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 (1R*,5S*,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 AlCl3‐catalyzed Diels‐Alder reaction is reported.