solid-phase synthesis of 5-amino-1-β-D-ribofuranosylimidazole-4-carboxamide-5'-monophosphate (ZMP), a biosynthetic precursor of purine nucleotides, as well as a small collection of its 4-N-alkyl derivatives. The very difficult, direct, chemical phosphorylation of 5-amino-1-β-D-ribofuranosylimidazole-4-carboxamide (AICAR) was circumvented by installing a suitable, fully protected, phosphategroup on the