- Anomeric alkylations and acylations of unprotected mono- and disaccharides mediated by pyridoneimine in aqueous solutions
-
A site-specific deprotonation followed by alkylations and acylations of sugar hemiacetals to the corresponding alkyl glycosides and acylated sugars in aqueous solutions is disclosed herein. Pyridoneimine as a new base is developed to mediate the deprotonation of readily available sugar hemiacetals and further reactions with alkylation and acylation agents.
- Dey, Kalyan,Jayaraman, Narayanaswamy
-
supporting information
p. 2224 - 2227
(2022/02/17)
-
- A 1H NMR study of the specificity of α-l- arabinofuranosidases on natural and unnatural substrates
-
Background The detailed characterization of arabinoxylan-active enzymes, such as double-substituted xylan arabinofuranosidase activity, is still a challenging topic. Ad hoc chromogenic substrates are useful tools and can reveal subtle differences in enzymatic behavior. In this study, enzyme selectivity on natural substrates has been compared with enzyme selectivity towards aryl-glycosides. This has proven to be a suitable approach to understand how artificial substrates can be used to characterize arabinoxylan-active α-l-arabinofuranosidases (Abfs). Methods Real-time NMR using a range of artificial chromogenic, synthetic pseudo-natural and natural substrates was employed to determine the hydrolytic abilities and specificity of different Abfs. Results The way in which synthetic di-arabinofuranosylated substrates are hydrolyzed by Abfs mirrors the behavior of enzymes on natural arabinoxylo-oligosaccharide (AXOS). Family GH43 Abfs that are strictly specific for mono-substituted d-xylosyl moieties (AXH-m) do not hydrolyze synthetic di-arabinofuranosylated substrates, while those specific for di-substituted moieties (AXH-d) remove a single l-arabinofuranosyl (l-Araf) group. GH51 Abfs, which are supposedly AXH-m enzymes, can release l-Araf from disubstituted d-xylosyl moieties, when these are non-reducing terminal groups. Conclusions and general significance The present study reveals that although the activity of Abfs on artificial substrates can be quite different from that displayed on natural substrates, enzyme specificity is well conserved. This implies that carefully chosen artificial substrates bearing di-arabinofuranosyl d-xylosyl moieties are convenient tools to probe selectivity in new Abfs. Moreover, this study has further clarified the relative promiscuity of GH51 Abfs, which can apparently hydrolyze terminal disubstitutions in AXOS, albeit less efficiently than mono-substituted motifs.
- Borsenberger, Vinciane,Dornez, Emmie,Desrousseaux, Marie-Laure,Massou, Stéphane,Tenkanen, Maija,Courtin, Christophe M.,Dumon, Claire,O'Donohue, Michael J.,Fauré, Régis
-
p. 3106 - 3114
(2014/09/17)
-
- Enzymatic Synthesis of Aroma Compound Xylosides Using Transfer Reaction by Trichoderma longibrachiatum Xylanase
-
Enzymatic synthesis of aroma compound xylosides was performed by Trichoderma longibrachiatum xylanase. Information concerning the nature of xylosides present in the reaction medium was obtained by GC-EI-MS, by GC-NCI-MS of TFA derivatives, and by positive
- Kadi, Nadia,Belloy, Laurence,Chalier, Pascale,Crouzet, Jean Claude
-
p. 5553 - 5557
(2007/10/03)
-
- Stereoselective Syntheses of α-Glucuronides Using Dehydrative Glycosylation
-
Methyl and benzyl 2,3,4-tri-O-benzyl-D-glucopyranuronates, prepared from D-glucurono-6,3-lactone, afforded selectively the corresponding α-glucopyranosiduronates by the aid of the condensing reagent system composed of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine. Using this method, O-α-D-glucopyranuronosyl-(1→3)-O-α-L-arabinofuranosyl- (1→3)-D-xylopyranose, one of the minimal component units in the structure of plantago-mucilage A from the seeds of Plantago asiatica Linne constituting a Chinese medicine : chegianzi [HU~P].
- Koto, Shinkiti,Miura, Teruhisa,Hirooka, Motoko,Tomaru, Aya,Iida, Mika,Kanemitsu, Masanori,Takenaka, Kazuhiro,Masuzawa, Shinichi,Miyaji, Saeko,Kuroyanagi, Naoko,Yagishita, Miki,Zen, Shonosuke,Yago, Kazuo,Tomonaga, Fumiya
-
p. 3247 - 3259
(2007/10/03)
-
- 4-O-β-D-Galactopyranosyl-D-xylose: A new synthesis and application to the evaluation of intestinal lactase
-
4-O-β-D-Galactopyranosyl-D-xylose (2) was prepared from benzyl 2,3-O-isopropylidene-β-D-xylopyranoside by glycosylation with 2,3,4,6-tetra-O-benzoyl-α-D-galactopyranosyl bromide and subsequent deprotection. Compound 2 was hydrolyzed in vitro by intestinal lactase; the V(max) was 25% of that with lactose and the K(m) was 370 mM (cf. 27 mM for lactose). Oral administration of 2 to suckling rats led to urinary excretion of D-xylose which could be estimated colorimetrically. 4-O-β-D-Galactopyranosyl-D-xylose (2) was prepared from benzyl 2,3-O-isopropylidene-β-D-xylopyranoside by glycosylation with 2,3,4,6-tetra-O-benzoyl-α-D-galactopyranosyl bromide and subsequent deprotection. Compound 2 was hydrolyzed in vitro by intestinal lactase; the Vmax was 25% of that with lactose and the Ktu was 370mM (cf. 27mM for lactose). Oral administration of 2 to suckling rats led to urinary excretion of D-xylose which could be estimated colorimetrically.
- Rivera-Sagredo,Fernandez-Mayoralas,Jimenez-Barbero,Martin-Lomas,Villanueva,Aragon
-
p. 129 - 135
(2007/10/02)
-
- Pseudomonic Acid C from L-Lyxose
-
Full details of the total synthesis of pseudomonic acid C from L-lyxose are described.Key features of the approach involve feee-radical allylation for stereoselective C-C bond formation at C4 of lyxose, Frater alkylation to generate correct stereochemistry at C12 and C13, and stereoselective intramolecular Michael addition to establish the correct stereochemistry of the "anomeric" appendage.
- Keck, Garry E.,Kachensky, David F.,Enholm, Eric J.
-
p. 4317 - 4325
(2007/10/02)
-
- Total Synthesis of Pseudomonic Acid C
-
A convergent total synthesis of pseudomonic acid C from L-lyxose is described in which a highly stereoselective free-radical C-C bond construction plays a key role.
- Keck, Gary E.,Kachensky, David F.,Enholm, Eric J.
-
p. 1462 - 1464
(2007/10/02)
-