Dehydration of raffinose pentahydrate: structures of raffinose 5‐, 4.433‐, 4.289‐ and 4.127‐hydrate at 93 K

Raffinose [or O‐α‐D‐galactopyranosyl‐(1→6)‐α‐D‐glucopyranosyl‐(1→2)‐β‐D‐fructofuranoside] pentahydrate, C₁₈H₃₂O₁₆·5H₂O, (I), and three lower hydrates, namely the 4.433‐, (II), 4.289‐, (III), and 4.127‐hydrated, (IV), forms, obtained in the course of the dehydration of (I), have been studied. The unit cells in the space group P2₁2₁2₁ are of similar dimensions for all the crystals. The conformation of the raffinose molecules remains almost the same across the four crystal structures. The raffinose molecules are linked into a three‐dimensional hydrogen‐bonded network involving all the –OH groups, the ring and glycosidic O atoms, and the water molecules. Six water sites were identified in the structures of (II), (III) and (IV), of which W1, W4 and W6 (W = water) are partially occupied with their populations coupled. W1, W4 and one of the –OH groups of the galactose ring form an infinite hydrogen‐bonding chain around a 2₁ axis parallel to the a axis (denoted chain A), and W6 and the same –OH group form a similar chain (chain A′) disordered with chain A. The occupancy ratio of chain A to chain A′ for N‐hydrates (N is a hydration number between 4 and 5) is (N− 4):(5 −N). The transformation of chain A to chain A′ as part of the dehydration process has little effect on the rest of the structure. Thus, the dehydration proceeds without significant impact on the crystal structure.     

Synthesis of an Aminooxy Derivative of the Trisaccharide Globotriose Gb3

The synthesis of α-aminooxy trisaccharide moiety [α-d-Gal-(1,4)-β-d-Gal-(1,4)-β-d-Glc-α-aminooxy], related to the cell surface globotriaosylceramide (Gb3) receptor of the B subunit of the AB₅ Shiga toxin of Shigella dysenteriae, has been carried out for the first time in 11 steps with a 15% overall isolated yield. A highlight of this work entails utilizing chemically compatible synthetic transformations, including those related to glycosylation, incorporative of the succinimidyl moiety as a precursor to the aminooxy Gb3 derivative. The fully deprotected trisaccharide aminooxy compound was reacted with a carbonyl compound, leading to oxime formation in quantitative yield, which underscores the importance for future glyco-conjugations.     

高效液相色谱法测定糖化酶中葡萄糖苷转移酶的活性

建立了糖化酶中葡萄糖苷转移酶活性测定的高效液相色谱方法。以麦芽糖为底物,阿卡波糖为抑制剂,在37 ℃、pH=4.8醋酸缓冲液介质中葡萄糖苷转移酶作用下将麦芽糖转化为三糖。采用SUGAR SH1011色谱柱（300 mm×8.0 mm,6 μm）分离,以0.01 mol/L硫酸水溶液为流动相,流速0.6 mL/min,用示差折光检测器检测测定三糖的转化量,间接测定葡萄糖苷转移酶的活性。对色谱条件、底物浓度、抑制剂用量及培养时间等条件进行了系统考察。在优化的条件下,三糖在0.1~10 g/L范围内线性关系良好（r=0.9998）,葡萄糖苷转移酶活性检出限和定量限分别为0.013 U和0.043 U,6次平行测定的相对标准偏差（RSD）为0.63%。在优化条件下测定了不同批次糖化酶中葡萄糖苷转移酶的活性,结果良好。该方法操作简便,稳定性高,可用于葡萄糖生产原料糖化酶中葡萄糖苷转移酶活性的测定。     

Synthesis of the Cellulose Model Compound Methyl 4″-O-Methyl-β-D-Cellotrioside

A high-yield synthetic route towards methyl 4″-O-methyl-β-D -cellotrioside ( 17 ) via cellobioside acceptor 8 and glucosyl fluoride donor 15 was established. The former was synthesized from cellobiose peracetate in 7 steps and 21% overall yield, while the latter was obtained from methyl β-D -glucopyranoside in a 6-step-synthesis with 19% yield. Glycosidation afforded 13% of α-compound besides the desired β-isomer (31%). The target compound, being the higher homologue of the recently prepared 4′-O-methyl-β-D -cellobioside ( 1 ), is required to study by solid-state techniques the hydrogen bond network in cellodextrins and cellulose, and its changes upon swelling and dissolution.     

A convenient synthesis of the core trisaccharide of the N-glycans

A convenient synthesis of the core trisaccharide of the N-glycans was described. Orthogonal one-pot glycosylation of three monosaccharide building blocks was performed to furnish β-glucosyl chitobiose, which was then transformed to β-mannosyl chitobiose by intramolecular epimerization of the C-2 position of the β-glucoside. The key glucosyl donor 7c with differentiated 2,3-OH was prepared following the 4,6-O-benzylidene-protected 1,2-orthoester strategy.     

Specific lectin interactions and temperature‐induced reversible gels in novel water‐soluble glycopolymers bearing maltotrionolactone pendant groups

Glycopolymers based on the incorporation of a diaminobutylmaltotrionolactone onto activated ethylene‐vinyl alcohol, EVOH, copolymers with distinct composition in the former counit have been prepared. Previous transformation of initial hydroxyl EVOH groups to other more reactive functional groups has been required. The activation has been performed in this current investigation by functionalization with either 4‐nitrophenyl carbonate or o‐phthalic acid groups. The structure of the resulting novel water‐soluble glycopolymers has been confirmed by FTIR, ¹H and ¹³C‐NMR spectroscopies. In addition, the glass transition temperatures and thermal stability as well as the viscoelastic behavior in bulk and in water solution have been examined as a function of chemical linkage nature. The rheological evaluation confirms the reversible gel formation in all the cases. Finally, their affinity to Concanavalin A lectin has been also analyzed proving the feasible use of these glycopolymers as molecular recognition materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 719–729, 2010