Synthesis and properties of methanesulfonyl derivatives of diethyl esters of 5-(hydroxyalkylamino)-1,3-oxazol-4-yl-phosphonic acids

A number of {[4-(diethoxyphosphoryl)-2-R-1,3-oxazol-5-yl]amino}alkyl methanesulfonates were synthesized and the peculiarities of their reaction with triethylamine were studied. The influence of the structure of the 5-alkanolamine substituent on the efficiency of their transformation into 7-R-1-ethoxy-5-methyl-1,3,4,5-tetrahydro-1λ⁵-[1,3]oxazolo[4,5-c][1,5,2]oxazaphosphepine-1-ones was clarified. The structure of the [1,3]oxazolo[4,5-c][1,5,2]oxazaphosphepine derivatives has been reliably proven by elemental analysis, IR, ¹H, ¹³C, and ³¹P NMR spectroscopy (including 1D and 2D experiments), mass spectrometry and single crystal X-ray diffraction. The oxazole cycle in [1,3]oxazolo[4,5-c][1,5,2]oxazaphosphepines is easily cleaved by water in an acidic environment, which leads to the formation of derivatives of the new heterocyclic system – N-(2-ethoxy-5-methyl-2-oxido-4-oxo-1,5,2-oxazaphosphepan-3-yl)arylamides.