Structure of a propynyl adduct of an oxa-bridged octalin.

C20H30O6, Mr = 366.45, monoclinic, P2l/n, a = 10.411 (2), b = 16.084 (3), c = 11.991 (1) A, beta = 100.98 Mg m-3, Mo Ka, lambda V 0.71069 A, mu = 0.097 (2) degrees, V = 1971 (6) A3, Z = 4, Dx = 1.23 Mg m-3, Mo Ka, lambda = 0.71069 A, mu = 0.097 mm-1, F(000) = 792, T = 296 K, R = 0.050, wR = 0.065 for 3430 observed unique reflections. The structure of a key synthetic intermediate for use in a total synthesis of the nargenicin antibiotics has been established by X ray single-crystal methods. Its structure is characterized by an essentially strain-free tricyclic oxa-bridged octalin nucleus, low-energy methoxymethyl ether side-chain conformations and an intramolecular hydrogen bond between the hydroxyl group hydrogen atom and a methoxymethyl ether oxygen atom. Intermolecular packing contacts less than the sum of van der Waals radii consist of weak C-H...O interactions.