Synthesis and properties of (+)-ketopinic and (-)-camphanic acids esters bearing a nitrogen-containing heterocycle

A three-stage method was proposed for the synthesis of (1 S )-(+)-camphor-10-sulfonic acid, (+)-ketopinic and (-)-camphanic acids esters containing a saturated nitrogen-containing heterocycle. It was found that (1 S )-(+)camphor-10-sulfonic acid esters undergo destruction with elimination of the sulfonic acid group in substitution reactions involving nitrogen-containing heterocycles. Esters of (+)-ketopinic and (-)-camphanic acids were formed during the proposed synthetic route, but undergo transesterification under column chromatography conditions. Quantum chemical calculations showed that the destruction of the ester bond in the case of (+)-ketopinic and (-)-camphanic acids requires less energy than the breaking of a similar bond in (-)-borneol esters. It was revealed that the internal bond strength index (IBSI) for the alkyl C-O bond in (-)-borneol esters is higher than in (+)-ketopinic and (-)-camphanic acid esters. Antiviral properties against the H1N1 influenza virus were studied for derivatives of (+)-ketopinic and (-)-camphanic acids.