Elatenyne—a Pyrano[3,2-B]Pyranyl Vinyl Acetylene From the Red Alga Laurencia elata

Elatenyne (3,7-dibromo-6-ethyl-2-(pent-2′-en-4′-ynyl ) octahydropyrano [3,2-b] pyran ) was isolated as an oil from the marine red alga Laurencia elata. Its structure and those of three derivatives were assigned on the basis of spectroscopic, predominantly n.m.r ., data.