A novel alkaloid, 17-nor-excelsinidine (1), possessing an unusual 1-azoniatricyclo [4.3.3.0] undecane
moiety was isolated from the twigs and leaves of Alstonia scholaris alongside its biogenetically related
strictamine (2). The structure and absolute stereochemistry of compound 1 were rigorously determined
by a combination of NMR spectroscopy and X-ray crystallography. The 17-nor-excelsinidine (1) and strictamine
(2) showed significant inhibitory activity against herpes simplex virus (HSV) and adenovirus
(ADV).