factor by uncovering toxin binding sites.6 Inhibition of
neuraminidase has afforded potential strategies for the
development of antiviral and antibacterial agents.7,8 Two
neuraminidase inhibitors, Zanamirvir (Relenza, Glaxo Smith-
Kline) and Oseltamivir (Tamiflu, Hoffman-La Roche), are
currently used clinically as prophylactic agents against
influenza.9
Scheme 1a
Several groups have developed inhibitors of the influenza
virus that are polyvalent in Neu5Ac.10 The synthetic random
copolymers incorporating Neu5Ac C-glycoside moieties have
been shown to be effective in inhibiting influenza virus-
induced agglutination of erythrocytes in vitro.11 Our labora-
tory has extensive experience in the chemoenzymatic syn-
thesis of synthetic polymers containing sugar pendents.12 We
have also been particularly interested in the synthesis and
biological evaluation of neuraminic acid containing mol-
ecules.13 The current study is focused on developing the
highly efficient synthesis of catabolically stable neuraminic
acid based C-glycoside polymers for investigation as poten-
tial biomaterials for application as antimicrobial barriers.
Two such polymers were generated in this study, both
based on the initial formation of C-glycosides of neuraminic
acid. The first route involves the enzymatic polymerization
of a phenolic C-glycoside with soybean peroxidase. The
second route involves the vinyl polymerization of a terminal
allyl group on the aglycone.
C-Glycosylation donor, peracetylated neuraminic acid
phenyl sulfone (1), was synthesized according to a published
procedure.14 Samarium iodide mediated C-glycosylation
chemistry was utilized to construct a C-C bond connection
between the neuraminic acid donor and an acceptor bearing
the ketone moiety.15 Compound 3 represents a Neu5Ac
C-glycoside linked to a phenolic aglycone (Scheme 1).16
Carefully designed protecting group chemistry in the donor
and the acceptor simplified monomer synthesis. Simultaneous
deprotection of the acetyl groups and hydrolysis of the methyl
ester afforded the water-soluble phenolic C-glycoside mono-
mer (4). Both 3 and 4 were racemic (R,S) mixtures at the
newly formed hydroxylmethylene glycosidic carbon. Horse-
a Reagents and conditions: (a) THF, SmI2 10 h. (b) NaOMe,
MeOH, 8 h, followed by 0.2 M KOH. (c) Soy Bean peroxidase,
H2O2, sodium phosphate buffer, pH 7.0, 18 h.
radish peroxidase (HRP) and Soybean peroxidase (SBP) are
able to catalyze C-C bond formation, at the ortho-position
of the electron donating group-containing phenolic mono-
mers, under mild conditions. Polymerization of C-glycoside
4 in aqueous sodium phosphate buffer (pH 7) with soybean
peroxidase (SBP) and H2O2 afforded a mucin-like polymer
5 having a molecular weight of 20 000.17 Molecular weight
was determined by gel permeation chromatography and
calculated based on a standard curve with use of polysac-
charide standards. The molecular weight of polymer 5 is
similar to that of MG2 mucin (MUC 7).
(6) Corfield T. Glycobiology 1992, 2, 509.
(7) Varghese, J. N. Drug DeVelop. Res. 1999, 46, 176.
(8) Johnston, S. L. Virus Res. 2002, 82, 147.
(16) To prepare methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2,6-anhydro-
3,5-dideoxy-2-C-[(2-hydroxy-butylphenyl-acetate) methyl]-D-erythro-L-
manno-nononate 3, Neu5Ac phenyl sulfone 1 (100 mg) and 5 equiv of 4-(3-
oxobutyl)phenyl acetate 2 were dried together under high vacuum for 4 h.
SmI2 (4 equiv, freshly prepared from Sm and ICH2CH2I, 0.1 M in THF)
was added under argon in one portion at room temperature with vigorous
stirring. The dark blue solution was stirred overnight. The reaction mixture
was diluted with ether and extracted with 1 N HCl, saturated Na2S2O3,
saturated NaHCO3, and brine solution. The organic layer was dried over
anhydrous Na2SO4. The filtrate was concentrated under reduced pressure
and purified on a silica gel column with EtOAc as eluent. The C-glycoside
was obtained as oil in 82% yield. 1H NMR (CDCl3) δ 1.80-2.20 (19H,
6COCH3, H-3ax, CH2CH2Ph), 2.45 (m, 1 H, H-3eq), 2.63-2.67 (ddd, 1H,
CH2Ph), 2.78-2.85 (ddd, 1H, CH2Ph), 3.76 (d, 3H, COOCH3), 3.95-4.10
(m, 3 H, H-5, H-6, H-9a), 4.34 (m, 1 H, H-9b), 4.74 (m, H-4), 5.22 (m, 1
H, NH), 5.8 (m, 1 H, H-7), 5.40 (m, 1 H, H-8). HRFABMS: calcd for
C32H43NO15Na [M + Na]+ 704.2556, found m/z 704.2530 [M + Na]+
(17) To prepare phenolic mucin analogue 5, fully deprotected monomer
4 (10 mg, 0.022 mmol) was dissolved in sodium phosphate buffer (50 mM,
pH 7, 200 µL) 80 vol % in CH3CN. Soybean peroxidase (1 mg) was added
to the solution, followed by the dropwise (10 µL/4 min) addition of H2O2
(100 µL 0.2 M). After 12 h, the reaction mixture was freeze-dried and
subjected to BioGel P-10 column to determine molecular weight. 1H NMR
of resulting polymer shows broad peaks in the phenolic and carbohydrate
regions. The intrinstic viscosity is 2.5 × 10-3 m3/kg.
(9) Johnson, S. L. Virus Res. 2002, 82, 147.
(10) (a) Reuter, J. D.; Myc, A.; Hayes, M. M.; Gan, Z.; Roy, R.; Qin,
D.; Yin, R.; Piehler, L. T.; Esfand, R.; Tomalia, D. A.; Baker, J. R., Jr.
Bioconj. Chem. 1999, 10, 271. (b) Zanini, D.; Roy, R. J. Am. Chem. Soc.
1997, 119, 2088. (c) Wu, W.; Jin, B.; Krippner, G. Y.; Watson, K. G. Bioorg.
Med. Chem. Lett. 2000, 10, 341. (d) Choi, S.-K.; Mammen, M.; Whitesides,
G. M. J. Am. Chem. Soc. 1997, 119, 4103.
(11) (a) Nagy, J. O.; Bednarrski, M. D. Tetrahedron Lett. 1991, 32, 3953.
(b) Sparks, M. A.; Williams, K. W.; Whitesides, G. M. J. Med. Chem. 1993,
36, 778.
(12) (a) Dordick, J. S.; Linhardt, R. J.; Rethwisch, D. G. Chemtech 1994,
24, 33. (b) Wang, Q.; Linhardt, R. J.; Dordick, J. S. Biotechnol. Tech. 1999,
13, 463. (c) Wang, P.; Martin, B. D.; Parida, S.; Rethwisch, D. G.; Dordick,
J. S. J. Am. Chem. Soc. 1995, 117, 12885. (d) Wang, Q.; Dordick, J. S.;
Linhardt, R. J. Chem. Mater. 2002, 14, 3232.
(13) (a) Vlahov, I. R.; Vlahov, P. I.; Linhardt, R. J. J. Am. Chem. Soc.
1997, 119, 1480. (b) Wang, Q.; Wolff, M. W.; Polat, T.; Du, Y.; Linhardt,
R. J. Bioorg. Med. Chem. Lett. 2000, 10, 941.
(14) Mazza, A.; Sinay¨, P. Carbohydr. Res. 1989, 187, 35.
(15) (a) Curran, D. P.; Fevig, T. L.; Jasperse, C. P.; Totleben, M. J. Synlett
1992, 943. (b) Molander, G. A.; Harris, C. R. Chem. ReV. 1996, 96, 307.
(c) Krief, A.; Laval, A. Chem. ReV. 1999, 99, 745. (d) Steel, P. G. J. Chem.
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