Microwave-assisted synthesis of borneol esters and their antimicrobial activity

Seventeen borneol esters (1–17) were synthesised by conventional and microwave-assisted methodology using DIC/DMAP, and seven are described for the first time (8, 9, 10, 12, 13, 16 and 17). The microwave-assisted methodology was carried out without use of solvents, displayed short reaction times, and showed equal or higher yields for all the long-chain esters and three aromatic compounds (11, 12 and 14) when compared to the conventional approach. All the borneol esters were evaluated against the bacteria Streptococcus sanguinis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungus Candida albicans. Compounds 12, 13 and 14 displayed promising antibacterial activity with a MIC equal to ampicilin (62.5 mg mL⁻¹) for some microorganisms. In fact, bornyl 3′,4′-dimethoxybenzoate (13) was active against all tested bacteria and fungus.