Bifunctional Building Blocks for Glyco-Architectures by TiCl₄-Promoted Ring Opening of Cyclodextrin Derivatives

Abstract

During our studies on the preparation of blocklike substituted 1,4-glucans by cationic ring-opening polymerization,1,2 we found that TiCl4 behaves differently from common initiators like Et3O+X- (X = PF6, SbCl6), BF3.Et2O, or methyl triflate, causing only ring opening under formation of alpha-maltooligosyl chlorides bearing one free hydroxyl group (4-OH) at the nonreducing end. These compounds are valuable building blocks for the preparation of new glyco-architectures since they are easily accessible starting materials for direct glycosylations or the preparation of a variety of oligomeric glycosyl donors like alkyl glycosides, thioglycosides, or azides. We successfully carried out and optimized the TiCl4-promoted ring opening with per-O-methylated, per-O-ethylated, and temporarily protected per-O-allylated cyclodextrins of various ring size. 1H NMR spectroscopy and high-pressure liquid chromatography-evaporative light-scattering detection (HPLC-ELSD) were used to characterize the products.

Clustering of Escherichia coli Type‐1 Fimbrial Adhesins by Using Multimeric Heptyl α‐D‐Mannoside Probes with a Carbohydrate Core

“…[33] Subsequent per-acetylation with acetic anhydride and per-benzoylation with benzoyl bromide followed by nucleophilic substitution with sodium azide allowed isolation of the compounds 8 and 9, respectively. [34] Several methodologies are reported to form the linear malto-oligosaccharide from the corresponding CDs with Lewis or Brønsted acids such as H 2 SO 4 /Ac 2 O, [35] FeCl 3 / Ac 2 O, [36] ZnBr 2 /PhSSiMe 3 , [37] HClO 4 /Ac 2 O, [38,39] TiCl 4 , or BF 3 /MeOCH 2 CO 2 H. [40] These different protocols were evaluated on the acetylated derivative 8 without any success. The expected linear heptasaccharide was only formed with H 2 SO 4 /Ac 2 O [35] and in a low yield (less than 10 %) due to the formation of shorter linear oligomers by a depolymerization process.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2007–2008

“…Reagent remnants could be removed by ultrafiltration ready for MALDI (Shimizu, et al, 2007) Oligosaccharides TOF By TiCl 4 -promoted ring opening of cyclodextrin derivatives (Bösch & Mischnick, 2007) Oligosaccharides, glycolipids MALDI Gold(I)-catalyzed glycosylation of 1,2-anhydrosugars gives increased yields (Li, et al, 2008h) Proteoglycan core structures TOF/TOF (DHB) Synthesis from 1,6-anhydro-β-lactose (Shimawaki, et al, 2007) Sialylated oligosaccharides TOF (CHCA)…”

Ring-Opening of Cyclodextrins: An Efficient Route to Pure Maltohexa-, Hepta-, and Octaoses

“…Bosch et al [42] performed the CD ring-opening in a freshly prepared solution of Scheme 12. Regioselective opening of the corresponding perbenzoylated CD followed by their in situ glycosylation with various nucleophiles.…”