Aminoglycoside antibiotics: The formation and characterization of dihydrooxazine derivatives in the paromomycin series

1978 ◽  
Vol 56 (11) ◽  
pp. 1492-1499 ◽  
Author(s):  
Stephen Hanessian ◽  
Robert Massé ◽  
Goran Ekborg
Keyword(s):  
Chemical Modification ◽  
Zinc Chloride ◽  
Aminoglycoside Antibiotics ◽  
High Yield ◽  
Hydroxyl Groups ◽  
Model Studies ◽  
Derivatives Of ◽  
Excess Zinc ◽  
Chemical Evidence

Treatment of penta-N-benzyloxycarbonylparomomycin with benzaldehyde and excess zinc chloride gives a dibenzylidene derivative in high yield. This consists of the 4′,6′-O-benzylidene 4′′′,6′′′-N,O-benzylidene (dihydrooxazine) derivative of penta-N-benzyloxycarbonylparomomycin. Chemical evidence is presented to support this structure and model studies are reported for the formation of dihydrooxazine and oxazolidine derivatives of benzyloxycarbonylamino sugars containing suitably situated hydroxyl groups. The easily obtained dihydrooxazine derivative of paromomycin constitutes an interesting, preferentially blocked derivative, that is useful for the chemical modification of the parent antibiotic.

scholarly journals Lignin-based polyurethane and epoxy adhesives: a short review

2021 ◽  
Vol 2 (107) ◽  
pp. 56-63
Author(s):  
D.J. dos Santos ◽  
L.B. Tavares ◽  
J.R. Gouveia ◽  
G.F. Batalha
Keyword(s):  
Molecular Structure ◽  
Chemical Modification ◽  
Raw Materials ◽  
Short Review ◽  
Thermomechanical Properties ◽  
Hydroxyl Groups ◽  
Potential Candidate ◽  
Phenolic Resins ◽  
Polyurethane Adhesives

Purpose: of this paper was to review and summarize significant papers related to the development and characterization of lignin-containing adhesives: polyurethane and epoxy types. In the last decades, several efforts have been dedicated on the development of renewable raw materials for polymer synthesis, mainly due to petroleum depletion and sustainability. In this context, lignin emerged as a potential candidate to substitute fossilbased raw materials in adhesive synthesis and formulations. Design/methodology/approach: Recent and other relevant papers were reviewed, aiming to identify the main advantages and limitations involved in lignin incorporation into epoxy and polyurethane adhesives formulations. First, effects of unmodified lignin addition were presented. Afterwards, the main lignin chemical modification methods were presented and discussed, based on thermomechanical results. Findings: Incorporation of unmodified lignin usually is limited to 30 %wt., otherwise mechanical properties are drastically affected as consequence of poor lignin solubility and excessive brittleness. Lignin chemical modification can be used to increase the reactivity of hydroxyl groups and/or add new moieties in its molecular structure, improving solubility and thermomechanical properties of cured adhesives. Practical implications: In the last years, some industrial plants started to operate and produce technical grade lignin at industrial scale, with reproducible properties and controlled molecular structure. Therefore, increasing efforts have been dedicated from researchers and chemists to develop lignin-based technologies, in which this work can directly contribute with. Originality/value: As consequence of the high content of phenol groups in its molecular structure, lignin was mostly applied on the development of phenolic resins applied as wood adhesives. For the first time in the literature, this work summarizes the advances related to synthesis and characterization of polyurethane and epoxy, applied as adhesives. Results can support the development and application of biobased, as well as contribute to the revalorization of this valuable and readily available biomass.

Characterization of Monohalogen and Monopseudohalogen Derivatives of Dimethylgermane

1974 ◽  
Vol 52 (14) ◽  
pp. 2622-2633 ◽  
Author(s):  
Geoffrey K. Barker ◽  
John E. Drake ◽  
Raymond T. Hemmings
Keyword(s):  
Force Field ◽  
Vibrational Spectra ◽  
High Yield ◽  
Normal Coordinate ◽  
Physical Methods ◽  
Valence Force Field ◽  
Fundamental Frequencies ◽  
Cleavage Reactions ◽  
Derivatives Of

The high yield syntheses of Me2GeHX (X = F, Cl, Br, I) and Me2GeHPs (Ps = CN, N3, NCO, NCS, OAc) are reported. The dimethylgermane derivatives are identified and characterized by various physical methods and by cleavage reactions where appropriate. A normal coordinate analysis based on a modified valence force field provides confirmation of the assignments for all the fundamental frequencies, except the torsional modes, in the vibrational spectra of the monohalogeno(dimethyl)germanes, Me2GeHX.

scholarly journals Chemical modification of cellulose for boron sorption from water solutions

2018 ◽  
Vol 20 (4) ◽  
pp. 123-128
Author(s):  
A. Sarsenov ◽  
V.K. Bishimbaev ◽  
B.A. Kapsalamov ◽  
K.K. Lepesov ◽  
K.M. Gapparova ◽  
...  
Keyword(s):  
Chemical Modification ◽  
Juglans Regia ◽  
Walnut Shell ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Coupling Technique ◽  
Coupling Process ◽  
Polyhydric Alcohols ◽  
Natural Cellulose ◽  
Derivatives Of

Abstract It is shown that natural cellulose obtained from the walnut shell (Juglans regia) can be used for chemical modification of the selective boron sorbent. The modification was carried out by the coupling technique of chlorine derivatives of the polyhydric alcohols or polyols (mannitol, xylitol, sorbitol or glycerol). In this case new hybrid substances (sorbents) were obtained and they are represented by the formula: R-O-(CHOH)n-CH3, where R is a residue of the cellulose backbone, n is the number of functional (OH) groups of the polyhydric alcohols. The pulp mercerization was carried out by processing the ground walnut shell (WS) with hot solution of sodium hydroxide. Chlorination of polyhydric alcohols was carried out by gaseous hydrochloric acid sparging through the polyhydric alcohol aqueous solution. The coupling process proceeds according to the mechanism of substitution of the cellulose hydroxyl groups with chlorine atoms.

scholarly journals Identification of Novel Gymnodimines and Spirolides from the Marine Dinoflagellate Alexandrium ostenfeldii

Marine Drugs ◽  
2018 ◽  
Vol 16 (11) ◽  
pp. 446 ◽  
Author(s):  
Christian Zurhelle ◽  
Joyce Nieva ◽  
Urban Tillmann ◽  
Tilmann Harder ◽  
Bernd Krock ◽  
...  
Keyword(s):  
Chemical Diversity ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Alexandrium Ostenfeldii ◽  
Exocyclic Methylene ◽  
Polyketide Chain ◽  
Marine Dinoflagellates ◽  
Toxin Class ◽  
Derivatives Of

Cyclic imine toxins are neurotoxic, macrocyclic compounds produced by marine dinoflagellates. Mass spectrometric screenings of extracts from natural plankton assemblages revealed a high chemical diversity among this toxin class, yet only few toxins are structurally known. Here we report the structural characterization of four novel cyclic-imine toxins (two gymnodimines (GYMs) and two spirolides (SPXs)) from cultures of Alexandrium ostenfeldii. A GYM with m/z 510 (1) was identified as 16-desmethylGYM D. A GYM with m/z 526 was identified as the hydroxylated degradation product of (1) with an exocyclic methylene at C-17 and an allylic hydroxyl group at C-18. This compound was named GYM E (2). We further identified a SPX with m/z 694 as 20-hydroxy-13,19-didesmethylSPX C (10) and a SPX with m/z 696 as 20-hydroxy-13,19-didesmethylSPX D (11). This is the first report of GYMs without a methyl group at ring D and SPXs with hydroxyl groups at position C-20. These compounds can be conceived as derivatives of the same nascent polyketide chain, supporting the hypothesis that GYMs and SPXs are produced through common biosynthetic genes. Both novel GYMs 1 and 2 were detected in significant amounts in extracts from natural plankton assemblages (1: 447 pg; 2: 1250 pg; 11: 40 pg per mL filtered seawater respectively).

scholarly journals Facile fabrication of polymer network using click chemistry and their computational study

2021 ◽  
Vol 8 (3) ◽  
pp. 202056
Author(s):  
Md. Kausar Ahmed ◽  
Ajoy Kumer ◽  
Abu Bin Imran
Keyword(s):  
Click Reaction ◽  
Computational Study ◽  
Polymer Network ◽  
Cycloaddition Reaction ◽  
Polymeric Materials ◽  
High Yield ◽  
H Nmr ◽  
Facile Fabrication ◽  
Derivatives Of

Click reaction is a very fast, high yield with no by-product, biocompatible, tolerant to surrounded medium, and very specific cycloaddition reaction between azides and alkynes to form triazole. They are widely being employed in the synthesis of various polymeric materials. Here, the design, fabrication and characterization of hydrogel prepared using click reaction have been reported. At first, telechelic acetylene precursor for click reaction is prepared from diisocyanatohexane and propargyl alcohol in the presence of triethylamine. The azide derivatives of poly(hydroxyethylmethacrylate), i.e. poly(HEMA), are successfully prepared following two different routes. In route 1, esterification of bromopropionic acid is performed with HEMA monomer using N,N′- dicyclohexylcarbodiimide/4-dimethylaminopyridine (DCC/DMAP) as a catalyst followed by replacing bromide by azide moiety. Free radical polymerization of the fabricated monomer is then performed under N 2 atmosphere using azobisisobutyronitrile (AIBN) as an initiator. In route 2, polymerization of HEMA has been carried out first, then modification of the polymer with azide group via successive steps to obtain azide derivative polymer for click reaction. The hydrogel is prepared by a very fast, highly specific, and simple click reaction between azide derivative polymer and telechelic acetylene precursor using copper as a catalyst. The structures of derivatives of azide-functionalized HEMA, acetylene precursors and hydrogels are confirmed by FTIR and 1 H-NMR spectroscopy. The optimized structure of each precursor is determined, and their chemical and thermodynamic parameters are computationally studied in detail.

The formation of hex-5-enopyranosides and their selective hydrolysis in methylated polysaccharides

1978 ◽  
Vol 56 (5) ◽  
pp. 680-684 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Karl-Gunnar Rosell
Keyword(s):  
Uronic Acid ◽  
Gum Arabic ◽  
Hydroxyl Groups ◽  
Triphenyl Phosphite ◽  
Reaction Sequence ◽  
Selective Hydrolysis ◽  
Acidic Polysaccharides ◽  
Hydrolysis Of ◽  
Derivatives Of

The introduction of hex-5-enopyranoside residues into methylated acidic polysaccharides is effected by reduction of uronic acid residues, followed by reaction with triphenyl phosphite methiodide, and dehydroiodination. The selective hydrolysis of hex-5-enopyranosidic linkages with characterization of the 6-deoxyglycos-5-uloses thus formed and location of the aglyconic hydroxyl groups thus exposed has been demonstrated for methylated derivatives of birch xylan and gum arabic. The reaction sequence provides a new method for linkage analysis of acidic polysaccharides.

Comparative Studies of Brown Coal and Lignin. I. Infra-Red Spectra

1960 ◽  
Vol 13 (1) ◽  
pp. 156 ◽  
Author(s):  
RA Durie ◽  
BM Lynch ◽  
S Sternhell
Keyword(s):  
Brown Coal ◽  
Hydriodic Acid ◽  
Conclusive Evidence ◽  
Hydroxyl Groups ◽  
Infra Red ◽  
Aliphatic Ether ◽  
Derivatives Of ◽  
Alcoholic Hydroxyl ◽  
Chemical Evidence

The infra-red spectra of two softwood lignins are discussed with reference to the spectra of their acetyl and methoxyl derivatives. The spectra of the respective acetyl derivatives provide conclusive evidence for the presence of both phenolic and alcoholic groups in lignin and oxidized lignin, and of alcoholic groups only in the methoxyl derivatives of both these samples. Treatment of lignin with hydriodic acid in the conventional Zeisel determination of methoxyl groups eliminates the alcoholic hydroxyl groups and appears to split aliphatic ether linkages. The spectrum of lignin treated with hydriodic acid is very similar to that of brown coal, which supports previous chemical evidence that brown coal appears to be essentially " demethylated dehydrated lignin ". The progress of the isolation of lignin from wood was followed by infra-red spectroscopy.

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