Synthesis of 1,2-annulated adamantane heterocycles: structural determination studies of a bioactive cyclic sulfite

The novel heterocycle 3-oxatetracyclo[5.3.1.15,9.02,5]dodecane 4 is prepared by a simple and effective method, involving synthesis of the corresponding 2-hydroxy-1-adamantanomethanol followed by its intramolecular cyclization with thionyl chloride, along with 4-oxo-adamantane-3,5,4-dioxathiane 5 in yields depending on the reaction temperature. Dioxathiane 5 was markedly active against vesicular stomatitis virus, its potency being 2.5-fold higher than that of (S)-9-(2,3-dihydroxypropyl)adenine. NMR data and theoretical calculations on sulfite 5 and the corresponding dioxane 6 suggest that SO is oriented equatorially.