Unlocking Enol-Ugi-Derived Conformationally Restricted Peptidomimetic Motifs

The enol-Ugi condensation, a versatile multicomponent reaction, provides a rapid and efficient route to enamine peptidomimetics. In this study, we investigated the factors influencing the conformational behavior of three enol-Ugi adducts with distinct structural features. Through DFT calculations and NCI analysis, we identified that noncovalent interactions, including hydrogen bonds and π-π interactions, play a pivotal role in restricting conformational flexibility. While six-membered cyclic enamines 6 and 7 exhibited varying degrees of rotational freedom, the indanone-derived enamine 8 displayed a locked conformation resembling a retropeptidic turn. These findings highlight the potential of tailoring enol-Ugi adducts to mimic biologically relevant peptidic motifs, opening new avenues for drug discovery and design.

Recent Advances in the Synthesis of Peptidomimetics via Ugi Reactions

Peptidomimetics have been extensively explored in many area due to their ability to improve pharmacological qualities and interesting biological activities. Cycles could be incorporated in peptides to reduce their flexibility, often enhancing the affinity for a certain receptor. Many efforts have been made to synthesize various peptidomimetics. Among them, the Ugi reaction is a popular way for the synthesis of peptidomimetics because it provides peptide-like products. The Ugi reaction consists of the condensation of an aldehyde or ketone, a carboxylic acid, an amine, and an isocyanide usually giving a linear peptidomimetic. In order to obtain other linear, cyclic or polycyclic peptidomimetics, the acyclic products have to undergo additional transformations or cyclizations. This review covers the years from 2018-2023, regarding the synthesis of linear, cyclic and polycyclic peptidomimetics, employing Ugi reactions eventually followed by post-Ugi transformations. Organo-catalyzed reactions, base-promoted reactions, and metal-free reactions toward peptidomimetics are highlighted.

Transition Metal-Free N-S Bond Cleavage and C-N Bond Activation of Ugi-Adducts for Rapid Preparation of Primary Amides and α-Ketoamides

A novel method of transition metal-free N-S bond cleavage and subsequent C-N bond activation of Ugi-adducts was developed. Diverse primary amides and α-ketoamides were prepared in a rapid, step-economical and highly efficient manner in two steps. This strategy features excellent chemoselectivity, high yield and functional-group tolerance. Primary amides derived from the pharmaceuticals probenecid and febuxostat were prepared. This method opens a new pathway for the simultaneous synthesis of primary amides and α-ketoamides in an environmentally friendly manner.