Asymmetric syntheses of 8-oxabicyclo[3,2,1]octane and 11-oxatricyclo[5.3.1.0]undecane from glycals† †Electronic supplementary information (ESI) available: Experimental procedures and characterisation data for all compounds are provided. CCDC 1436794 and 1520731. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc02625k Click here for additional data file. Click here for additional data file.

Chiral 8-oxabicyclo[3.2.1]octane and 11-oxatricyclo[5.3.1.0]undecane are common structural motifs featured in many classes of natural products (Fig. 1), some of which show interesting biological activities. Englerin A, a potential anti-tumor reagent, is isolated from Phyllanthus engleri in Tanzania and shows selective activity to renal cancer cell lines at the nanomolar level. Balsamiferine J, isolated from Blumea balsamifera, represents a novel type of sesquiterpenoids with NO inhibitory activity against murine microglial cell lines. Homalomenol C, isolated from the roots of Homalomena aromatica, is reported as the bioactive component of the Vietnamese traditional medicine as an anti-inammatory agent. Driven by their important bioactivities, many chemists are interested in the synthesis of this type of natural products. Attempts to gain access to this unique 8-oxabicyclo[3.2.1]octane ring asymmetrically include [4 + 3], [5 + 2], [3 + 2] cycloadditions and cascade reactions. Despite achieving moderate to good diastereoselectivities, these methods suffer from the drawbacks of requiring expensive chiral metal