Synthetics
(e)-2-nonenal has a green, fruity aroma reminiscent of cucumbers, watermelon, and redcurrants, often used to enhance rose and geranium notes.
Mosciano, Gerard P&F 16, No. 3, 79, (1991): Green, cucumber, aldehydic, fatty with a citrus nuance
Luebke, William tgsc, (1989): Fatty green cucumber aldehydic citrus
FCI SAS: Powerful fried fatty odor with citrus like background