Glaulactams A-C (1-3), which possess a novel skeleton, as well as the known compound daphmanidin B (4), were isolated from the leaves of Daphniphyllum glaucescens and separated using ion-exchange chromatography aided by NMR fingerprinting. Their structures, including their absolute configurations, were elucidated by spectroscopic analyses and time-dependent density-functional-theory-calculated electronic circular dichroism spectra; the data were subsequently analyzed to gain insight into the respective biogenetic relationships between the isolates, which exhibited anti-H1N1 and immunosuppressive activities.