Recent developments in the total synthesis of natural products using the Ugi multicomponent reactions as the key strategy

The total syntheses of selected natural products using different versions of the Ugi multicomponent reaction is reviewed on a case-by-case basis. The revision covers the period 2008-2023 and includes detailed descriptions of the synthetic sequences, the use of state-of-the-art chemical reagents and strategies, as well as the advantages and limitations of the transformation and some remedial solutions. Relevant data on the isolation and bioactivity of the different natural targets are also briefly provided. The examples clearly evidence the strategic importance of this transformation and its key role in the modern natural products synthetic chemistry toolbox. This methodology proved to be a valuable means for easily building molecular complexity and efficiently delivering step-economic syntheses even of intricate structures, with a promising future.

Stabilizing Pseudouridimycin: Synthesis, RNA Polymerase Inhibitory Activity, and Antibacterial Activity of Dipeptide-Modified Analogues

Pseudouridimycin (PUM) is a microbially produced C-nucleoside dipeptide that selectively targets the nucleotide addition site of bacterial RNA polymerase (RNAP) and that has a lower rate of spontaneous resistance emergence relative to current drugs that target RNAP. Despite its promising biological profile, PUM undergoes relatively rapid decomposition in buffered aqueous solutions. Here, we describe the synthesis, RNAP-inhibitory activity, and antibacterial activity of chemically stabilized analogues of PUM. These analogues feature targeted modifications that mitigate guanidine-mediated hydroxamate bond scission. A subset of analogues in which the central hydroxamate is replaced with amide or hydrazide isosteres retain the antibacterial activity of the natural product.

Nucleoside analogues: N-glycosylation methodologies, synthesis of antiviral and antitumor drugs and potential against drug-resistant bacteria and Alzheimer's disease

Nucleosides have gained significant attention since the discovery of the structure of DNA. Nucleoside analogues may be synthesized through multiple synthetic pathways, however the N-glycosylation of a nucleobase is the most common method. Amongst the different classical N-glycosylation methodologies, the Vorbrüggen glycosylation is the most popular method. This review focuses on the synthesis and therapeutic applications of several FDA approved nucleoside analogues as antiviral and anticancer agents. Moreover, this review also focuses on the potential of these compounds as new antibacterial and anti-Alzheimer's disease agents, offering an overview of the most recent research in these fields.

Total synthesis of pseudouridimycin and its epimer via Ugi-type multicomponent reaction

A total synthesis of pseudouridimycin (1) was accomplished featuring an unusual oxime Ugi-type multicomponent condensation to simultaneously construct the dipeptide moiety of this peptidyl nucleoside antibiotic. In this synthetic route 1 is readily accessible via a longest linear sequence of 9 synthetic steps from pseudouridine. This strategy can be applicable to a variety of pseudouridimycin analogues.

Beyond the approved: target sites and inhibitors of bacterial RNA polymerase from bacteria and fungi

Covering: 2016 to 2022RNA polymerase (RNAP) is the central enzyme in bacterial gene expression representing an attractive and validated target for antibiotics. Two well-known and clinically approved classes of natural product RNAP inhibitors are the rifamycins and the fidaxomycins. Rifampicin (Rif), a semi-synthetic derivative of rifamycin, plays a crucial role as a first line antibiotic in the treatment of tuberculosis and a broad range of bacterial infections. However, more and more pathogens such as Mycobacterium tuberculosis develop resistance, not only against Rif and other RNAP inhibitors. To overcome this problem, novel RNAP inhibitors exhibiting different target sites are urgently needed. This review includes recent developments published between 2016 and today. Particular focus is placed on novel findings concerning already known bacterial RNAP inhibitors, the characterization and development of new compounds isolated from bacteria and fungi, and providing brief insights into promising new synthetic compounds.