The present invention is directed to new nucleoside monophosphate derivatives of lipid ester residues of general formula (I) ##STR1## wherein R.sup.1 represents an optionally substituted alkyl chain having 1-20 carbon atoms;R.sup.2 represents hydrogen, an optionally substituted alkyl chain having 1-20 carbon atoms;R.sup.3, R.sup.4 and R.sup.5 represent hydrogen, hydroxy, azido, amino, cyano, or halogen;X represents a valence dash, oxygen, sulfur, a sulfinyl or sulfonyl group;Y represents a valence dash, an oxygen or sulfur atom;B represents a purine and/or pyrimidine base;with the proviso that at least one of the residues R.sup.3 or R.sup.5 is hydrogen;to their tautomers and their physiologically acceptable salts of inorganic and organic acids and/or bases, as well as to processes for their preparation, and to drugs containing said compounds.