Synthesis, odour characteristics, and antibacterial activity of optically active cognac lactones

In this study, all stereoisomers of cognac lactone ( 1 ) were synthesized with over 99% enantiomeric excess via diastereomeric resolution using N ‐benzyloxycarbonyl‐ l ‐proline ( N ‐Cbz‐ l ‐proline) as a resolving agent. N ‐Cbz‐ l ‐proline could be applied for the diastereomeric resolution of both syn ‐ and anti ‐forms and yielded all diastereomers in over 99% diastereomeric excess. The odour properties of racemic and optically active 1 were evaluated for their orthonasal aromas. All the stereoisomers had different odour characteristics and thresholds. In general, the (3 S )‐ and (3 R )‐forms had fruity and herbal notes, respectively, and (3 R ,4 S )‐ 1 had the lowest odour threshold at 0.01 ppm. All stereoisomers, except (3 R ,4 S )‐ 1 , showed antibacterial activity against Staphylococcus aureus . Moreover, (3 S ,4 S )‐ 1 showed high antibacterial activity against both S aureus and Escherichia coli .