X-Ray crystal structure analysis of methyl N- bromoacetylhomosecodaphniphyllate, C25H38BrNO3, has established the constitution and absolute stereochemistry of secodaphniphylline and methyl homosecodaphniphyllate, alkaloids of a new type from Daphniphyllum macropodum Miquel. The crystals are orthorhombic, of space group P212121, with Z = 4 in a unit cell of dimensions a = 15.726, b = 14.981, c = 10.346 Å. The structure was elucidated by the heavy-atom method and refined by Fourier and least-squares calculations. The final R value with 1318 independent reflections is 0.084. The absolute stereochemistry was determined by the anomalous dispersion method. By comparison with these results, the absolute stereochemistries of other daphniphyllum alkaloids, daphniphylline and yuzurimine, have also been assigned.