Improved synthesis of 15-deoxyspergualin analogs using the Ugi multi-component reaction

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.

Brønsted Acid-Catalyzed Synthesis of 1,2,5-Trisubstituted Imidazoles via a Multicomponent Reaction of Vinyl Azides with Aromatic Aldehydes and Aromatic Amines

A facile and efficient approach to the synthesis of 1,2,5-trisubstituted imidazoles is developed via a multicomponent reaction under metal-free catalysis. Under Brønsted acid catalysis, the desired products can be obtained from readily available vinyl azides, aromatic aldehydes, and aromatic amines without generating any toxic waste. The convenient operations and high functional group compatibility indicate that this approach offers an attractive alternative method for the synthesis of imidazole derivatives.

Potent Inhibition of Nicotinamide N-Methyltransferase by Alkene-Linked Bisubstrate Mimics Bearing Electron Deficient Aromatics

Nicotinamide N-methyltransferase (NNMT) methylates nicotinamide (vitamin B3) to generate 1-methylnicotinamide (MNA). NNMT overexpression has been linked to a variety of diseases, most prominently human cancers, indicating its potential as a therapeutic target. The development of small-molecule NNMT inhibitors has gained interest in recent years, with the most potent inhibitors sharing structural features based on elements of the nicotinamide substrate and the S-adenosyl-l-methionine (SAM) cofactor. We here report the development of new bisubstrate inhibitors that include electron-deficient aromatic groups to mimic the nicotinamide moiety. In addition, a trans-alkene linker was found to be optimal for connecting the substrate and cofactor mimics in these inhibitors. The most potent NNMT inhibitor identified exhibits an IC₅₀ value of 3.7 nM, placing it among the most active NNMT inhibitors reported to date. Complementary analytical techniques, modeling studies, and cell-based assays provide insights into the binding mode, affinity, and selectivity of these inhibitors.

A Practical Approach for the Synthesis of Novel Triazolo-fused Benzazepine Derivatives Using a Multi-component Reaction and an Intramolecular C–H Arylation

An efficient and straightforward method has been developed for the preparation of triazolo-fused benzazepines by a facile, one-pot Ugi multi-component reaction/click reaction. In this strategy, the Ugi-reaction products were coupled by a click reaction, thus integrating the triazole fragment into the benzazepine structure using an intramolecular C–H arylation. The corresponding products were obtained in good yields without unfavourable by-products.

Concise Synthesis of Spergualin-Inspired Molecules With Broad-Spectrum Antibiotic Activity

There is a growing need to identify new, broad-spectrum antibiotics. The natural product spergualin was previously shown to have promising anti-bacterial activity and a privileged structure, but its challenging synthesis had limited further exploration. For example, syntheses of spergualin and its analogs have been reported in approximately 10 linear steps, with overall yields between 0.3 and 18%. Using the Ugi multi-component reaction, we assembled spergualin-inspired molecules in a single step, dramatically improving the overall yield (20% to 96%). Using this strategy, we generated 43 new analogs and tested them for anti-bacterial activity against two Gram-negative and four Gram-positive strains. We found that the most potent analogue, compound 6, had MIC values between 4 and 32 μg/mL against the six strains, which is a significant improvement on spergualin (MIC ∼ 6.25 to 50 μg/mL). These studies provide a concise route to a broad-spectrum antibiotic with a novel chemical scaffold.

The chemistry and biology of organic guanidine derivatives

The chemistry and biology of organic natural guanidines are reviewed, including the isolation, structure determination, synthesis, biosynthesis and biological activities of alkaloids, non-ribosomal peptides, guanidine-bearing terpenes, polyketides and shikimic acid derivatives from natural sources.