Crystal structure and conformation of 2 '-C-ethoxy-3 ',5 '-O-(tetraisopropyldisiloxane-1,3-diyl)uridine

The title compound, C23H42N2O8Si2, Mr=530.77, crystallizes in the monoclini c system, space group P2(1), with a=10.577(5), b=10.528(2), c=13.374(5)Angs trom, beta =100.63(3)degrees, V=1461(2)Angstrom (3), Z=2, D-x=1.207g/cm(3), lambda (MoK alpha)=0.71073 Angstrom, mu =1.590mm-1, T=299+/-1K, F(000)=572 , R=0.070 and R-w=0.075 for 1232 observed reflections with I greater than o r equal to3 sigma (I). The analysis result indicates that the configuration of the title compound at C(2') is S. In the crystal state the molecule has anti-conformation about glycosidic bond with the torsion angle -126.96 deg rees. The sugar ring is puckered with C3'-endo-C4'-exo, and the conformatio n of the C(4')-C(5') bond is +SC.