A novel heptaquinane ring system, i.e. Heptacyclo [9.9.0.0^(2,9).0^(3,19).0^(4,8).0^(13,20).0^(14,18)] icosane-4 ,14-dien-5,15-dione (3), was synthesized from an all-cisoid fused pentaquinandiene 1. In this report the production of 3 from pentaquinandione 9 is described , which involves three steps in an overall 40% yield.