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Synthesis of a β-(1→6)-linked polysaccharide via ring-opening polymerization with neighboring-group participation

✍ Scribed by Haruo Ichikawa; Kazukiyo Kobayashi; Hiroshi Sumitomo; Conrad Schuerch

Publisher
Elsevier Science
Year
1988
Tongue
English
Weight
379 KB
Volume
179
Category
Article
ISSN
0008-6215

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✦ Synopsis

l-+6)-P-D-Galactopyranan was synthesized by cationic ring-opening polymerization of 1,6-anhydro-2-O-benzoyl-3,4-di-O-henzyl-P-D-galactopyranose and subsequent deprotection.

The polymerization proceeded at 0" and 20", using 10-50 mol% of phosphorus pentafluoride as initiator in dichloromethane, to give the polymer of %, 2.63.6

x 103. The benzyl and benzoyl groups were removed by using sodium in liquid ammonia and an exclusively (l-+6)-linked /3-D-galactopyranan oligosaccharide of average d.p. 7 was obtained.

The formation of the p-(1*6)linkage was explained by a neighbouring-group effect on the steric control of the propagation step: BzO-2 in the growing terminal unit reacted with the cyclic trialkyloxonium ion to form a stable dioxacarbenium (dioxolenium) ion, which allowed exclusive P-side attack of the incoming monomer.

📜 SIMILAR VOLUMES

Ring-opening polymerization and copolyme
Ring-opening polymerization and copolymerization of a new benzylated 1,6-anhydro-3-azido-3-deoxy-β-D-allopyranose and synthesis of amino-polysaccharides with 1,6-α-allopyranosidic structure
✍ Kazuyuki Hattori; Takashi Yoshida; Toshiyuki Uryu 📂 Article 📅 1997 🏛 John Wiley and Sons 🌐 English ⚖ 548 KB

## Abstract Ring‐opening polymerization of a new anhydro‐hexose monomer having an azido group, 1,6‐anhydro‐3‐azido‐2,4‐di‐__O__‐benzyl‐3‐deoxy‐β‐D‐allopyranose (A3ABA), was carried out with Lewis acid catalysts to give a stereoregular (1→6)‐α‐D‐allopyranan derivative having the azido group at the C