Enantioselective Approach to the Synthesis of Cyclohexane Carbocyclic Nucleosides

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.

Nucleic acids with a six-membered 'carbohydrate' mimic in the backbone

Starting from pyranose nucleic acids, several series of modified nucleic acids with a six-membered carbohydrate moiety (mimic) have been synthesized and analyzed over a period of 20 years, and this work is summarized here. The process starts with structural and conformational considerations, followed by synthetic efforts and a structural analysis, and ends up with a biological confirmation of the concept, demonstrating that these modified nucleic acids represent very valuable tools in chemistry and biology.

Synthesis of 4/5-Deoxy-4/5-nucleobase Derivatives of 3-O-Methyl-D-chiro-inositol as Potential Antiviral Agents

Using D-pinitol (= 3-O-methyl-D-chiro-inositol) as starting material, a concise synthesis of 4/5-deoxy-4/5-nucleobase derivatives 11-19 has been achieved. The key intermediate 9 was obtained in good yield via an epoxidation from mono-methanesulfonate of D-pinitol. The process of opening of the epoxide ring in 9 by nucleobases appeared to be regioselective in presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). All the synthesized carbocyclic nucleosides were assayed against several viruses and tumors such as HIV-1, HSV-1, and HSV-2, and lung and bladder cancer. However, only compounds 14b, 14a, 16a, 16b, and 19 showed mild inhibitory effect against human lung cancer cell lines (PG) with IC50 values ranging from 50 to 100 microM, and the other compounds did not exhibit any significant antiviral activity or cytotoxicity even at concentrations up to 200 microM.

The cyclohexene ring as bioisostere of a furanose ring: synthesis and antiviral activity of cyclohexenyl nucleosides

The application of the bioisosteric concept between a furanose ring and a cyclohexene ring in the nucleoside field has led to the discovery of new potent antiviral agents.

(D)- and (L)-cyclohexenyl-G, a new class of antiviral agents: synthesis, conformational analysis, molecular modeling, and biological activity

(D)- and (L)-cyclohexeneyl-G were synthesized enantioselectively starting from (R)-carvone. Both show potent and selective anti-herpesvirus activity (HSV-1, HSV-2, VZV, CMV). Molecular modeling demonstrates that both isomers are bound in the active site of HSV-1 thymidine kinase in a high-energy conformation with the base moiety orienting in an equatorial position. It is believed that the flexibility of the cyclohexene ring is essential for their antiviral activity.

The latest progress in the synthesis of carbocyclic nucleosides

This review presents the latest developments in the field of carba-nucleosides (1994-1998). Special attention is paid to the synthesis of key precursors to those carba-nucleosides that possess significant biological activities or have novel structures.