Synthesis of novel carbocyclic nucleoside analogues derived from 7-oxabicyclo[2.2.1]heptane-2-methanol

Catalytic Enantioselective Diels Alder Reaction: Application in the Synthesis of Antiviral Agents

The Diels–Alder reaction (DAR) is one of the most effective and reliable strategies for the construction of six-membered carbocyclic and heterocyclic rings, and it is widely used in the synthesis of organic molecules and drugs. Due to the high regio- and stereo-selectivity and its versatility, DARs have represented a powerful tool for organic chemistry for many years. In addition, the asymmetric DAR has become a fundamental synthetic approach in the preparation of optically active six-membered rings and natural compounds. The COVID-19-related pandemic requires continuous research; DAR represents an useful method to obtain optically active intermediates for the synthesis of antiviral agents under different catalytic conditions. We would like to highlight an intriguing synthetic procedure applied to the development of novel synthetic protocols that are potentially useful against a large panel of viruses and other unmet diseases.

Cycloaddition reactions for antiviral compounds

Prominent in the current stage of drug development, antiviral compounds can be efficiently prepared through cycloaddition reactions. The chapter reports the use of classical Diels–Alder and their hetero version for the design and synthesis of compounds that were tested for their antiviral activities against a variety of viruses. Furthermore, 1,3-dipolar cycloaddition reactions of selected 1,3-dipoles, such as azides, nitrones, and nitrile oxides, are reviewed in the light of their application in the preparation of key intermediates for antiviral synthesis. A few examples of [2+2] cycloaddition reactions are also presented. The products obtained from these pericyclic reaction approaches were all tested for their activities in terms of blocking the virus replication, and the relevant biological data are highlighted.

Crystal structure analysis and sublimation thermodynamics of bicyclo derivatives of a neuroprotector family

The crystal structures of three new structurally related drug-like bicyclo derivatives are correlated with measured thermodynamic quantities for their sublimation and melting processes. The sublimation thermodynamics are determined using the temperature dependencies of the vapour pressure, and the melting processes are examined using differential scanning calorimetry. The three compounds contain a common N-(3-thia-1-azabicyclo[3.3.1]non-2-ylidene)aniline core, with either a CH3, F or CF3 substituent at the 4-position of the aniline ring. Lattice energy calculations are made using both the PIXEL and Coulomb-London-Pauli (CLP) models, and the conformational flexibility of the molecules is examined using gas-phase density functional theory (DFT) calculations. The experimentally measured crystal lattice energies (ΔH(0)sub) decrease in the order: CH3 > F > CF3. The calculated lattice energies using the PIXEL approach are in good agreement with the experimental values, and the partitioned intermolecular interaction energies suggest that dispersion contributions dominate the crystal structures of all three compounds. The sublimation energies and melting points are inversely correlated for the three molecules, with the melting points increasing in the order CF3 < F < CH3.

Design, synthesis, and biological evaluation of novel coxsackievirus B3 inhibitors

The synthesis and SAR study of a novel class of coxsackievirus B3 (CVB3) inhibitors are reported. These compounds could be considered as the 6-chloropurines substituted at position 9 with variously substituted bicyclic scaffolds (bicyclo[2.2.1]heptane/ene-norbornane or norbornene). The synthesis and biological evaluation of 31 target compounds are described. Several of the analogues inhibited CVB3 in the low micromolar range (0.66-2muM). Minimal or no cytotoxicity was observed.

Synthesis of novel racemic carbocyclic nucleosides derived from 5,6-disubstituted norbornene

Novel class of the carbocyclic nucleosides based on bicyclo[2.2.1]heptene/heptane was prepared by two approaches. Thymine analogues were synthesized starting from methyl (1R*,4S*)-bicyclo[2.2.1]hepta-2,5-diene-2-carboxylate1by Michael addition of the thymine salt to the double bond as the key step. The yield and ratio of the isomers of this reaction depended on the used base (DBU, K2CO3). Purine nucleoside analogues were synthesized by the linear synthesis, the purine nucleobase was build-up on the amino group. The amino groups (exo/endoconfiguration) were introduced to the scaffold by the Curtius rearrangement. Norbornene analogues were converted to saturated andcis-hydroxylated nucleoside derivatives. [(1R*,2S*,3S*,4S*)-3-(6-Chloro-9H-purin-9-yl)bicyclo[2.2.1]hept-5-en-2-yl]methanol (13a) and [(1R*,2R*,3R*,4S*)-3-(6-chloro-9H-purin-9-yl)bicyclo[2.2.1]hept-5-en-2-yl]methanol (13b) showed moderate activity againstCoxsackievirus CVB3.