Myrobotinol (1) was isolated from the leaves of Myrioneuronnutans (Rubiaceae) and its structure determined from spectraldata, including mass spectrometry and 2D NMR. Thiscompound presents a new hexacyclic alkaloid skeletonincluding a 1,3-oxazine and aminal functionality. Theabsolute configuration of myrobotinol was established byusing Mosher's method. A plausible biosynthetic pathwaystarting from l-lysine via Δ-piperideine was proposed forthis hexacyclic alkaloid.