Abstract: The L-monovaline ester derived from 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol and its pharmaceutically acceptable salts are of value as antiviral agents with improved absorption.

Abstract: The L-monovaline ester derived from 2-(2-amino-1,6-dihydro-6-oxo-purin-9-yl)methoxy-1,3-propanediol and its pharmaceutically acceptable salts are of value as antiviral agents with improved absorption.

Abstract: Compounds of the Formula I ##STR1## wherein X is hydrogen, chloro, amino or hydroxy; R.sup.1 is an achiral amino acid acyl residue with a tertiary .alpha.-carbon atom. Preferred achiral amino acid acyl residues have the formula ##STR2## wherein each R.sup.2 is alkyl with 1 to 6 carbon atoms, cycloalkyl with 3 to 5 carbon atoms, or benzyl; or the two R.sup.2 groups link together to form a polymethylene group with 3 to 9 carbon atoms, and pharmaceutically acceptable salts thereof are antiviral agents with improved absorption. Intermediates for the preparation of the compounds of Formula I are also described.