Reactions of Acid Chlorides/Ketenes with 2-Substituted 4,5-Dihydro-4,4-dimethyl-1,3-thiazoles: Formation of Penam Derivatives

Acyclic Twisted Amides

In this contribution, we provide a comprehensive overview of acyclic twisted amides, covering the literature since 1993 (the year of the first recognized report on acyclic twisted amides) through June 2020. The review focuses on classes of acyclic twisted amides and their key structural properties, such as amide bond twist and nitrogen pyramidalization, which are primarily responsible for disrupting nN to π*C═O conjugation. Through discussing acyclic twisted amides in comparison with the classic bridged lactams and conformationally restricted cyclic fused amides, the reader is provided with an overview of amidic distortion that results in novel conformational features of acyclic amides that can be exploited in various fields of chemistry ranging from organic synthesis and polymers to biochemistry and structural chemistry and the current position of acyclic twisted amides in modern chemistry.

Synthetic Approaches toward Monocyclic 3-Amino-β-lactams

Due to the emerging resistance against classical β-lactam-based antibiotics, a growing number of bacterial infections has become harder to treat. This alarming tendency necessitates continued research on novel antibacterial agents. Many classes of β-lactam antibiotics are characterized by the presence of the 3-aminoazetidin-2-one core, which resembles the natural substrate of the target penicillin-binding proteins. In that respect, this Review summarizes the different synthetic pathways toward this key structure for the development of new antibacterial agents. The most extensively applied methods for 3-amino-β-lactam ring formation are discussed, in addition to a few less common strategies. Moreover, approaches to introduce the 3-amino substituent after ring formation are also covered.