Copolymerization of 1,6-anhydroglucose and 1,6-anhydromaltose derivatives

The copolymerization of 1,6-anhydro-2,3,4-tri-O-(p-methyl-benzyl)-β-D -glucopyrnose [TXGL, M₁] with 1,6-anhydro-2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-α-D -glucopyranosyl)-β-D -glucopyranose [HBMA, M₂] has been studied as a method of producing dextrans of controlled composition with a linear backbone and randomly distributed single glucose units as side chains. Copolymers of intrinsic viscosities ranging from 0.51 to 0.05 dl/g are produced. The copolymerization appears to follow classical copolymerization theory but is affected adversely by the low reactivity of the maltose derivative. Reactivity ratios have been calculated for runs catalyzed by 10 mole-% and 20 mole-% phosphorus pentafluoride (PF₅): r₁ = 1.91 ± 0.35, r₂ = 0.28 ± 0.25 and r₁ = 2.21 ± 0.15, r₂ = 0.21 ± 0.10, respectively.     

An analytical evaluation of anhydrosugar polymerizations

1,6-Anhydro-2,3,4-tri-O-(p-methylbenzyl)-β-D-glucopyranose (TXGL, M₁) has been copolymerized with 1,6-anhydro-2,3,4-tri-O-benzyl-β-D-glucopyranose (TBGL, M₂). Reactivity ratios, calculated by the Mayo and Lewis procedure, are r₁ = r₂ = 1.25 ± 0.25. Within experimental error these values represent azeotropic copolymerization. Therefore preceding interpretations of the relative reactivity of TXGL and other benzylated anhydrosugars are not incorrect because the possible effect of p-methyl substitution was ignored. Analysis of this copolymerization system and the reported copolymerizations of TXGL with 1,6-anhydro-2,3,4-tri-O-benzyl-β-D-manno-(TBMN) and galactopyranoses (TBGA) by the linear method recently proposed by Kelen and Tudos has confirmed that true copolymerization takes place in all the systems mentioned above and that the classical copolymerization theory adequately describes the copolymerization mechanism. Physical properties of the copolymers of TXGL and TBGL indicate the usual high stereoregularity of structure.     

Cationic ring-opening polymerization of new 1,6-anhydro-β-lactose derivatives

Synthesis and cationic ring-opening polymerization of new 1,6-anhydro-β-lactose derivatives such as hexa-O-methylated (LSHME), tert-butyldimethylsilylated (LSHSE), and benzylated 1,6-anhydro-β-lactoses (LSHBE) were first investigated. The disaccharide monomers were prepared by methylation, tert-butyldimethylsilylation, and benzylation of 1,6-anhydro-β-lactose, respectively. It was found that LSHME was readily polymerized with such Lewis acid catalysts as PF₅ and SbCl₅ to give stereoregular 2,3-di-O-methyl-4-O-(2′,3′,4′,6′-tetra-O-methyl-β-D -galactopyranosyl)-(1→6)-β-D -glucopyranans which are comb-shaped polysaccharide derivatives. However, LSHSE and LSHBE had almost no polymerizability. It was revealed that the ring-opening polymerizability of the anhydrodisaccharide monomers was influenced by the steric hindrance of the hydroxyl-protective groups. Ring-opening copolymerization of LSHME with 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose (LGTBE) in various ratios of monomer feeds was also examined to afford the corresponding copolymers. Structural analyses of the monomers and polymers were carried out by means of high resolution nuclear magnetic resonance spectroscopy.     

Copolymerization of 1,6-anhydro-ß-D-galactopyranose and 1,6-anhydro-ß-D-mannopyranose derivatives

1,6-Anhydro-2,3,4-tri-O-(p-methylbenzyl)-ß-D -galactopyranose (TXGal,M₁) has been copolymerized with 1,6-anhydro-2,3,4-tri-O-benzyl-ß-D -mannopyranose (TBMan,M₂), the products characterized by NMR, specific rotation, and viscosity, and the reactivity ratios calculated. The reactivity ratios r₁ = 0.37 ± 0.15 and r₂ = 38 ± 4 indicate that the anhydromannose derivative is about 100 times as reactive as that of anhydrogalactose. A comparison of glucose, mannose, and galactose copolymerizations suggests that the reactivity differences of the three propagating cations are comparatively small and the reactivity differences of the monomers large. This result is consistent with a mechanism proposed earlier. Methyl substitution on the aromatic rings of the p-xylyl groups inhibits the initiation process significantly relative to benzyl, but propagation only slightly.     

Acid-catalyzed polymerization of 1,6-anhydro-β-D-glucopyranose

A number of 1,6-anhydrides were polymerized in the melt at 115°C by use of monochloroacetic acid as catalyst. In the early stages of polymerization (up to 40–50% monomer consumed), each monomer was found to disappear by a first-order rate process. The 1,6-anhydrides investigated and their relative rates of polymerization were: 1,6-anhydro-2-O-methyl-β-D -glucopyranose, 1.0; 1,6-anhydro-3,4-di-O-methyl-β-D -glucopyranose, 1.4; 1,6-anhydro-2-O-methyl-β-D -galactopyranose, 2.3; 1,6-anhydro-3-O-methyl-β-D -glucopyranose, 2.6; 1,6-anhydro-4-O-methyl-β-D -glucopyranose, 6.3; 1,6-anhydro-4-O-(β-D -glucopyranosyl) β-D -glucopyranose, 9.0; 1,6-anhydro-β-D -galactopyranose, 17; 1,6-anhydro-β-D -glucopyranose, 37; 1,6-anhydro-β-D -mannopyranose, 91; and 1,6-anhydro-2-deoxy-β-D -arabino-hexopyranose, 240. The effect of substitution on the rate of polymerization suggests this reaction is mechanistically related to the acid hydrolysis of pyranosides. The results suggest that polymerization proceeds in two stages: (1) an initial build-up of dimer followed by (2) a slower growth to higher molecular weight material.     

Synthesis and properties of stereoregular 2,3,4-tri-o-acetyl-[1 → 6]-α-D-gluco-, -manno-, and -galactopyranans

Polymerization 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -mannopyranose at ?60°C with phosphorus pentafluoride (0.9 mole-%) gives stereoregular 2,3,4-tri-O-benzyl-[1 → 6]-α-D -mannopyranan with substantially higher viscosity ([η] = 2.8 dl/g) than the corresponding gluco- and glactopyranan derivatives prepared similarly. Debenzylation with sodium in liquid ammonia produces stereoregular [1 → 6]-α-D -mannopyranan of viscosity up to [η] = 0.54 dl/g. Stereoregular 2,3,4-tri-O-acetyl-[1 → 6]-α-D -glycopyranans are most simply prepared by acetylation of the corresponding crude [1 → 6]-α-D -glycopyranans obtained directly from the debenzylation reaction. The galactan is extremely difficult to acetylate by conventional methods if isolated in a pure form. Physical and spectral properties of these highly stereoregular synthetic 2,3,4-tri-O-acetyl-[1 → 6]-α-D -glycopyranans are presented. Optical rotary dispersion curves of 2,3,4, tri-O-acetyl-[1 → 6]-α-D -glycopyranans show small Cotton effects in the 200–230 nm region, superimposed on strong background rotation. Circular dichroism spectra show a single n →^* acetate absorption band for each polymer. The sign of the band appears to be determined largely by the C-2 configuration. Stereoregular 2,3,4-tri-O-acetyl-[1 → 6]-α-D -glycopyranans in 2,2,2-trifluoroethanol solution are likely to possess a random rather than helical conformation.     

Talopyranose Derivatives Suitable for the Planned Synthesis of Teichoic Acids Containing Di-Glycosylated Ribitol Units

ABSTRACT

Easily accessible 1,6-anhydro-2,3-O-(S)-benzylidene-β-D-mannopyranose was converted in four steps to 1,6-anhydro-3,4-di-O-benzyl-β-D-talopyranose. Glycosylation of the latter with ethyl 2,3,4-tri-O-acetyl-1-thio-α-L-rhamnopyranoside gave, after further processing, 1-O-allyl-3,4-di-O-benzyl-2-O-(2,3,4-tri-O-benzyl-α-L-rhamnopyranosyl)-L-ribitol.     

Graft copolymerization of anhydro sugar derivatives from macromolecular halides

Cationic graft copolymerizations of bicyclic acetals, 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose (LGTBE) and 1,6-anhydro-2,3,4-tri-O-methyl-β-D -glucopyranose (LGTME), were investigated with macromolecular carbenium ions formed from polymers that contain reactive halogens. Macromolecular complex catalysts formed from chlorosulfonated polyethylene or poly(isoprene-co-chloromethylstyrene) by the action of phosphorus pentafluoride yielded graft copolymers with low proportions (0.6–16%) of poly(LGTBE) or poly(LGTBE-co-epichlorohydrin) branchings. It was found that macromolecular complex catalysts formed from poly(styrene-co-fluoromethylstyrene) or poly(methyl methacrylate-co-fluoromethylstyrene) by the action of boron trifluoride etherate give graft copolymers with high proportions (up to 80%) of poly(LGTBE) or poly(LGTME) branchings. In addition, the model reactions for the graft copolymerization of LGTBE were examined with organic halide-PF₅, organic halide-AgPF₆, and organic fluoride-BF₃·OEt₂ catalytic systems, of which the last two indicate that the polymerization is effected by a carbenium ion mechanism.     

Synthesis and ring-opening polymerization of new 1,4-anhydro-glucopyranose derivatives

Three new 1,4-anhydro-glucopyranose derivatives having different hydroxyl protective groups such as 1,4-anhydro-2,3,6-tri-O-methyl-α-D -glucopyranose (AMGLU), 1,4-anhydro-6-O-benzyl-2,3-di-O-methyl-α-D -glucopyranose (A6BMG), and 1,4-anhydro-2,3-di-O-methyl-6-O-trityl-α-D -glucopyranose (A6TMG) were synthesized from methyl α-D -glucopyranoside in good yields. Their polymerizability was compared with that of 1,4-anhydro-2,3,6-tri-O-benzyl-α-D -glucopyranose (ABGLU) reported previously. The trimethylated monomer, AMGLU, was polymerized by a PF₅ catalyst to give 1,5-α-furanosidic polymer having number-average molecular weights (M̄_n) in the range of 2.8 × 10³ to 6.8 × 10³. The ¹³C-NMR spectrum was compared with that of methylated amylose and cellulose. Other anhydro monomers, A6BMG and A6TMG, gave the corresponding 1,5-α furanosidic polymers having M̄_n = 17.1 × 10³ and 1.8 × 10³, respectively. Thus, the substituents at the C2 and C6 positions were found to play an important role for the ring-opening polymerizability of the 1,4-anhydro-glucose monomers. In addition, debenzylation of the tribenzylated polymer gave free (1 → 5)-α-D -glucofuranan. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 841–850, 1998     

Synthesis of Hyperbranched Polysaccharide by Thermally Induced Cationic Polymerization of 1,6-Anhydrohexopyranose

The thermally induced cationic polymerizations of 1,6-anhydro-β-D -glucopyranose ( 1a ), 1,6-anhydro-β-D -mannopyranose ( 1b ) and 1,6-anhydro-β-D -galactopyranose ( 1c ) as a latent cyclic AB₄-type monomer were carried out using (S-2-butenyl)tetramethylenesulfonium hexafluoroantimonate ( 2 ) as an initiator. The solution polymerization in propylene carbonate proceeded without gelation to produce the water-soluble hyperbranched polysaccharides ( 3a-c ) with controlled molecular weights and narrow polydispersities. The degree of branching (DB), estimated by the methylation analysis of 3a-c , was in the range of 0.38 – 0.49. The thermally induced cationic polymerization of 1a-c using 2 is a facile method leading to a hyperbranched polysaccharide with a high DB value.     

An Efficient Method for the Synthesis of A 1,6-Anhydro-α-D-Galactofuranose Derivative and its Application in the Synthesis of Oligosaccharides

ABSTRACT

Synthesis of 1,6-anhydro-2,3,5-tri-O-benzoyl-β-D-galactofuranose (3) has been achieved in good yield by stannic chloride catalysed ring closure of methyl 2,3,4-tri-O-benzoyl-6-O-benzyl-β-D-galactofuranoside (1). The anhydro compound 3 was converted to the furanoside donors 6 and 7 with an easily removable O-6 acetyl group. The donors 6 and 7 were utilised for the synthesis of a di- and a trisaccharide containing β-D-galactofuranosides.     

Synthesis of a (1→6)-β-Linked N-Acetyl-d-glucosamine Oligosaccharide1

Abstract

1,6-Anhydro-2-deoxy-3,4-di-O-benzyl-2-phthalimido-β-d- glucopyranose (5) was synthesized from 1,6-anhydro-β-d-mannopyranose (1) in five steps. Compound 5 was polymerized under cationic conditions and selectively yielded glucosamine oligomers (degree of polymerization 5-7). Copolymerization of 5 with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose indicated the low reactivity of 5 with the active cation derived from 5. Deprotection of 2-deoxy-3,4-di-O-benzyl-2-phthalimido-(1→6)-β-d-glucopyranan (7) and N-acetylation gave 2-acetamido-2-deoxy-(1→6)-β-d-glucopyranan (9).     

Precision synthesis of (1→6)-α-D-glucopyranan by cationic ring-opening polymerization of 1,6-anhydro-2,3,4-tri-O-allyl-β-D-glucopyranose

The ring-opening polymerization of 1,6-anhydro-2,3,4-tri-O-allyl-β-D-glucopyranose ( 2 ) has been carried out using various cationic initiators. For the condition of [ 2 ]/[BF₃·OEt₂] = 20 at −15°C for 90 h, the polymer yield, M_w and M_w/M_n of the polymer obtained were 79%, 215,600 and 3.45, respectively. In order to study the living characteristic of the polymerization of 2 , the cationic ring-opening bulk polymerization initiated by trimethylsilyl trifluoromethanesulfonate (TMSOTf) was carried out under the condition of [ 2 ]/[TMSOTf] = 1000 at −15 °C. The M_w value increased in proportion to conversion until c.a. 30% and below. The M_w/M_ns of resulting polymers were very narrow, e.g., the M_w/M_n value was 1.2 and below, which was smaller than that for the solution polymerization using BF₃·OEt₂. These results indicated that the ring-opening bulk polymerization of 2 using TMSOTf was living-like.     

Aminobutadienes. X. Polymerization and copolymerization of 2-phthalimidomethyl-1,3-butadiene

The polymerization and copolymerization of 2-phthalimidomethyl-1,3-butadiene were investigated. This monomer was easily polymerized by benzoyl peroxide catalyst in bulk or in solvent, and by γ-radiation in the solid state to give polymers having a softening point of 135–145°C. Although these resulting polymers did not give x-ray diffraction patterns, they showed crystalline patterns by electron diffraction. On the other hand, cationic polymerization with the use of boron trifluoride diethyl etherate in chloroform was attempted, but no formation of the polymer was observed. Also, this monomer was easily copolymerized with styrene in N,N-dimethylformamide. The monomer reactivity ratios and Alfrey-Price Q and e values calculated from the copolymerization data of this monomer (M₁) with styrene (M₂) were r₁ = 2.0 ± 0.13, r₂ = 0.15 ± 0.02, and Q₁ = 2.78, e₁ = 0.30.     

Synthesis of stereoregular heteropolysaccharides having amino-groups by ring-opening copolymerization of 1,6-anhydro-azido-sugar derivatives

The cationic, ring-opening copolymerization of 1,6-anhydro-2-azido-3,4-di-0-benzyl-2-deoxy-(2-ABG), -3-azido-2,4-di-0-benzyl-3-deoxy- (3-ABG), -4-azido-2,3-di-0-benzyl-4-deoxy-β-D -glucopyranose (4-ABG) with 1,6-anhydro-2,3,4-tri-0-benzyl-β-D -glucopyranose (LGTBE) was investigated with phosphorus pentafluoride as catalyst at low temperatures, giving highly stereoregular, (1→6)-α-linked copolymers with number-average molecular weights of 3.90 × 10⁴?9.27 × 10⁴. Structure and composition of the copolymers were determined by ¹H- and ¹³C-NMR spectroscopies and elemental analysis, which indicated that copolymerization occurred in a stereoregular manner to give azido groups containing (1→6)-α-linked glucopyranan derivatives. The differences in polymerizability among the three azido monomers are discussed. Regioselective reduction of three kinds of heteropolysacharide derivatives which had different quantities of azido groups at C-2, -3, or -4 position with lithium aluminum hydride and subsequent debenzylation of the copolymers with sodium in liquid ammonia produced amino-group-containing heteropolysaccharides.     

C-Glycoside Analogues of N4-(2-Acetamido-2-deoxy-β-D-glucopyranosyl)-L-asparagine: Synthesis and conformational analysis of a cyclic C-glycopeptide

The synthesis of C-glycosidic analogues 15–22 of N⁴-(2-acetamido-2-deoxy-β-D -glucopyranosyl)-L -asparagine (Asn(N⁴GlcNAc)) possessing a reversed amide bond as an isosteric replacement of the N-glycosidic linkage is presented. The peptide cyclo(-D -Pro-Phe-Ala-CGaa-Phe-Phe-) (CGaa = C-glycosylated amino acid; 24 ) was prepared to demonstrate that 3-[(3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-β-D -glycero-D -guloheptonoyl)amino]-2-[(9H-fluoren-9-yloxycarbonyl)amino]propanoic acid ( 22 ) can be used in solid-phase peptide synthesis. The conformation of 24 was determined by NMR and molecular-dynamics (MD) techniques. Evidence is provided that the CGaa side chain interacts with the peptide backbone. The different C-glycosylated amino acids 15–21 were prepared by coupling 3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-β-D -glycero-D -gulo-heptonic acid ( 4 ) with diamino-acid derivatives 8–14 in 83–96% yield. The synthesis of 4 was performed from 2-(acetamido-3,4,6-tri-O-benzyl-2-deoxy-β-D -glucopyranosyl) tributylstannane ( 2 ) by treatment with BuLi and CO₂ in 83% yield. Similarly, propyl isocyanat yielded the glycoheptonamide 7 in 52% from 2 . Compound 2 was obtained from 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-D -glucopyranose ( 1 ) by chlorination and addition of tributyltinlithium in 74% yield. A procedure for a multigram-scale synthesis of 1 is given.     

Synthesis and polymerization of 5‐(methacrylamido)tetrazole,a water‐soluble acidic monomer

The reaction of methacryloyl chloride with 5‐aminotetrazole gave the polymerizable methacrylamide derivative 5‐(methacrylamido)tetrazole ( 4 ) in one step. The monomer had an acidic tetrazole group with a pK_a value of 4.50 ± 0.01 in water methanol (2:1). Radical polymerization proceeded smoothly in dimethyl formamide or, after the conversion of monomer 4 into sodium salt 4‐Na , even in water. A superabsorbent polymer gel was obtained by the copolymerization of 4‐Na and 0.08 mol % N,N′‐methylenebisacrylamide. Its water absorbency was about 200 g of water/g of polymer, although the extractable sol content of the gel turned out to be high. The consumption of 4‐Na and acrylamide (as a model compound for the crosslinker) during a radical polymerization at 57 °C in D₂O was followed by ¹H NMR spectroscopy. Fitting the changes in the monomer concentration to the integrated form of the copolymerization equation gave the reactivity ratios r _4‐Na = 1.10 ± 0.05 and r_acrylamide = 0.45 ± 0.02, which did not differ much from those of an ideal copolymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4333–4343, 2002     

Cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D‐glucopyranose as a convenient synthesis of dextran

For the convenient synthesis of (1→6)‐α‐D ‐glucopyranan, i. e., dextran ( 4 ), ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D ‐glucopyranose ( 1 ) has been carried out using BF₃·OEt₂. With a ratio of [BF₃·OEt₂]/[ 1 ] = 0.5 at 0 °C for 140 h, the yield and M_n of the obtained polymer are 84.0% and 21 700, respectively. The polymer consists of (1→6)‐α‐linked 2,3,4‐tri‐O‐allyl‐D ‐glucopyranose ( 2 ) which is similar to the results for the cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐methyl‐β‐D ‐glucopyranose and 1,6‐anhydro‐2,3,4‐tri‐O‐ethyl‐β‐D ‐glucopyranose. Polymer 2 was isomerized using tris(triphenylphosphine)‐chlororhodium as the catalyst in toluene/ethanol/water to yield polymeric 2,3,4‐tri‐O‐propenyl‐(1→6)‐α‐D ‐glucopyranan ( 3 ). Deprotection of the propenyl ether linkage of 3 was then performed using hydrochloric acid in acetone to give 4 .     

Emulsion copolymerization of styrene and methyl methacrylate

Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10^?5 for styrene polymerization and 0.4 × 10^?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10^?5. Reactivity ratios measured in emulsion were r₁ (styrene) = 0.44, r₂ = 0.46. Those in bulk polymerizations were r₁ = 0.45, r₂ = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known.     

Synthesis of polymers having photocrosslinkable moieties for second-order nonlinear optics

Second-order non-linear optical polymers having photocrosslinkable moieties were synthesized by cationic polymerization of monomer (I) and monomer (II). The polymerization proceeded rapidly to give linear polymers in high yields. Monomer reactivity ratios were calculated to be r₁ = 0.90 and r₂ = 0.96 (r₁r₂ = 0.86), indicating that these monomers copolymerized through the almost ideal copolymerization mechanism. The photocrosslinking reaction of an equimolar copolymer film underwent the conversion of up to ca. 70% upon irradiation with a 500 W high-presure mercury lamp for 5 min. The electric field induced polar orientation of the chromophores (pendant 4-nitrophenyloxy groups) in a photocrosslinked polymer was stable for more than 10 days. This polymer exhibits a nonlinear coefficient d₃₃ of 5.6 × 10^-10 esu measured at a pumping wavelength of 1064 nm.