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Five pairs of new orcinol-based merosesquiterpenoid enantiomers, named dauresorcinols A−E (1−5), were isolated from the leaves of Rhododendron dauricum. Their structures were elucidated by comprehensive spectroscopic data analysis, quantum chemical calculations, Rh2(OCOCF3)4-induced ECD, and single-crystal X-ray diffraction analysis. Dauresorcinols A (1) and B (2) possess two unprecedented merosesquiterpene skeletons featuring a novel 6,7-dimethyl-11-oxatetracyclo[8.8.0.02,7.012,17]octadecane and a caged 15-isohexyl-2,10-dioxatetracyclo[7.4.1.111,14.03,8]pentadecane motif, respectively. Plausible biogenetic pathways of 1−5 are proposed involving key oxa-electrocyclization and Wagner−Meerwein rearrangement reactions. (+)/(−)-1 and 3−5 showed potent α-glucosidase inhibitory activity, 3 to 22 times stronger than acarbose, an antidiabetic drug targeting α-glucosidase. Docking results provide a basis to design and develop meroterpenoids as novel α-glycosidase inhibitors.