno, Italy.
Juglanaloids A and B are recently isolated natural products characterized by an unprecedented spiro bicyclic isobenzofuranone-tetrahydrobenzazepinone framework and a promising antiamyloid activity. Here reported is a straightforward convergent total synthesis of these natural products, which were obtained in high enantiomeric purity (94% and >99% ee for juglanaloids A and B, respectively) through an eight-step longest linear sequence, based on an efficient and reliable enantioselective phase-transfer-catalyzed alkylation step. Considering the interesting biological activity of juglanaloids, this convenient, highly enantioselective, flexible, and predictable synthetic strategy promises to be a powerful tool for accessing potentially bioactive spiro bicyclic phthalide-tetrahydrobenzazepinone derivatives.
View Article and Find Full Text PDFEnantioselective Phase-Transfer-Catalyzed Synthesis of Spirocyclic Azetidine Oxindoles.
Org Lett
March 2024
Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, U.K.
Spiro-3,2'-azetidine oxindoles combine two independently important pharmacophores in an understudied spirocyclic motif that is attractive for medicinal chemistry. Here, the enantioselective synthesis of these structures is achieved in up to 2:98 er through intramolecular C-C bond formation, involving activation of the substrate with a novel SF-containing chiral cation phase-transfer (PT) catalyst. The products are readily elaborated/deprotected to afford medicinally relevant enantioenriched compounds.
View Article and Find Full Text PDFPhase-Transfer-Catalyzed Alkylation of Hydantoins.
ACS Org Inorg Au
August 2022
Department of Chemistry, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
A highly efficient, cost-effective, and environmentally friendly protocol is reported for the C5-selective alkylation of hydantoins under phase-transfer catalysis. The reactions are scalable and only require a catalytic amount of tetrabutylammonium bromide (TBAB) to achieve high yields under mild reaction conditions. Moreover, the method is applicable to a wide range of electrophiles, including alkyl-, allyl-, propargyl-, and benzyl halides, as well as acrylates and dibromoalkanes, but also to virtually any hydantoin precursor.
View Article and Find Full Text PDFPhase-Transfer-Catalyzed Asymmetric Annulations of Alkyl Dihalides with Oxindoles: Unified Access to Chiral Spirocarbocyclic Oxindoles.
Org Lett
January 2022
Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China.
A general phase-transfer-catalyzed asymmetric (+1) ( = 4 or 5) annulation reaction, featuring the direct coupling of simple oxindoles with alkyl dihalides that are allylic/benzylic and non-allylic/benzylic, has been developed to provide previously inaccessible cyclopentane- and cyclohexane-fused spirooxindole scaffolds with high yields and enantioselectivities (88-95% ee). Along with a broad scope and mild conditions, the new protocol also enables a two-step and gram-scale synthesis of the core of the drug ubrogepant.
View Article and Find Full Text PDFPhase-Transfer Catalyzed Asymmetric [4 + 1] Annulations for the Synthesis of Chiral 2,2-Disubstituted Tetrahydrothiophenes.
Org Lett
October 2021
Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China.
An efficient catalytic asymmetric [4 + 1] reaction, which features the use of simple β-keto esters as one-carbon nucleophiles and 5-succinimidothio-pent-2-enoates as four-atom bielectrophiles, has been developed in the presence of a bifunctional chiral phase-transfer catalyst. The new annulation provides a distinct protocol to access the functionalized 2-acyl-2-carboxyl tetrahydrothiophenes bearing consecutive quaternary and tertiary carbon stereocenters in high diastereoselectivities and enantioselectivities. Moreover, the prepared products could be readily transformed into the chiral 2-alkyl-2-carboxyl tetrahydrothiophenes via two steps of debenzoylation and alkylation reactions.
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