Sensitivity of 1JC1-H1 magnitudes to anomeric stereochemistry in 2,3-anhydro-O-furanosides

Article abstract of DOI:10.1021/jo001747a

The magnitude of the one-bond coupling constant between C₁ and H₁ 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, ¹J_C1-H1 = 163 - 168 Hz; and when this hydrogen is cis to the oxirane ring, ¹J_C1-H1 = 171 - 174 Hz. In contrast, for 2,3-anyhdro-S-glycosides, the size of the ¹J_C1-H1 is not sensitive to C₁ stereochemistry. Computational studies on all four methyl 2,3-anhydro-O-furanosides (5-8) demonstrated that ¹J_C1-H1 was inversely proportional to the length of the C₁-H₁ bond. A previously reported equation, which relates C₁-H₁ bond distance and atomic charges to ¹J_C1-H1 magnitudes, could be used to accurately predict the J values in the α-lyxo (5) and β-ribo (8) isomers. In contrast, with the β-lyxo (6) and α-ribo isomers (7), this equation underestimated the size of these coupling constants by 10-20 Hz.