Synthesis, Odour Characteristics, and Antimicrobial Activity of Optically Active Dodecen-4-olides and Their Cyclopropanated Derivatives

Four optically active dodecen-4-olides (1a-d) with carbon-carbon double bonds at different positions and their cyclopropanated derivatives (2a-d) were synthesized, and the odour characteristics of the racemic and optically active compounds were evaluated. Compounds 1a-d and 2a-d exhibited typical lactone-like nuances, characterized by strong top notes and oily middle notes. The position of the carbon-carbon double bond had a significant effect on the odour profile. All 1a-d compounds exhibited different odour characteristics: 1a showed fruity notes, 1b and 1c exhibited green and fruity notes, and 1d exhibited green and floral notes. Cyclopropanation substantially altered these characteristics. As a result, the odour characteristics of compounds 2, where the carbon-carbon double bonds were converted to cyclopropane rings, differed significantly from those of compounds 1. Conversion of the double bond in 1a to a cyclopropane ring changed the fruity note to green note, while cyclopropanation of 1b changed the green note to fruity. The antimicrobial activities of 1 and 2 against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were also investigated. Only compound (S)-1b exhibited antimicrobial activity against S. aureus.