Methods and novel intermediates for the preparation of acyclic nucleoside derivatives of the formula: ##STR1## where one of R.sub.1 and R.sub.2 is an amino acid acyl group and the other of R.sub.1 and R.sub.2 is a --C(O)C.sub.3 -C.sub.21 saturated or monounsaturated, optionally substituted alkyl and R.sub.3 is OH or H; or a pharmaceutically acceptable salt thereof.