Identification and Synthesis of New γ‐Lactones from Tuberose Absolute ( Polianthes tuberosa )

Six unsaturated γ‐lactones, ( Z )‐5‐octen‐4‐olide ( 1 ), ( Z )‐5‐decen‐4‐olide ( 2 ).( Z )‐6‐nonen‐4‐olide ( 3 ), ( Z )‐6‐dodecen‐4‐olide ( 4 ), ( Z , Z )‐6,9‐dodecadien‐4‐olide ( 5 ), and tuberolide ( 6 ) have been identified for the first time in tuberose absolute (from Polianthes tuberosa L.). All structures were corroborated by synthesis and all, except 3 and 4 , are new. The name ‘tuberolactone’ has been suggested for ( Z , Z )‐2,7‐decadien‐5‐olide [1]. We propose the name ‘tuberolide’ for the bicyclic lactone 6 . (IUPAC name (1 R *,5 S *, Z )‐6‐(2′‐pentenyl)‐2‐oxabicyclo[3.3.0]octan‐3‐one). An improved method for the stereoselective synthesis of (±)‐ cis ‐bicyclo [4.3.0]‐non‐3‐en‐7‐one ( 23 ) by an AlCl 3 ‐catalyzed Diels‐Alder reaction is reported.