Relationship of ¹³C to Vicinal ¹H Coupling to the Torsion Angle in Uridine and Related Structures

Abstract

Uracil was prepared enriched at C2 with carbon-13 and converted into uridine from which 2,5′-anhydro-1-β-D-ribo-furanosyl and 2,2′-anhydro-1-β-D-arabino-furanosyl uracil were prepared. The 13C2 to vicinal proton coupling constants for these compounds were measured and are compared in terms of the expected torsion angles defined by the two atoms. The evidence suggests the existence of a Karplus-type relationship as is found for vicinal proton coupling. The data establish the anti conformation for uridine in solution.

Structural Features of Dinoflagellate Toxins Underlying Biological Activity as Viewed by NMR

“…These conditions have led to the invention of a new method called ''Jbased configuration analysis'' for assigning the relative configuration of acyclic structures in natural products. 12,47,48 Vicinal carbon-proton spin-coupling constants ( 3 J C,H ) show Karplustype dihedral dependence [49][50][51] (Fig. 4); applications of 2;3 J C,H to conformational analyses and/or stereospecific assignments of methylene protons have been reported for proteins, [52][53][54] carbohydrates, 55,56 and polynucleotides.…”

Isotopically-enriched carbohydrates: The preparation of [2H]-enriched aldoses by catalytic hydrogenolysis of cyanohydrins with 2H2

“…native approach has been to analyze 13C-enriched compounds by 'Hmr (28)(29)(30)(31)(32)(33)(34). In cases where 'Hmr spectra are complex, the synthesis of compounds with 'H-and (or) 13C-enrichment may aid interpretation.…”

The crystal and molecular structures of 2,2'-anhydro-1-β-D-arabino-furanosyl uracil

“…In order to demonstrate a Karplus (1959) type relationship between 13C-vicinal-~H coupling constants and the corresponding torsional angles in solution n.m.r, spectroscopy, Lemieux, Nagabhushan & Paul (1972) examined the spectra of uridine and other related compounds that had the 2 position of the uracil ring enriched with a3C. They were able to show that an approximate Karplus relation indeed exists, but the torsional angles they used were only roughly determined from molecular models.…”