Organometallic Enantiomeric Scaffolding. A Molybdenum-Mediated Intramolecular Nucleophilic Ketalization−Demetalation Cascade. Total Synthesis of (+)-(1R,2S,5S,7R)-2-Hydroxy-exo-brevicomin

TpMo(CO)₂(5-oxo-η³-pyranyl) scaffolds bearing an internal alkoxide undergo a novel intramolecular nucleophilic ketalization reaction. The anionic intermediate is easily demetalated, rapidly providing the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework in moderate to good yields with high enantiopurity. An enantiocontrolled total synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin was accomplished utilizing the reaction sequence.