Treatment of racemic diisopropyl [1,3-bis(mesyloxy)propyl]phosphonate with allyl-, benzyl-, 2-hydroxyethyl-, or propylamine gave the corresponding diisopropyl [(3-(alkylamino)-1-(mesyloxy)propyl]phosphonates. Heating of their toluene solution with aqueous potassium carbonate effected a cyclization to diisopropyl (1-alkylazetidin-2-yl)phosphonates. In the 1-benzyl- and [1-(2-hydroxyethyl)azetidin-2-yl]phosphonate, the isopropyl ester groups were removed by treatment with bromotrimethylsilane which gave 1-benzyl- and [1-(2-hydroxyethyl)azetidin-2-yl]phosphonic acid. Following hydrogenolysis of the benzyl group afforded azetidin-2-ylphosphonic acid.