Isopropyl 3‐deoxy‐α‐d‐ribo‐hexopyranoside (isopropyl 3‐deoxy‐α‐d‐glucopyranoside): evaluating trends in structural parameters

Isopropyl 3‐deoxy‐α‐d‐ribo‐hexopyranoside (isopropyl 3‐deoxy‐α‐d‐glucopyranoside), C9H18O5, (I), crystallizes from a methanol–ethyl acetate solvent mixture at room temperature in a 4C1 chair conformation that is slightly distorted towards the C5SC1 twist‐boat form. A comparison of the structural parameters in (I), methyl α‐d‐glucopyranoside, (II), α‐d‐glucopyranosyl‐(1→4)‐d‐glucitol (maltitol), (III), and 3‐deoxy‐α‐d‐ribo‐hexopyranose (3‐deoxy‐α‐d‐glucopyranose), (IV), shows that most endocyclic and exocyclic bond lengths, valence bond angles and torsion angles in the aldohexopyranosyl rings are more affected by anomeric configuration, aglycone structure and/or the conformation of exocyclic substituents, such as hydroxymethyl groups, than by monodeoxygenation at C3. The structural effects observed in the crystal structures of (I)–(IV) were confirmed though density functional theory (DFT) calculations in computed structures (I)c–(IV)c. Exocyclic hydroxymethyl groups adopt the gauche–gauche (gg) conformation (H5 anti to O6) in (I) and (III), and the gauche–trans (gt) conformation (C4 anti to O6) in (II) and (IV). The O‐glycoside linkage conformations in (I) and (III) resemble those observed in disaccharides containing β‐(1→4) linkages. The X‐ray crystal structure of isopropyl 3‐deoxy‐α‐d‐ribo‐hexopyranoside (isopropyl 3‐deoxy‐α‐d‐glucopyranoside) was determined and compared to the structures obtained previously for three related compounds. Density functional theory (DFT) calculations were used to validate the trends observed in bond lengths, angles and torsion angles in these structures.