Direct anti-selective catalytic asymmetric Mannich-type reactions of alpha-ketoanilides for the synthesis of gamma-amino amides and azetidine-2-amides

De Novo Synthesis of α-Ketoamides via Pd/TBD Synergistic Catalysis

Precisely controlling the product selectivity of a reaction is an important objective in organic synthesis. α-Ketoamides are vital intermediates in chemical transformations and privileged motifs in numerous drugs, natural products, and biologically active molecules. The selective synthesis of α-ketoamides from feedstock chemicals in a safe and operationally simple manner under mild conditions is a long-standing catalysis challenge. Herein, an unprecedented TBD-switched Pd-catalyzed double isocyanide insertion reaction for assembling ketoamides in aqueous DMSO from (hetero)aryl halides and pseudohalides under mild conditions is reported. The effectiveness and utility of this protocol are demonstrated by its diverse substrate scope (93 examples), the ability to late-stage modify pharmaceuticals, scalability to large-scale synthesis, and the synthesis of pharmaceutically active molecules. Mechanistic studies indicate that TBD is a key ligand that modulates the Pd-catalyzed double isocyanide insertion process, thereby selectively providing the desired α-ketoamides in a unique manner. In addition, the imidoylpalladium(II) complex and α-ketoimine amide are successfully isolated and determined by X-ray analysis, confirming that they are probable intermediates in the catalytic pathway.

Ru(II)-catalyzed oxidative coupling of sulfoxonium ylides with amines: efficient synthesis of α-ketoamides and indolo[2,1-a]isoquinolines

The first use of sulfoxonium ylides for the synthesis of α-ketoamides is described via a Ru(II)-catalyzed amidation reaction with amines. The same Ru(II)-catalyzed reaction of sulfoxonium ylides with 2-phenylindoles provided indolo[2,1-a]isoquinolines instead of α-ketoamides.

Copper-Catalyzed Substrate-Controlled Carbonylative Synthesis of α-Keto Amides and Amides from Alkyl Halides

Controllable production of α-keto amides and amides from the same substrates is an attractive goal in the field of transition-metal-catalyzed (double-)carbonylation. Herein, a novel copper-catalyzed highly selective double carbonylation of alkyl bromides has been developed. Moderate to good yields of α-keto amides were obtained as the only products. In the case of alkyl iodides, double- and mono-carbonylation can be achieved controllably under different conditions.

Diversification of α-ketoamides via transamidation reactions with alkyl and benzyl amines at room temperature

A wide range of N-tosyl α-ketoamides underwent transamidation with various alkyl amines in the absence of a catalyst, base, or additive. On the other hand, transamidation in N-Boc α-ketoamides was achieved in the presence of Cs₂CO₃. The reactions proceeded at room temperature and provided good to excellent yields of transamidation products under the optimized conditions. Broad substrate scope, functional group tolerance and quick conversions are the important features of the developed methodology.

The Alpha Keto Amide Moiety as a Privileged Motif in Medicinal Chemistry: Current Insights and Emerging Opportunities

Over the years, researchers in drug discovery have taken advantage of the use of privileged structures to design innovative hit/lead molecules. The α-ketoamide motif is found in many natural products, and it has been widely exploited by medicinal chemists to develop compounds tailored to a vast range of biological targets, thus presenting clinical potential for a plethora of pathological conditions. The purpose of this perspective is to provide insights into the versatility of this chemical moiety as a privileged structure in drug discovery. After a brief analysis of its physical-chemical features and synthetic procedures to obtain it, α-ketoamide-based classes of compounds are reported according to the application of this motif as either a nonreactive or reactive moiety. The goal is to highlight those aspects that may be useful to understanding the perspectives of employing the α-ketoamide moiety in the rational design of compounds able to interact with a specific target.

Chemical Studies on Bioactive Natural Products Directed toward Development of Novel Antiinfective and Anticancer Medicines

Natural products are still rich sources of clinically used medicines and lead compounds for them. This review summarizes chemical studies carried out by the author on natural products of microorganism origin, many of which were discovered at the Institute of Microbial Chemistry (BIKAKEN). Caprazamycin B is a liponucleoside antibiotic from which CPZEN-45, an antituberculosis agent with a unique mode of action, was developed. Intervenolin and leucinostatin A exert antiproliferative activity toward tumor cells in the presence of the corresponding stromal cells, which implies that the primary molecular targets of these molecules should be related to growth signals from normal (stromal) cells. Details of the endeavors to establish efficient synthetic routes to these compounds which accelerated structure-activity relationship studies and further evaluation of biological activity are described.

Recent developments in functionalization of acyclic α-keto amides

This review describes the synthetic utility of α-keto amides to synthesize various important molecules via mono, dual and triple functionalization reactions.

Metal-free, direct conversion of α-amino acids into α-keto γ-amino esters for the synthesis of α,γ-peptides

An efficient, metal-free synthesis of unusual α-keto γ-amino esters from α-amino acids is achieved by a radical scission–oxidation–addition of silyloxy acrylates procedure, where no purification of the reaction intermediates is needed. The process allows the synthesis of α,γ-peptides.

A novel homobimetallic nickel complex for the asymmetric direct Mannich reaction of imines: a practical method on a multi-gram scale

A practical asymmetric direct Mannich reaction catalyzed by a homobimetallic nickel complex with a low catalyst loading on a preparative scale.

Reactions of pyruvates: organocatalytic synthesis of functionalized dihydropyrans in one pot and further transformations to functionalized carbocycles and heterocycles

Concise cascade reactions of pyruvates with aldehydes that generate functionalized dihydropyran derivatives in one pot have been developed. The products, dihydropyrans, were further concisely transformed to various functionalized molecules.

Asymmetric transformations involving 1,2-dicarbonyl compounds as pronucleophiles

This article concentrates on the versatile nucleophilic reactivity of 1,2-dicarbonyl compounds in various asymmetric transformations. Although underexploited in comparison to their 1,3-dicarbonyl homologues, the presence of adjacent multiple reactive centres allows the selection of specific activation modes for enhancing the reactivity of these important ambident pronucleophiles. They can be involved in selective formation of C-C, C-O or C-N bonds leading to various optically active targets in the acyclic and cyclic series including three- to seven-membered ring systems. Recent contributions in the field of biochemical, organometallic and organic catalytic transformations as well as some relevant stoichiometric approaches are discussed from synthetic and mechanistic point of views highlighting some important stereochemical issues.

Catalytic enantioselective desymmetrization of meso-glutaric anhydrides using a stable Ni2-Schiff base catalyst

We describe the desymmetrization of meso-glutaric anhydrides to chiral hemiesters using a bench-stable homodinuclear Ni(2)-(Schiff base) complex as the catalyst in good to excellent yield (up to 99%) and enantioselectivity (up to 94%). Using the opposite enantiomer of the catalyst, we obtained the same yield and enantioselectivity with the opposite configuration, thereby gaining access to both hemiester enantiomers.

Construction of contiguous tetrasubstituted chiral carbon stereocenters via direct catalytic asymmetric aldol and Mannich-type reactions

Catalytic asymmetric synthesis of unnatural amino acids with vicinal tetrasubstituted chiral carbon stereocenters is described. In the first part, direct catalytic asymmetric aldol reaction of simple non-activated ketone electrophiles with α-substituted α-isothiocyanato ester donors was realized. A Mg/Schiff base catalyst promoted the aldol reaction, and α-amino-β-hydroxy esters were obtained in up to 98% ee and 98:2 d.r. In the second part, the Mg/Schiff base catalyst and a Sr/Schiff base catalyst were utilized for stereodivergent direct asymmetric Mannich-type reaction of ketimines. The Mg/Schiff base catalyst gave syn-α,β-diamino esters, while the Sr/Schiff base catalyst produced anti-α,β-diamino esters in good to high enantioselectivity, up to 97% ee.