Chemoenzymatic synthesis and antiviral evaluation of conformationally constrained and 3'-methyl-branched carbanucleosides using both enantiomers of the same building block. 
Starting from both enantiomers of a readily available building block, a straightforward enantioselective approach to constrained 3'-methyl-2',3'-alpha-oxirane-fused and 3'-methyl-3',4'-alpha-oxirane-fused carbanucleosides bearing different purine base analogues is described.  The title compounds were evaluated as potential antiviral agents against important viruses.  None of the new compounds had significant antiviral activity at a concentration of 100 microg/mL, which was the highest concentration tested.