Diastereomers ( R C , S P )‐ and ( R C , R P )‐ S ‐methyl P ‐(3‐azidopropyl)‐ N ‐[(1 R )‐1‐phenylethyl]phosphonamidothioate

Diastereoisomers of the title organophosphorus compound, C 12 H 19 N 4 OPS, denoted R C S P , (I), and R C R P , (II), were structurally characterized and compared. Asymmetric phosphorus compounds are of interest with regard to the use of these systems as possible protein probes via the stereoselective delivery of an azide group tethered to the P atom into key protein regions. The diastereomers were produced in a 1:1 mixture and isolated by chromatography. Although both isomers crystallize in the same space group with superficially similar cell constants, conformational and packing differences are pronounced. Despite the conformational differences, strong intermolecular hydrogen bonding links both isomers into chains parallel to the a axis [N...O = 2.8609 (18) and 2.966 (3) Å in (I) and (II), respectively], with C—H...π interchain interactions of ca 3.5 Å.