Structure, conformation and absolute configuration of novel bisnorsesquiterpenes from the Adesmia boronioides essential oil

Two novel bisnorsesquiterpenes (1R,4S,5R)-esquel-6-en-9-one () and (1R,4S,5S)-esquel-7-en-9-one () were isolated from the essential oil of Adesmia boronioides. Their structures and relative stereochemistry were elucidated by 1D and 2D NMR data, including carbon–carbon connectivity and NOESY experiments. The absolute configuration was determined by chemical conversion of into phenol , whose Cotton effect was compared with that of cacalol. The conformational behavior of the new compounds containing the hydrindane skeleton was studied by molecular mechanics. Compound possesses a very pleasant fruity odor.