Synthesis of 4-hydroxy-β3-homoprolines and their insertion in α/β/α-tripeptides

Synthesis of β-Lactams and β-Homoprolines by Fragmentative Rearrangement of 5-Spirocyclopropaneisoxazolidines Mediated by Acids

Azetidinones and β-amino acids serve as useful building blocks in synthetic organic chemistry and their structural motifs are often found in biologically active compounds. Due to the importance of these compounds, several synthetic strategies have been developed and availability of new synthetic approaches is highly desirable. In this account, we describe the development of an original method that allows the preparation of β-lactam and β-homoproline derivatives not easily accessible through traditional processes. The serendipitous discovery made in our lab in 2000 involved the formation of a β-lactam by heating a mixture of an alkylidenecyclopropane tethered to a formyl group with N-methylhydroxylamine hydrochloride. Investigation of the process resulted in disclosing an alternative synthetic method of azetidinones based on an acid induced fragmentative rearrangement of cycloadducts of nitrones with suitable methylenecyclopropane derivatives. Herein, the scope of this process is reviewed. In addition, both experimental and computational studies of the mechanism for this peculiar fragmentative rearrangement are presented.

Iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters to functionalized pyrrolines

Herein, a new method of iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters to functionalized pyrrolines has been developed. By using readily available substrates, 32 examples of functionalized pyrrolines were prepared in moderate to good yields. Notably, examples of reduction and cycloaddition reactions of the obtained product were given as well.

Iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters with amines

An efficient iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters with amines has been developed.

Copper-catalyzed carbonylative synthesis of pyrrolidine-containing amides from γ,δ-unsaturated aromatic oxime esters

A new method of low-cost copper-catalyzed carbonylative cyclization for preparing pyrrolidine-containing amides from γ,δ-unsaturated aromatic oxime esters and amines has been described.

Configuration-guided reactions: the case of highly decorated spiro[cyclopropane-1,2′(3′H)-pyrrolo[1,2-b]isoxazole] derivatives en route to polyhydroxyindolizidines

The formation of structurally differentiated indolizidinones is guided by a diverse behaviour of spirocyclopropaneisoxazolidine precursors under fluorination reactions.