Stereoselective introduction of fluorine in carbohydrates with and in anhydrous hydrogen fluoride systems

Miethchen, Ralf; Gabriel, T.; Kolp, G.; Peters, D.

doi:10.1016/s0022-1139(00)83699-4

Cited by 1 publication

(3 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to Ziegler et al , the reaction of 5 with KHF 2 as the source of fluoride stereoselectively yields β-mannosyl fluoride 6β . However, both our and Ziegler’s 13 C NMR data matched those of Miethchen and Kolp 25 for the α-anomer 6α . Miethchen reported that reaction with Et 3 N·3HF as the fluoride source proceeds predominantly via neighbouring group participation (NGP) through which a transient acyloxonium ion shields the β-face of the ring to generate α-mannosyl fluoride 6α .…”

Section: Table 1 13 C– 19 F...supporting

confidence: 86%

“…62%). 25 Conveniently, we were able to spectroscopically diagnose the anomeric configuration of 6β with NOESY experiments (spectra in Supporting Information). We also highlight that the 2 J C2,F coupling constant measured for 6β (20 Hz) was consistent both with the value calculated for 7β by DFT methods (17 Hz; Table 1 ) and with that reported by Bock and Pedersen.…”

Section: Table 1 13 C– 19 F...mentioning

confidence: 99%

“…In the absence of β-stereo-directing structural features and conditions, these compounds are kinetically and thermodynamically disfavoured to their α-configured congeners. The use of a participating O -acyl group at C-2 also erodes β-stereoselectivity; 25 however, the importance of benzoyloxy groups to l -hexose selectivity 17 and their inherent compatibility with all chemistries in the scheme is once more emphasised.…”

Section: Table 1 13 C– 19 F...mentioning

confidence: 99%

See 2 more Smart Citations

C-5 Epimerisation of d-Mannopyranosyl Fluorides: The Influence of Anomeric Configuration on Radical Reactivity

Ferro,

See,

Pierens

et al. 2023

Synthesis

View full text Add to dashboard Cite

The fluorine-directing effect has so far been exploited to provide short and efficient synthetic routes to rare L-ido sugars. However, the importance of anomeric configuration to its success has remained experimentally unverified. We now report on the synthesis of α- and β-configured per-O-benzoylated mannopyranosyl fluorides and initially show that their reactivity towards photo-bromination is strongly dependent on the anomeric configuration. The stereochemical basis of the fluorine-directing effect is then validated by revealing the striking difference in stereoselectivity observed for the free radical reductions of the isolated 5-C-bromo sugars. This work importantly provides a synthetic route to a donor-functionalised derivative of L-gulose and reveals new insights into the behaviour of glycosyl radicals.

show abstract

Section: Table 1 13 C– 19 F...supporting

confidence: 86%

Section: Table 1 13 C– 19 F...mentioning

confidence: 99%