Daphcalycine, a novel heptacycle fused ring system alkaloid from Daphniphyllum calycinum

A novel Daphniphyllum alkaloid, daphcalycine (1), was isolated together with known daphnicyclidin D (2) from the stem bark of Daphniphyllum calycinum. The highly condensed polycyclic structure, established by spectral analysis, possessed an unusual framework: a central quinuclidine like tricycle produced by fusion of a piperidine, a tetrahydropyran, and an oxazine ring in turn condensed to surrounding three penta-, one hexa-, and one hepta-membered rings. The relative configuration of 11 carbon stereocenters of 1 was elucidated on the basis of NOESY.