Current Organic Chemistry - Volume 26, Issue 23, 2022

A review of the chemical synthesis of the 1-C-alkyl substituted pyrrolidine and piperidine iminosugar natural products and their analogues (where the alkyl chain comprises two or more carbons) is provided. These syntheses can be grouped into nine different synthetic strategies that share a common approach toward installing the alkyl substituent. These include nucleophilic addition to aldimines; Grignard additions to glycosylamines, cyclic imides, and carbohydrates; Weinreb ketone synthesis; nucleophilic addition to cyclic nitrones; the Overmann rearrangement; the allylation of hemiaminals; and the Petasis borono-Mannich reaction. The broussonetine alkaloids have proven popular synthetic targets to develop new synthetic methods and verify these target molecules' structures and stereochemistry.

In the last two decades, click chemistry has become a modular synthetic procedure to assemble new molecular structures. It is a powerful methodology that relies on the construction of carbon-heteroatom bonds of a variety of reactants. In modern synthetic chemistry, it has been applied in a large number of applications, from pharmaceutical to material science. The copper-catalyzed 1,2,3-triazole preparation, reacting organic azides with alkynes, has become the star of click chemistry due to its reliability and biocompatibility. As a consequence, this reaction has found many applications in diverse areas such as bioconjugation, material science, and drug discovery. In order to understand the effect of copper catalysts and ligands in click chemistry, it is important to understand the structural and mechanistic aspects involved. In this review, several physicochemical aspects of click chemistry are discussed. First, the mechanisms and intermediates involved in the preparation of 1,2,3-triazoles. Second, the different types of copper catalysts are used to perform the reaction regioselectively. The last section shows the structure and characteristics of effective ligands utilized to improve click chemistry under different experimental conditions.

In recent decades, organic synthetic reactions have advanced towards greener and sustainable reactions through the usage of magnetic nanoparticles (MNPs). These MNPs are used as an alternative to resolve the limitations of conventional materials. Amongst various MNPs, iron-based nanoparticles (NPs) are being profoundly explored. The main objective of this review targets to equip its readers a brief introduction to Iron-based MNPs, their properties, evolution and advantage in multicomponent reactions (MCRs) since 2010. MNPs have sown a great impact on multiple fields viz., biomedicine, environmental remediation projects, and catalysis. These are smaller and have a high surface area that allows them to have copious catalytic sites. MNPs can be recovered and reused in various organic syntheses using an external magnet conveniently. MNPs are a sustainable methodology while encountering environmental and profitable advantages. Studies revealed the degradation of catalytic activity after fewer cycles of utilization which is a good research gap to further study on.

Synthesis and isolation of an advanced intermediate (S)-2-Ethylbutyl 2-(((S)-(4- nitrophenoxy) (phenoxy) phosphoryl) amino) propanoate (1b), which is being used for the manufacture of the prodrug diastereoisomer 1d called Remdesivir have been carried out in high yield with efficient stereoselectivity. The isolated advanced intermediate 1b was a diastereoselective nucleoside phosphoramidate prodrug used as an antiviral agent having a mixture of two (SS) and (SR) diastereomers with stereocenter at phosphorus, which was purified by converting into a more stable diastereoselective isomer (SS) by simple physical fractional crystallization process, resulting in an improved yield of ∼45%. The recrystallization has been afforded diastereomerically in 99% pure (SS)-isomer 1b. The 1H NMR characterization data confirm the (SS)-isomer (1b). The developed process holds significant potential for large-scale reactions relatively with commercially available low-cost solvents and co-solvents, resulting in an alternative cheaper process.