An efficient two-step procedure for the synthesis of pyrimidine nucleosides was developed. A series of glycosyl 5-(aminomethylene)-1,3-dioxane-4,6-dione derivatives were prepared from B-aldofuranosyl isonitriles by reaction with Meldrum’s acid or by allowing ami-nomethylene Meldrum's acid to react with labile 1-aldofuranosyl. The resultant 5-(aminomethylene)-1,3-dioxane-4,6-dione derivatives underwent reaction with benzyl isocy-anate or 2,4-dimethoxybenzyl isocyanate via a transesterification to provide uridine-5-carboxylic acid derivatives and related nucleosides. These nucleoside carboxylic acids were converted into other C-5 derivatives by halo-decarboxylation with N-bromosucciminide. Wherever applicable, deprotection of the N-benzyl imide was performed using TFA and the glycosyl ester protecting groups were saponificated with K2CO3 in MeOH.