Substituent Effects of the Orthoester Group on Ring-Opening Polymerization of α-d-Glucopyranose 1,2,4-Orthoester Derivatives

Abstract

The first chemical synthesis of cellulose derivatives, (1→4)-β-d-glucopyranan derivatives has been accomplished by cationic ring-opening polymerization using 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthopivalate (1) as a starting monomer, taking into account substituent effects. Here, three orthoester derivatives as starting materials for the polymerization, 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthopropionate (2), 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthoacetate (3), and 3,6-di-O-benzyl-α-d-glucopyranose 1,2,4-orthobenzoate (4), were selected to investigate the substituent effects of orthoester group on the ring-opening polymerization. These three monomers were polymerized under the same reaction conditions as those of monomer 1, yielding stereoregular (1→4)-β-d-glucopyranan derivatives, previously reported. As the result, monomers 2−4 gave non-regioregular polymers consisting of (1→4)- and (1→2)-β-pyranose units, although they gave high stereoregularity, i.e., β-glucosidic linkage. Thus, it was concluded from the polymerizations of the monomers 1−4 that the orthopivaloyl group of the starting monomer is indispensable for regiospecificity of the polymerization, yielding only the (1→4)-glycosidic bond, not the (1→2)-bond.

Ring-Opening Polymerization of 3-O-Benzyl-β-l-arabinofuranose 1,2,5-Orthopivalate and Synthesis of Stereoregular (1→5)-α-l-Arabinofuranan

“…This (1→5)-α- l -arabinofuranan derivative has a good possibility of synthesizing regiospecifically branched arabinofuranan, owing to the ready distinction between C2- and C3-positions. Moreover, the ring-opening polymerization may give the polymer with higher molecular weight than that of the polymer by the polycondensation by Backnowsky et al, because the enhancement of polymerizability by the 3- O -benzyl group is expected from our earlier results. − …”

“…Moreover, the ring-opening polymerization may give the polymer with higher molecular weight than that of the polymer by the polycondensation by Backnowsky et al, 4 because the enhancement of polymerizability by the 3-O-benzyl group is expected from our earlier results. [6][7][8][9] In the present paper, we report the synthesis of a linear stereoregular (1f5)-R-L-arabinofuranan by the ring-opening polymerization of 1,2,5-orthopivalate (1).…”

“…We have performed the ring-opening polymerizations of a variety of sugar ortho ester derivatives and found that substituents on the monomer played an important role in stereo- and regioregularity of the resulting polymer; − i.e., both 3- O -benzyl and 2- O -pivaloyl groups are indispensable for the stereoregular ring-opening polymerization. On the basis of this knowledge, we expect that the ring-opening polymerization of 3- O -benzyl-β- l -arabinofuranose 1,2,5-orthopivalate ( 1 ), different from that of 3- O -acetyl-β- l -arabinofuranose 1,2,5-orthobenzoate tried by Kochetkov et al, leads to a linear stereoregular 3- O -benzyl-2- O -pivaloyl-(1→5)-α- l -arabinofuranan.…”

Substituent Effects of the C6-Position on Ring-Opening Polymerization of Glucose Ortho Esters: Synthesis of Stereoregular 6-Deoxy-(1→4)-β-d-glucopyranan

“…We have chemically synthesized cellulose by the ring-opening polymerization of 3- O -benzyl-α- d -glucopyranose 1,2,4-orthopivalate and found that the substituents on the monomer played an important role in stereo- and regioregularities of the resulting polymer. Both the 3- O -benzyl and orthopivaloyl groups are indispensable substituents for the synthesis of stereoregular (1→4)-β-pyranan in the ring-opening polymerizations of glucose ortho ester derivatives. , Several additional 3- O -benzyl-glucose orthopivalate derivatives with the different substituents at C6-position in our laboratory: 6- O -benzyl, methyl, acetyl, pivaloyl, DL -2-methylbutyloyl, tosyl, 6-iodo, and chloro derivatives were polymerized. Only 6- O -benzyl, methyl, and pivaloyl derivatives gave stereoregular (1→4)-β-pyranan.…”

“…Both the 3-Obenzyl and orthopivaloyl groups are indispensable substituents for the synthesis of stereoregular (1f4)-βpyranan in the ring-opening polymerizations of glucose ortho ester derivatives. 2,3 Several additional 3-O-benzylglucose orthopivalate derivatives with the different substituents at C6-position in our laboratory: 4 6-Obenzyl, methyl, acetyl, pivaloyl, DL-2-methylbutyloyl, tosyl, 6-iodo, and chloro derivatives were polymerized. Only 6-O-benzyl, methyl, and pivaloyl derivatives gave stereoregular (1f4)-β-pyranan.…”