The invention relates to compounds of general formula (I); in which R is an amino or guanidino group; R.sup.2 is acetyl or trifluoroacetyl; X is CONH, NHCO or O; n is an integer from 2 to 6; and Y is C.sub.2 C.sub.8 alkyl C.sub.3-8 cycloalkyl, C.sub.1 C.sub.4 alkoxyalkyl, an amino acid or dipeptide, or a pharmaceutically acceptable derivative thereof, methods for their preparation, pharmaceutical formulations containing them or their use in the prevention or treatment of a viral infection ##STR00001##