Tricyclic CNS active agents by intramolecular Oxa-Pictet-Spengler reaction

Enantioselective Synthesis of α-Quaternary Isochromanes by Oxidative Aminocatalysis and Gold Catalysis

A novel strategy that combines oxidative aminocatalysis and gold catalysis allows the preparation of chiral α-quaternary isochromanes, a motif that is prevalent in natural products and synthetic bioactive compounds. In the first step, α-branched aldehydes and propargylic alcohols are transformed into α-quaternary ethers with excellent optical purities (>90 % ee) via oxidative umpolung with DDQ and an amino acid-derived primary amine catalyst. Subsequent gold(I)-catalyzed intramolecular hydroarylation affords the isochromane products with retention of the quaternary stereocenter. A second approach explores the use of allylic alcohols as reaction partners for the oxidative coupling to furnish α-quaternary ethers with generally lower enantiopurities. Stereoretentive cyclization to isochromane products is achieved via intramolecular Friedel-Crafts type alkylation with allylic acetates as a reactive handle. A number of synthetic elaborations and a biological study on these α-quaternary isochromanes highlight the potential applicability of the presented method.

Palladium-Catalyzed trans-Hydroalkoxylation: Counterintuitive Use of an Aryl Iodide Additive to Promote C–H Bond Formation

We report an enantioselective palladium-catalyzed trans-hydroalkoxylation of propargylic amines with a trifluoroacetaldehyde-derived tether to build chiral oxazolidines. Diastereoselective hydrogenation using a heterogeneous palladium catalyst then gave access to protected benzylic amino alcohols in 45–87% yields and 84–94% ee values. Hydroalkoxylation of the alkynes required a catalytic amount of aryl iodide, highlighting the counterintuitive key role played by a putative Pd(II)/ArI oxidative addition complex to promote oxypalladation/protodemetalation.

Research progress in biological activities of isochroman derivatives

Isochromans are well recognized heterocyclic compounds in drug discovery which produce diverse therapeutically related applications in pharmacological practices. Medicinal chemistry investigators have synthesized drug-like isochroman candidates with multiple medicinal features including central nervous system (CNS), antioxidant, antimicrobial, antihypertensive, antitumor and anti-inflammatory agents. Simultaneously, SAR (Structure-Activity Relationship) analysis has drawn attentions among medicinal chemists, along with a great deal of derivatives have been derived for potential targets. In this article, we thoroughly summarize the biological activities and part of typical SAR for isochroman derivatives reported on existing literatures and patents, wishing to provide an overall retrospect and prospect on the isochroman analogues.