Asymmetric synthesis of unusual fused tricyclic beta-lactam structures via aza-cycloadditions/ring closing metathesis

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.

The endo-aza-Michael addition in the synthesis of piperidines and pyrrolidines

Intramolecular endo-aza-Michael additions are categorised in various ways.

Recent developments in the synthesis of condensed β-lactams

β-Lactams are important heterocycles with diverse pharmacological profiles and have emerged as useful organic synthons.

Investigation of the Passerini and Ugi reactions in β-lactam aldehydes. Synthetic applications

Ugi and Passerini multicomponent reactions on 4-oxoazetidine-2-carboxaldehydes allow the straightforward synthesis of highly functionalized β-lactams.

Macrocycle-embedded β-lactams as novel inhibitors of the Penicillin Binding Protein PBP2a from MRSA

Assuming that bicyclic β-lactams endowed with high conformational adaptability should more easily form acyl-enzyme complexes with PBP2a than the traditional antibiotics, we have prepared a series of bis-2-oxo-azetidinyl macrocycles as potential inhibitors. The compounds are formally "head-head" (HH) cyclodimers of 1-(ω-alkenoyl)-3-(S)-(ω'-alkenoylamino)-2-azetidinones, with various lengths of the alkene chains, obtained by two successive metathesis reactions using the Grubbs catalyst. All compounds behave as acylating inhibitors of PBP2a and one β-lactam (5c), embedded into the largest ring (32 atoms), features an activity close to that of Ceftobiprole. Conformational analyses, theoretical reactivity models and docking experiments in PBP2a cavity allow to propose a novel pharmacophore, i.e. the 3-(S)-acylamino-1-acyl-2-azetidinone ring, with the syn-conformation of the imide function, associated to a flexible macrocycle favoring the opening of the active site.

New and concise syntheses of the bicyclic oxamazin core using an intramolecular nitroso Diels-Alder reaction and ring-closing olefin metathesis

Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels-Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems.

Stereoselective Synthesis of Quaternary Proline Analogues

This review describes available methods for the diastereoselective and asymmetric synthesis of quaternary prolines. The focus is on the preparation of alpha-functionalized prolines with the pyrrolidine moiety not embedded in a polycyclic frame. The diverse synthetic approaches are classified according to the bond which is formed to complete the quaternary skeleton.