possible conformations, Ilia and IIIb, both of which Intermediates possess unfavorable phenyl-hydrogen interactions. The importance of non-bonded interactions in the transition state of transformations involving substituted 1, 2-ethanolamines has been extensively demonstratedL Recently STOHMER and FRaY z have applied these considerations in the assignment of configuration to the isomeric 1,3-diphenyl-3-amino 1-propanol s. These authors observed that only the fl-isomer in the form of its N-acetyl derivative undergoes N-> O acyl migration under acidic conditions whereas the ~-isomer on successive treatment with phosphorous pentachloride and water is converted irreversibly to the fl-isomer 3. On the basis of these observations and in analogy with the established specificity of these transformations in the