Phosphate derivatives of substituted butyl guanines, antiviral compositions containing them, and methods of treating viral infections with them

A compound of the formula:

• ##STR27## wherein R.sup.1 is hydroxy, amino or halogen;
• and R.sup.2 and R.sup.3 are independently selected from hydrogen and a phosphate group having the formula:
• ##STR28## provided that R.sup.2 and R.sup.3 are not concurrently hydrogen, or R.sup.2 and R.sup.3 taken together form a phosphate group having the formula:
• ##STR29## wherein R.sup.4 and R.sup.5 are independently selected from hydrogen, a pharmaceutically-acceptable cation, alkyl having 1 to 6 carbon atoms, phenyl or phenylalkyl wherein the alkyl moiety has 1 to 6 carbon atoms.