Two new chiral nucleoside analogues:: (4R,5R)-4-(4,6-dimethylpyrimidin-2-ylsulfanyl)-5-[(2S,5R)-2-isopropyl-5-methylcyclohexyloxy]-2,3,4,5-tetrahydrofuran-2-one and (4R,5R)5-[(2S,5R)-isopropyl-5-methylcyclo-hexyloxy]-4-(4-methyl-1,3-thiazol-2-ylamino)-2,3,4,5-tetrahydrofuran-2-one

Synthesis and X- ray structural investigations have been carried out for the two title compounds, viz. C20H30N2O3S, ( I), and C18H28N2O3S, ( II). In both molecules, the cyclohexyloxy moiety and the conjugated cyclic system are located on opposite sides of the tetrahydrofuran- 2- one ring. In the crystal structure of ( II), there are two types of intermolecular hydrogen bonds, viz. C - H center dot center dot center dot S and N - H center dot center dot center dot O, and the molecules form a three- dimensional supramolecular architecture via the hydrogen bonds.