A Brief Review on the Development of Novel Potentially Active Azetidin-2-ones Against Cancer

Modular enantioselective access to β-amino amides by Brønsted acid-catalysed multicomponent reactions

β-Amino acids are structural motifs widely found in therapeutic natural products, novel biomimetic polymers and peptidomimetics. As a convergent method, the synthesis of stereoenriched β-amino amides through the asymmetric Mannich reaction requires specialized amide substrates or a metal catalyst for enolate formation. By a redesign of the Ugi reaction, a conceptually different solution to prepare chiral β-amino amides was established using ambiphilic ynamides as two-carbon synthons. The modulation of ynamides or oxygen nucleophiles concisely furnished three classes of β-amino amides with generally good efficiency as well as excellent chemo- and stereo-control. The utility is verified in the preparation of over 100 desired products that bear one or two contiguous carbon stereocentres, including those that directly incorporate drug molecules. This advance also provides a synthetic shortcut to other valuable structures. The amino amides could be elaborated into β-amino acids, anti-vicinal diamines, γ-amino alcohols and β-lactams or undergo transamidation with amino acids and amine-containing pharmaceuticals.

Directed Copper-Catalyzed Tandem Radical Cyclization Reaction of Alkyl Bromides and Unactivated Olefins

The free radical cyclization reaction is a promising strategy for ring framework formation. Herein, we report a copper-catalyzed tandem radical cyclization strategy for preparing substituted lactam derivatives. This reaction proceeds through a radical coupling approach, which not only allows a wide range of alkenes but also is quite compatible with the primary, secondary, and tertiary radicals. In addition, density functional theory calculations were performed to gain insights into the reaction mechanism.

One-Pot Construction of Diverse β-Lactam Scaffolds via the Green Oxidation of Amines and Its Application to the Diastereoselective Synthesis of β-Amino Acids

In this study, a simple one-pot construction of β-lactam scaffolds was successfully achieved via 4,6-dihydroxysalicylic acid-catalyzed organocatalytic oxidation of amines to imines using molecular oxygen. Although some imines are highly unstable and difficult to isolate by conventional methods, the organocatalytic oxidation of amines described herein, followed by their direct reaction with acyl chlorides in the presence of a base, afforded a series of new β-lactam derivatives with excellent cis selectivity, which could not be synthesized and isolated by previously reported methods. Thus, this one-pot protocol will be one of the powerful methods applicable to the synthesis of various potential drug candidates and functional molecules. Furthermore, the subsequent hydrolysis of these β-lactams successfully afforded the corresponding β-amino acids as almost single diastereomers in up to 99% yields.