Synthesis and odour evaluation of double‐bond isomers of DAMASCENOLIDE, 4‐(4‐methylpent‐3‐en‐1‐yl)‐2(5H)‐furanone, which has a citrus‐like odour

Our group recently isolated 4‐(4‐methylpent‐3‐en‐1‐yl)‐2(5H)‐furanone (DAMASCENOLIDE or MPF), which has a citrus‐like odour, from damask rose (Rosa damascena). DAMASCENOLIDE has two double bonds, and we were interested in how the position and the geometric isomerism of these double bonds change the odour. Therefore, we synthesized eleven novel double‐bond isomers of DAMASCENOLIDE and evaluated their odours. Some of them have similar odours to DAMASCENOLIDE, while many others have different odours such as metallic, tropical and fishy. Especially, a Z‐form double‐bond moiety changed the odour significantly. Regarding the odour intensity, compounds with 2(3H)‐furanone skeleton tend to be stronger than compounds with 2(5H)‐furanone skeleton. From these results, it was found that the position and the geometric isomerism of the double bond greatly affected the odour. We synthesized eleven novel double‐bond isomers of DAMASCENOLIDE and evaluated their odours. Many compounds have different odours from DAMASCENOLIDE, such as metallic, tropical and fishy. From these results, it was found that the position and the geometric isomerism of the double bond greatly affected the odour.