Synthetic studies towards bioactive frondosins: rapid framework access and diversity creation

(1′S,6′S,8′S,9′R)-9′-Bromo-12′-oxaspiro[1,3-dioxolane-2,4′-tricyclo[6.3.1.01,6]dodecane]

In an endeavor directed towards the construction of the oxabicyclic[3.2.1]octane segment present in the bioactive natural products of cortistatins and icetexanes genre, the title compound, C₁₃H₁₉BrO₃, was synthesized from (4aR,9aS)-1,3,4,4a,5,6,9,9a-octa­hydro­spiro­[benzo[7]annulene-2,2′-[1,3]dioxolane]-4a-ol via a transannular bromo-etherification protocol. The six-membered ring adopts a twist-boat conformation, while the fused cycloheptane ring adopts a chair conformation. The crystal packing is effected through two distinct inter­molecular C—H⋯O hydrogen-bond patterns and mol­ecules are arranged to define an inter­esting motif along the b axis.