Sensitivity of (1)J[C(1)-H(1)] magnitudes to anomeric stereochemistry in 2,3-anhydro-O-furanosides.
The magnitude of the one-bond coupling constant between C(1) and H(1) in 2,3-anhydro-O-furanosides has been shown to be sensitive to the stereochemistry at the anomeric center. A panel of 24 compounds was studied and in cases where the anomeric hydrogen is trans to the epoxide moiety, (1)J[C(1)-H(1)] = 163-168 Hz; and when this hydrogen is cis to the oxirane ring, ((1)J[C(1)-H(1)] = 171-174 Hz. In contrast, for 2,3-anhydro-S-glycosides, the size of the (1)J[C(1)-H(1)] is not sensitive to C(1) stereochemistry. Computational studies on all four methyl 2,3-anhydro-O-furanosides (5-8) demonstrated that (1)J[C(1)-H(1)] was inversely proportional to the length of the C(1)-H(1) bond. A previously reported equation, which relates C(1)-H(1) bond distance and atomic charges to (1)J[C(1)-H(1)] magnitudes, could be used to accurately predict the J values in the alpha-lyxo (5) and beta-ribo (8) isomers. In contrast, with the beta-lyxo (6) and alpha-ribo isomers (7), this equation underestimated the size of these coupling constants by 10-20 Hz.
Callam
C S
CS
Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA.
Gadikota
R R
RR
Lowary
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TL
D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation; D009005:Monosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D013223:Statistics as Topic; D013865:Thioglycosides / Q000138:chemical synthesis* / Q000737:chemistry
D005663:Furans; D009005:Monosaccharides; D013865:Thioglycosides