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  • Completely β-selective glycosylation using 3,6-O-(o-xylylene)-bridged axial-rich glucosyl fluoride.

Completely β-selective glycosylation using 3,6-O-(o-xylylene)-bridged axial-rich glucosyl fluoride.

Journal of the American Chemical Society (2012-04-06)
Yasunori Okada, Noriaki Asakura, Masafumi Bando, Yoshiki Ashikaga, Hidetoshi Yamada
ABSTRACT

A completely β-selective glycosylation that does not rely on neighboring group participation is described. The novelty of this work is the design of the glycosyl donor locked into the axial-rich form by the o-xylylene bridge between the 3-O and 6-O of d-glucopyranose. The synthesized 2,4-di-O-benzyl-3,6-O-(o-xylyene)glucopyranosyl fluoride could efficiently react with various alcohols in a SnCl(2)-AgB(C(6)F(5))(4) catalytic system. The mechanism composed of the glycosylation and isomerization cycles was revealed through comparative experiments using acidic and basic molecular sieves. The achieved perfect stereocontrol is attributed to the synergy of the axial-rich conformation and convergent isomerization caused by HB(C(6)F(5))(4) generated in situ.

MATERIALS
Product Number
Brand
Product Description

Supelco
o-Xylene solution, certified reference material, 5000 μg/mL in methanol
Sigma-Aldrich
o-Xylene, anhydrous, 97%
Supelco
o-Xylene, analytical standard
Supelco
o-Xylene, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Xylenes, reagent grade
Sigma-Aldrich
Xylenes, ACS reagent, ≥98.5% xylenes + ethylbenzene basis
Sigma-Aldrich
o-Xylene, reagent grade, ≥98.0%
Sigma-Aldrich
Xylenes
Sigma-Aldrich
o-Xylene, puriss. p.a., ≥99.0% (GC)
Sigma-Aldrich
Xylenes, histological grade
Supelco
o-Xylene, suitable for HPLC, 98%