chiral one-dimensional chain via intermolecular hydrogenbonding. In the case of phosphine oxides, their oxygen always acts as a hydrogen acceptor of the hydrogenbonding. Thus, (2-oxo-1,2-dihydro-x-pyridyl)diphenylphosphine oxides (x = 3: 3a and 5: 3b) form hydrogenbonds intermolecularly between the oxygen atom on the phosphoryl group and the hydrogen atom on nitrogen to construct a chiral or an achiral