From Tri‐O‐Acetyl‐D‐Glucal to (2R,3R,5R)‐2,3‐Diazido‐5‐Hydroxycyclohexanone Oxime

Synthesis and geometry of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-α/β-d-arabino- and -α/β-d-ribo-hexopyranosid)uronates

“…These findings are surprising, because other methyl 4-O-acetyl-3-azido-2,3-dideoxyhexopyranosides with the D D-ribo configuration, which we previously reported, adopted the 4 C 1 conformation in solution. 20,24 This means that the 5-COOMe group, unlike the 5-CH 2 X group (X = OH, OAc, OTs, I), influences the conformational preferences of the pyranose ring. What is the reason for this difference?…”

Synthesis and conformational analysis of methyl 3-amino-2,3-dideoxyhexopyranosiduronic acids, new sugar amino acids, and their diglycotides

“…Nevertheless, methyl 3-azido-2,3-dideoxyhexopyranosides with the D D-ribo configuration, on which we reported earlier, which are analogous to the compounds discussed in this paper, always adopted the 4 C 1 conformation in solution. 27,28 This means that, unlike the 5-CH 2 X group (X = OH, OAc, OTs, I), the 5-COOR group (R = H, Me), does influence the conformational preferences of the pyranose ring. What is the reason for this difference?…”

Methyl 4-O-Acetyl-3-azido- and 3-Azido-4-O-methylsulfonyl-2,3,6,-trideoxyhex-5- enopyranosides in DFT-Level Conformational Studies

“…With regard to O-acetyl derivatives (1, 3, 4), these findings agree with our previously reported results based on 1 H NMR analysis. 29,30 The 1 H NMR spectra indicate beyond any doubt that 1 and 4 adopt the 4 C 1 and 1 C 4 conformations, respectively, in CDCl 3 solution. The 4 C 1 conformation is optimal for 1 because the 3-N 3 group is equatorially oriented and the anomeric effect is favorable (without a 1,3-diaxial interaction between the 1-OMe and 3-N 3 groups).…”

“…29,30 The latter always adopt the 4 C 1 conformation in solution, but the former adopt the 4 C 1 or 1 C 4 conformation or remain in 4 C 1 a 1 C 4 conformational equilibrium, depending on the configuration of the C1, C3, and C4 carbon atoms.…”

“…Our previous findings, based on 1 H NMR spectra, indicate that an exocyclic double bond introduced onto the C5 carbon atom causes the conformations of 3-azido-2,3,6-trideoxyhex-5-enopyranosides to become much more flexible in comparison with those of 3-azido-2,3-dideoxyhexopyranosides or 3-azido-6-iodo-2,3,6-trideoxyhexopyranosides. 29,30 The latter always adopt the 4 C 1 conformation in solution, but the former adopt the 4 C 1 or 1 C 4 conformation or remain in 4 C 1 a 1 C 4 conformational equilibrium, depending on the configuration of the C1, C3, and C4 carbon atoms.…”