Diastereotopic groups in two new single-enanti-omer structures ( R 2 )P(O)[NH-(+)CH(C 2 H 5 )(C 6 H 5 )] ( R = OC 6 H 5 and C 6 H 5 ).

The crystal structures of two single-enanti-omer compounds, i.e. diphenyl [( R )-(+)-α-ethyl-benzyl-amido]-phosphate, C 21 H 22 NO 3 P or (C 6 H 5 O) 2 P(O)[NH-( R )-(+)CH(C 2 H 5 )(C 6 H 5 )] ( I ), and N -[( R )-(+)-α-ethyl-benz-yl]- P , P -di-phenyl-phosphinic amide, C 21 H 22 NOP or (C 6 H 5 ) 2 P(O)[NH- R -(+)CH(C 2 H 5 )(C 6 H 5 )] ( II ), were studied. The different environments at the phospho-rus atoms, (O) 2 P(O)(N) and (C) 2 P(O)(N), allow the P=O/P-N bond strengths to be compared, as well as the N-H⋯O=P hydrogen-bond strengths, and P=O/N-H vibrations. The following characteristics related to diastereotopic C 6 H 5 O/C 6 H 5 groups in I / II were considered: geometry parameters, contributions to the crystal packing, solution 13 C/ 1 H NMR chemical shifts, conformations, and NMR coupling constants. The phospho-rus-carbon coupling constants n J PC ( n = 2 and 3) in I and m J PC ( m = 1, 2, 3 and 4) in II were evaluated. For a comparative study, chiral analogous structures were retrieved from the Cambridge Structural Database (CSD) and their geometries and conformations are discussed.