Solution and Solid State Structure of 2′,5′-BIS-(O-Trityl)-3′-Oximinouridine

Comparison of the solution (in CDCl3 at 500 MHz H-1 NMR) and X-ray crystal studies of 3'-oximinouridine 1 shows in general good agreement with the high anti glycosidic angle and in the conformation about C4'-C5'. The sugar pucker (C2'-endo) is qualititatively identical in both cases. This is the first example of a conformationally sugar-rigid nucleoside in which the rigidity arises from the sp2 character of an endocyclic carbon (i.e. C3'), not from the strain due to the ring fusion (see ref. 7 for conformationally strained nucleosides).