Abstract CycloSal-nucleosyl-phosphate triesters are a known class of highly effective nucleotide prodrugs (pronucleotides) of antivirally active nucleoside analogues. Until recently, the synthesis of these compounds always gave diastereoisomeric mixtures. Then, a convergent route for the stereospecific synthesis of cycloSal-triesters was described to give isomerically pure cycloSal-prodrugs for the treatment of viral diseases. Here, the ...