The process consisting of reacting a (2,5'-anhydro-1-??-D-pentofuranosyl)uracil or (2,5'-anhydro-1-??-D-pentafuranosyl)-6-azauracil nucleoside, having the following structural formula: ##SPC2##wherein X is CH or N, M is a member selected from the group consisting of hydrogen, lower alkyl of from 1 to 4 carbon atoms, inclusive, hydroxy-lower alkyl of from 1 to 3 carbon atoms, inclusive, loweralkoxy