Starting from phthalimidoalkanoylamines 1 (amino-protected derivatives of L-alanine, L-valine, and L-leucine), we have suggested a straightforward synthetic route to 5-amino-1,3-oxazol-4-ylphosphonic acid derivatives 5 containing a chiral aminoalkyl substituent on the 2-position of the oxazole ring. Compounds 5 have been further used to obtain phosphonodipeptides 8, 9, and 10 with the original optical purity retained.