A new class of 2,10-dichloro-6-substituted amino acid ester-12H-dibenzo[d,g][1,3,2]dioxaphosphocin-6-oxides have been synthesized in good yields via the condensation of 2,10-dichloro-6-chloro-12H-dibenzo[d,g][1,3,2]dioxaphosphocin with various amino acid esters in the presence of triethylamine. The title compounds were characterized by elemental analysis, IRS, NMR (H-1, C-13 and P-31) and mass spectral studies and found to exhibit moderate antimicrobial activity.