Hemicarbasucrose: Turning off the Exoanomeric Effect Induces Less Flexibility

Abstract

Hemicarbasucrose, a close congener of sucrose in which the endocyclic oxygen atom of the glucose moiety is replaced by a methylene group was synthesized for the first time. The conformational behaviour of hemicarbasucrose was studied by a combination of molecular mechanics and NMR spectroscopy (J and NOE data). It was shown that the carbadisaccharide populates two distinct conformational families in solution, the normal syn-psi conformation, which is the predominating conformation of the parent natural O-glycoside, and the anti-psi conformation, which has not been detected for the O-disaccharide. Interestingly, the hemicarbasucrose is less flexible than its natural congener.

Conformational Plasticity in Glycomimetics: Fluorocarbamethyl‐L‐idopyranosides Mimic the Intrinsic Dynamic Behaviour of Natural Idose Rings

“…[12] For instance, for carbasugars, for which the ring oxygen hasb een replaced by am ethylene group, [13] this substitution rules out the anomeric effects, modifies the intramolecularh ydrogen-bond pattern, modulates the amphiphilicity of the sugar ring, and results in changes in the flexibility and conformations population distributions. [14] Fluorine is not an endogenous nucleus, but medicinal chemistry studies have demonstrated its useful introductioni n bioactive substances to improve their pharmacokinetics properties and to modulate its biological properties. From the NMR perspective, the presence of 19 Fa toms may also deliver important conformational ands tructurali nformation,c omplementary to that provided by 1 Ha nd 13 Cnuclei.…”

Fluoro‐Carba‐Sugars are Glycomimetic Activators of the glmS Ribozyme

“…The α‐ d ‐glucose isomer 12 , with the inverted configuration at C5, was not accessible from 11 through isomerization of the corresponding aldehyde at C5 because of a rapid loss of fluorine during the isomerization step (results not shown) . Therefore, we developed an alternative synthetic route comprising epoxidation of the olefin and subsequent regioselective epoxide opening.…”

Synthesis of carbasugar-containing non-glycosidically linked pseudodisaccharides and higher pseudooligosaccharides

“…83 C-6-Deprotected carbaidopyranosides have been converted to carbaglucopyranosides by an oxidation-epimerisation-reduction sequence, although this has only been shown on a glycosidically linked pseudodisaccharide (285?286) as yet (Scheme 14). 84 Treatment of the exo-glycal rearrangement precursors with trimethylaluminium instead of TIBAL gave a rearrangement to cyclohexane products with no debenzylation observed. 85 Here though, a methyl group was added from the reagent (rather than a hydride from TIBAL), giving a carbahexopyranose (287), again with stereoselectivity for the C-1-axial product (Scheme 15).…”