Quaternized α,α'-Amino Acids via Curtius Rearrangement of Substituted Malonate-Imidazolidinones.

An efficient synthesis protocol is presented for accessing quaternized α-amino acids in chiral, nonracemic form via diastereoselective malonate alkylation followed by C- to N-transposition. The key stereodifferentiating step involves a diastereoselective alkylation of an α-monosubstituted malonate-imidazolidinone, which is followed first by a chemoselective malonate PMB ester removal and then a Curtius rearrangement to provide the transposition. The method demonstrates a high product ee (89-99% for eight cases) for quaternizing a range of proteinogenic α-amino acids. The stereogenicity in targets 5a-i supports previous conclusions that the diastereoselective alkylation step proceeds via an α-substituted malonate-imidazolidinone enolate in its Z-configuration, with the auxiliary in an s-transC-N conformation.

Catalytic enantioselective acyl transfer: the case for 4-PPY with a C-3 carboxamide peptide auxiliary based on synthesis and modelling studies.

A series of 4-pyrrolidinopyridine (4-PPY) C-3 carboxamides containing peptide-based side chains have been synthesised and evaluated in the kinetic resolution of a small library of chiral benzylic secondary alcohols. A key design element was the incorporation of a tryptophan residue in the peptide side chain for promoting π-stacking between peptide side chain and the pyridinium ring of the N-acyl intermediate, in which modelling was used as a structure-based guiding tool. Together, a catalyst containing a LeuTrp-N-Boc side chain (catalyst 8) was identified that achieved s-values up to and in slight excess of 10. A transition-state model based on the modelling is proposed to explain the origin of enantioselectivity. This study establishes the usefulness of modelling as a structure-based guiding tool for enantioselectivity optimization as well as the potential for developing scalable peptide-based DMAP-type catalysts for large-scale resolution work.

A Mini Review on Emerging Targets and Approaches for the Synthesis of Anti-viral Compounds: In Perspective to COVID-19.

The novel Coronavirus disease (COVID-19) is an epidemic disease that appeared at the end of the year 2019 with a sudden increase in number and came to be considered as a pandemic disease caused by a viral infection which has threatened most countries for an emergency search for new anti-SARS-COV drugs /vaccines. At present, the number of clinical trials is ongoing worldwide on different drugs i.e. Hydroxychloroquine, Remedisvir, Favipiravir that utilize various mechanisms of action. A few countries are currently processing clinical trials, which may result in a positive outcome. Favipiravir (FPV) represents one of the feasible treatment options for COVID-19, if the result of the trials turns out positive. Favipiravir will be one of the developed possibly authoritative drugs to warrant benefits to mankind with large-scale production to meet the demands of the current pandemic Covid-19 outbreak and future epidemic outbreaks. In this review, the authors tried to explore key molecules, which will be supportive for devising COVID-19 research.