Nucleotide analogues having the general formula (I) and pharmaceutically acceptable derivatives: ##STR1## wherein n is 0 or an integer; X is O or S, CH.sub.2, CH-halogen, CH--N.sub.3, or C.dbd.CH.sub.2 ;Q and U are independently selected from: O, S, and CH(R.sub.a) wherein R.sub.a is hydrogen, OH, halogen, N.sub.3, NH.sub.2, SH, carboxyl, C.sub.1-6 alkyl or R.sub.a is CH.sub.2 (R.sub.b) wherein R.sub.b is hydrogen, OH, SH, NH.sub.2, C.sub.1-6 alkyl or carboxyl; or both Q and U are CH when Q and U are linked by a double bond;Z is selected from: O, a C.sub.1-6 alkoxy, a C.sub.1-6 thioalkyl, a C.sub.1-6 aminoalkyl, (CH.sub.2).sub.m wherein m is 0 or an integer, and N(R.sub.c).sub.2 wherein both R.sub.c are independently hydrogen or a C.sub.1-6 alkyl; andR2 is a purine or pyrimidine base or an analogue or derivative thereof. Members of this series of analogues possess anti-viral activity.