Microwave-assisted synthesis of borneol esters and their antimicrobial activity

<p>Seventeen borneol esters (<b>1</b>–<b>17</b>) were synthesised by conventional and microwave-assisted methodology using DIC/DMAP, and seven are described for the first time (<b>8</b>, <b>9</b>, <b>10</b>, <b>12</b>, <b>13</b>, <b>16</b> and <b>17</b>). 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 (<b>11</b>, <b>12</b> and <b>14)</b> when compared to the conventional approach. All the borneol esters were evaluated against the bacteria <i>Streptococcus sanguinis</i>, <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i> and the fungus <i>Candida albicans</i>. Compounds <b>12</b>, <b>13</b> and <b>14</b> displayed promising antibacterial activity with a MIC equal to ampicilin (62.5 mg mL<sup>−1</sup>) for some microorganisms. In fact, bornyl 3′,4′-dimethoxybenzoate (<b>13</b>) was active against all tested bacteria and fungus.</p>