The S-Thioester Enolate/Imine Condensation: A Shortcut to β-Lactams

Abstract

The condensation between imines and Sthioester metal enolates provides a mild, efficient, and straightforward route

Exceptional Stereoselectivity in the Synthesis of 1,3,4-Trisubstituted 4-Carboxy β-Lactam Derivatives from Amino Acids

“…9 The stereocontrolled Staudinger reaction (ketene-imine cycloaddition), which relies on the use of chiral auxiliaries, and the Gilman- Speeter reaction (enolate-imine condensation), using an enantiomerically pure ester or imine component, are among the most extensively used methodologies to achieve this goal. 10,11 In addition, several examples of the direct catalytic enantioselective synthesis of -lactams have lately been reported. 12 In this context, we have described that the base-promoted cyclization of N-benzyl-N-chloroacetyl amino acid derivatives I affords the corresponding 3-unsubstituted 4-alkyl-4-alkoxycarbonyl-2-azetidinones II (Figure 1).…”

Asymmetric Catalytic Mannich Reactions Catalyzed by Urea Derivatives: Enantioselective Synthesis of β-Aryl-β-Amino Acids

“…β -Amino acid derivatives have proven utility as building blocks for the preparation of pharmaceutical targets, natural products, and peptidic materials with unique structural properties . Of the methods available for their synthesis, ,− the addition of ester enolate equivalents to imines (the Mannich reaction) is especially attractive as it involves the convergent assembly of two units of similar complexity with concomitant formation of a carbon−carbon bond. Various chiral auxiliary and reagent-based approaches to Mannich reactions have been reported for the enantioselective synthesis of β -amino acids.…”

“…Various chiral auxiliary and reagent-based approaches to Mannich reactions have been reported for the enantioselective synthesis of β -amino acids. The development of a catalytic, enantioselective version of this reaction, , however, has proven challenging: the catalyst must be capable of activating imines toward nucleophilic attack, yet be resistant to inhibition by the strongly Lewis-basic amine products. Significant advances have been made recently in the discovery of chiral zirconium-based catalysts for the Mannich reaction. 5a,b These systems, however, are restricted to imine substrates bearing N -aryl substituents with a pendant chelating group for two-point binding to the catalyst.…”

Synthesis of Monothiomalonates – Versatile Thioester Enolate Equivalents for C–C Bond Formations

“…Thioesters are versatile building blocks in organic synthesis as they can be readily transformed into a variety of other functional groups such as aldehydes, ketones, esters, and amides . In comparison to related oxoesters, thioesters are ca .…”