Abstract Analogues of the antivirals (2S)-9-(3-hydroxy-2-phosphonylmethoxypropyl) adenine (Ia) and 9-(2-phosphonylmethoxyethyl) adenine (Ib), modified in the alkyl chain, are described. The phosphonylmethoxyalkyl derivatives were prepared by condensation of sodium alkoxides of hydroxyalkyladenines (or their N-protected derivatives) with dimethyl p- toluenesulfonyloxymethanephosphonate (II) followed by alkaline hydrolysis and reactions ...