One-bond {sup 13}C-{sup 1}H spin-coupling constants in aldofuranosyl rings. Effect of conformation on coupling magnitude
- Univ. of Notre Dame, IN (United States)
- Purdue Univ., West Lafayette, IN (United States)
One-bond {sup 13}C-{sup 1}H spin-coupling constants ({sup 1}J{sub CH}) have been studied in the model furanose 2-deoxy-{beta}-D-glycero-tetrofuranose (1) as a function of ring geometry in order to assess their utility as conformational probes. Ab initio molecular orbital (MO) calculations were conducted on the ten envelope forms and the planar form of 1 using the second-order Moller Plesset (MP2) electron correlation treatment with a polarized split-valence (6.31 G*) basis set. The derived structures were used to compute {sup 1}J{sub CH} values in conformers of 1 at the Hartree-Fock and MP2 levels of theory which were subsequently sealed using a factor derived from accurate quadratic configuration interaction (QCISD) calculations. MO results indicate that C-H bond lengths in 1 vary with ring geometry, with a given C-H bond longest when quasi-axial and shortest when quasi-equatorial. Computed {sup 1}J{sub CH} values were found to be sensitive to C-H bond orientation, with greater coupling observed when a C-H bond is quasi-equatorial. Computations conducted on {beta}- D-ribofuranose (3) and 2-deoxy- {beta}-D-erythro-pentofurnaose (4) (HF/6-31G* level) show a C-H bond length/orientation dependence similar to that observed in 1. Experimental (NMR) data are presented which support the proposed correlation. These results suggest a role for {sup 1}J{sub CH} in the conformational analysis of furanose rings which may complement current methods based on {sup 3}J{sub HH}, {sup 3}J{sub CH}, and {sup 3}J{sub CH} values. 32 refs., 7 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 103544
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 33 Vol. 117; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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