STRUCTURE OF THE PRODUCT FROM A NOVEL CYCLIZATION REACTION INVOLVING A C(6)-SUBSTITUTED URIDINE ANALOG

5,6,7,7a,9,10,14b,14c-Octahydro-4-[2,3-O-(1-methylethylidene)-beta-D-ribofuranosyl]cyclopenta-[4,5]pyrimido[5',4':3,4]pyrrolo[2,1-alisoquinoline-1,3(2H,4H)-dione, C25H31N3O6, M(r) = 469.54, tetragonal, P4(3)2(1)2, a = 12.577 (2), b = 12.577 (2), c = 29.893 (4) angstrom, V = 4729 (1) angstrom3, Z = 8, D(x) = 1.319 g cm-3, lambda(Cu Kalpha) = 1,5418 angstrom, mu = 7.9 cm-1, F(000) = 2000, T = 298 K, final R = 0.038, wR = 0.064 for all 1884 independent reflections and 432 variables. The crystal structure shows a syn conformation around the N(1)-C(1') single bond, consistent with other C(6)-substituted uridine analogs, and an unusual O(1') endo conformation of the ribose ring. The stereochemistries of the three newly created chiral centers are 14cR, 4aR, 7aS.