Syntheses of 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl‐β‐D‐altropyranose and of 1,6‐anhydro‐2‐0‐benzyl‐3,4‐0‐isopropylidene‐β‐D‐galactopyranose and their ring‐opening copolymerizations with 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl (or p‐methylbenzyl)‐β‐D‐glucopyranose

Abstract

The cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl‐β‐D‐altropyranose (TBLAT, M2) failed to give the fourth stereoregular 1,6‐α‐linked polysaccharide because of its very low homopolymerizability. However, the 1,6‐anhydro‐altrose monomer was found to copolymerize with 1,6‐anhydro‐2,3,4‐tri‐0‐(p‐methylbenzyl)‐β‐D‐glucopyranose (LGTXE, M1) with PF5 as catalyst at low temperature, giving highly stereoregular copolymers. The monomer reactivity ratios calculated by Kelen‐Tüdös method were r1 = 1.52 and r2 = 0.06. The differences in the reactivity between TBLAT monomer and other 1,6‐anhydro sugar derivatives are discussed. Moreover, 1,6‐anhy‐dro‐2‐0‐benzyl‐3,4‐0‐isopropylidene‐β‐D‐galactopyranose (ABIGA, M4), which showed no homopolymerizability under various conditions, was also copolymerized with 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl‐β‐D‐glucopyranose (LGTBE, M3) at low temperature. The monomer reactivity ratios of r3 = 2.2 and r4 = 0.0 indicate that in the copolymers every galactose unit distributed as a single unit through the main chain. The cause for the lower polymerizability of ABIGA is discussed. Hydrolysis of the copolymer with trifluoroacetic acid gave a copolymer in which only galactose units contained free hydroxyl groups, which were then methylated by methyl iodide. Stereoregular 1,6‐α‐linked galactoglucan composed of free sugar units was prepared by debenzylation of the ABIGA‐LGTBE copolymer followed by hydrolysis.

Synthesis of Altrose Poly-amido-saccharides with β-N-(1→2)-d-amide Linkages: A Right-Handed Helical Conformation Engineered in at the Monomer Level

“…As shown in Figure B, the value of k for the aminolysis reaction of 6 ( k = 1.09 × 10 –4 L·mol –1 ·s –1 ) is about one-fifth of that for the ring-opening reaction of 7 ( k = 5.42 × 10 –4 L·mol –1 ·s –1 ), indicating its relative lower ring-opening reactivity. This may be due to a smaller ring strain for the alt-lactam monomer compared to the glc-lactam monomer, as observed for 1,6-anhydro-2,3,4-tri- O -benzyl-β- d -altropyranose . Steric hin drance may also play an important role as the 5-benzyloxylmethyl group is oriented on the same face with the four-membered β-lactam ring.…”

“…This may be due to a smaller ring strain for the alt-lactam monomer compared to the glc-lactam monomer, as observed for 1,6anhydro-2,3,4-tri-O-benzyl-β-D-altropyranose. 84 Steric hin drance may also play an important role as the 5-benzyloxylmethyl group is oriented on the same face with the fourmembered β-lactam ring. However, the observed decrease in aminolysis rate for 6 in comparison to 7 does not necessarily preclude the successful polymerization of monomer 1.…”

Chemical synthesis of amino-group-containing (1 → 6)-α-D-glucan derivatives by ring-opening polymerization of 1,6-anhydroazido sugars

“…The polymerizations were carried out under high vacuum at low temperature in anhydrous methylene chloride with cationic catalysts as described previously. 21,26,31 In the polymerization with the Lewis acid-benzoyl fluoride complex as catalyst, the reaction of the Lewis acid and benzoyl fluoride was carried out in methylene chloride at the polymerization temperature for 30 min, and then the monomer solution in methylene chloride was added. The polymerization was terminated by the addition of a small amount of methanol.…”

Chemical synthesis of a new polysaccharide. Ring-opening polymerization of 1,6-anhydro-2,3,4-tri-O-benzyl-.beta.-D-allopyranose and preparation of stereoregular 1→ 6)-α-D-allopyranan

“…As the mole fraction of TBALL in the feed increased, the conversion decreased and the specific rotation of the "In chloroform. 6 In water, before freeze-drying.…”