The Step-Wise Synthesis of Oligomeric Phosphoramidates

In this study, the step-wise synthesis to a series of higher phosphoramidates was explored, affording compounds containing N−P−N, symmetric and asymmetric P−N−P and P−N−P−N−P linkages. Salt elimination and lithiation strategies were employed to create the new P−N bonds. It was found that the steric bulk and electronic contribution of the substituents on the P(V) centers were important factors to the success of the reactions. The oligomeric phosphoramidates were characterized by multinuclear NMR and IR spectroscopies as well as ESI mass spectrometry. A selection of the synthesized P−N oligomers were evaluated for their antimicrobial activity against E.coli, S.aureus, C.albicans, and A.fumigatus at varying concentrations. The results suggest their potential use as environmentally friendly fire retardants as the minimal inhibitory concentration (MIC) value for all the compounds was found to be >128 μM, indicating that the compounds do not have any detectable antimicrobial activity.