The new alkaloid lilidine, isolated for the first time from the epigeal part of Lilium martagon has been studied by special methods. It has the composition B5H6NO2, mp 118-110°C, [α]D-26.3°. The1H and13C NMR spectra were studied in detail. The values of the direct and long-range spin-spin coupling constants between the13C carbon nuclei and the1H nuclei of the alkaloid molecule were measured with the aid of13C-[{su1}H] selective heteronuclear double resonance. The structure of 5-hydroxy-3-methyl-3-pyrrolin-2-one is suggested for lilidine. © 1988 Plenum Publishing Corporation.