Four D??altritol nucleosides with a 3′??O??tert??butyldimethylsilyl protecting group are synthesized (base moieties are adenine, guanine, thymine and 5??methylcytosine). The nucleosides are obtained by ring opening reaction of 1, 5: 2, 3??dianhydro??4, 6??O?? benzylidene??D??allitol. Optimal reaction circumstances (NaH, LiH, DBU, phase transfer, microwave irridation) for the introduction of the heterocycles are base??specific. For the ...