[reaction: see text]. A unique domino reaction of alpha-nitrocycloalkanones with alpha-alkyl alpha,beta-unsaturated aldehydes in aqueous base was discovered, leading to the one-pot synthesis of hitherto unknown functionalized, bridged, bicyclic lactones containing 10-, 11-, 13-, and 15-membered rings. The structures of these heterocyclic compounds, containing also an unusual 6-hydroxy-1,2-oxazine ring, were determined by spectral and single-crystal X-ray diffraction studies.