In an effort to prepare novel inhibitors of VanX, N-[(1-aminoethyl)hydroxyphosphinyl]-D-alanine 1 and S-[(aminoethyl)hydroxyphosphinyl]-thiolacetic acid 2 were synthesized and evaluated as inhibitors of VanX. Phosphonamidate 1 was shown to be a partial competitive inhibitor of VanX with a Ki of 36+/-3 microM, and phosphothioate 2 was shown not to inhibit VanX.