scholarly journals Synthesis of carbohydrate building blocks via regioselective uniform protection/deprotection strategies

2019 ◽  
Vol 17 (20) ◽  
pp. 4934-4950 ◽  
Author(s):  
Tinghua Wang ◽  
Alexei V. Demchenko
Keyword(s):  
Building Blocks ◽  
Hydroxyl Group ◽  
Free Hydroxyl

Scope 1: sugar is uniformly protected leaving only one (or two) free hydroxyl group; scope 2: uniformly protected sugar is deprotected to liberate only one (or two) hydroxyl group.

scholarly journals Preparation of a set of selectively protected disaccharides for modular synthesis of heparan sulfate fragments: toward the synthesis of several O-sulfonated [β-D-GlcUA-(1→4)-β-D-GlcNAc]OPr types

2005 ◽  
Vol 3 (4) ◽  
pp. 803-829 ◽  
Author(s):  
Hammed Hassan
Keyword(s):  
Heparan Sulfate ◽  
Building Blocks ◽  
Protecting Groups ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Allyl Ethers ◽  
Modular Synthesis ◽  
Stereocontrolled Synthesis ◽  
Benzyl Ethers ◽  
Free Hydroxyl

AbstractA concise method for a stereocontrolled synthesis of a set of selectively protected disaccharides is reported. Coupling of the donor 11 onto acceptors 23 and 24, promoted by trimethylsilyl triflate-N-iodosuccinimide (TMSOTf-NIS), generated the disaccharides 25 and 26. Under typical conditions, condensation of the fully protected donor 12 onto acceptors 23 and 24 produced the disaccharides 27 and 28. The building blocks 25–28 were prepared in moderate yields having exclusive β-stereoselectivity. A unique pattern of protecting groups distinguished clearly between positions to be sulfated and functional groups remaining as free hydroxyl groups. Acetyl and/or levulinoyl esters temporarily protected the positions to be sulfated, while benzyl ethers were used for permanent protection. The anomeric positions were protected as allyl ethers, whereas the 4′-positions were masked as p-methoxybenzyl (PMB) ethers. The orthogonality of the PMB and allyl groups can then be used for further elongation of the chain by recurrent deprotection and activation steps. The hydroxyl group, OH-6, of glucosamine moieties was protected as a TBDPS ether to avoid oxidation. A five-step deprotection/sulfonation sequence was applied to the disaccharide 27 to generate the corresponding sulfated [β-D-GlcUA-2-OSO3Na-(1→4)-β-D-Glc pNAc]-(1→O-Pro) 34.

scholarly journals Studies on the formation of complex oxidation and condensation products of phenols. Part III. -Rearrangements of oxidation-reduction type in the diquinone group

1933 ◽  
Vol 143 (848) ◽  
pp. 223-228 ◽  
Keyword(s):  
Hydroxyl Group ◽  
Hydrogen Atoms ◽  
Blue Colour ◽  
Highly Active ◽  
Oxidation Reduction ◽  
Intramolecular Reactions ◽  
Trimethyl Ether ◽  
Free Hydroxyl ◽  
Ethereal Oxygen ◽  
Complex Oxidation

The diquinones have been but little investigated, and as they contain two condensed highly active quinonid systems it is to be anticipated that they should be capable of interesting intramolecular reactions. When heated to 210-215º, 4 : 4'-dimethoxydiquinone is rapidly converted into a red crystalline isomeride (yield, 90%), soluble in alkali with an intense blue colour, and yielding a mono-acetate indicating the occurrence of a free hydroxyl group. Two hydrogen atoms are taken up on reduction, and the phenolic product yields a triacetate and a trimethyl ether. It follows that of the four carbonyl oxygens of 4 : 4'-dimethoxydiquinone, one has been converted into a hydroxyl group, and another which does not exhibit any functional activity, is probably present as ethereal oxygen. These results led to formula (III) as representing the product of rearrangement.

scholarly journals Synthesis and Characterizations of Dipeptide Derivative of Gentamicin

2019 ◽  
Vol 28 (2) ◽  
pp. 73-82
Author(s):  
Oun D. Khudair ◽  
Diar A. Fatih
Keyword(s):  
Acid Chloride ◽  
Solution Method ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Ester Linkage ◽  
Amine Groups ◽  
Conventional Solution ◽  
Dipeptide Derivative

Abstract       The target derivative are gentamicin linked with L-Val- L-Ala by an ester linkage. These were synthesized by esterification method, which included the reaction of -OH hydroxyl group on (carbon No.5) of gentamicin with the acid chloride of the corresponding dipeptide, The preparation of new derivative of gentamicin involved protected the primary & secondary amine groups of Gentamicin, by Ethylchloroformate (ECF) to give N-carbomethoxy Gentamicin which was used for further chemical synthesis involving the free hydroxyl groups. Then prepared dipeptide (L-Val- L-Ala) by conventional solution method in present DCC & HoBt then reacted with thionyl chloride to prepared acid chloride of dipeptides, then after, linked by ester linkage to N-protection gentamicin in present pyridine as base, finally deportation the amino group of synthesized compound by using TFAA in present anisole. The characterization of the titled compounds were performed utilizing FTIR spectroscopy, CHNS elemental analysis, and by measurements of their physical properties.  

scholarly journals Electronically Excited States of Potential Interstellar, Anionic Building Blocks for Astrobiological Nucleic Acids

2021 ◽  
Vol 8 ◽  
Author(s):  
Taylor J. Santaloci ◽  
Marie E. Strauss ◽  
Ryan C. Fortenberry
Keyword(s):  
Nucleic Acids ◽  
Excited States ◽  
Lone Pair ◽  
Building Blocks ◽  
Hydroxyl Group ◽  
Quantum Chemical Analysis ◽  
Electronically Excited States ◽  
Neutral Radical ◽  
Electronically Excited ◽  
Electron Withdrawing Group

Functionalizing deprotonated polycyclic aromatic hydrocarbon (PAH) anion derivatives gives rise to electronically excited states in the resulting anions. While functionalization with −OH and −C2H, done presently, does not result in the richness of electronically excited states as it does with −CN done previously, the presence of dipole-bound excited states and even some valence excited states are predicted in this quantum chemical analysis. Most notably, the more electron withdrawing −C2H group leads to valence excited states once the number of rings in the molecule reaches three. Dipole-bound excited states arise when the dipole moment of the corresponding neutral radical is large enough (likely around 2.0 D), and this is most pronounced when the hydrogen atom is removed from the functional group itself regardless of whether functionalized by a hydroxyl or enthynyl group. Deprotonatation of the hydroxyl group in the PAH creates a ketone with a delocalized highest occupied molecular orbital (HOMO) unlike deprotonation of a hydrogen on the ring where a localized lone pair on one of the carbon atoms serves as the HOMO. As a result, hydroxyl functionlization and subsequent deprotonation of PAHs creates molecules that begin to exhibit structures akin to nucleic acids. However, the electron withdrawing −C2H has more excited states than the electron donating −OH functionalized PAH. This implies that the −C2H electron withdrawing group can absorb a larger energy range of photons, which signifies an increasing likelihood of being stabilized in the harsh conditions of the interstellar medium.

Isohexide hydroxy esters: synthesis and application of a new class of biobased AB-type building blocks

RSC Advances ◽  
2014 ◽  
Vol 4 (89) ◽  
pp. 47937-47950 ◽  
Author(s):  
Shanmugam Thiyagarajan ◽  
Jing Wu ◽  
Rutger J. I. Knoop ◽  
Jacco van Haveren ◽  
Martin Lutz ◽  
...  
Keyword(s):  
Methyl Ester ◽  
Building Blocks ◽  
Ester Group ◽  
Hydroxyl Group ◽  
Secondary Hydroxyl ◽  
New Class ◽  
New Family ◽  
Hydroxy Esters

Here we present the synthesis of a new family of sugar derived 1,4:3,6-dianhydrohexitol based AB-type monomers, containing one methyl ester group and a secondary hydroxyl group in all four possible stereo isomers (RR, RS, SR, SS).

Hierarchial Structure and Physical Properties of Natural Cellulosic Fibers

1991 ◽  
Vol 255 ◽  
Author(s):  
Ludwig Rebenfeld
Keyword(s):  
Building Blocks ◽  
Decomposition Temperature ◽  
Fiber Axis ◽  
Hydroxyl Groups ◽  
Wood Fibers ◽  
Cellulosic Fibers ◽  
Naturally Occurring ◽  
Specific Source ◽  
Free Hydroxyl ◽  
Intramolecular Hydrogen

AbstractNatural cellulosic fibers have in common the fact that cellulose is the key polymeric component in the structure, although the chemical composition varies widely depending on the specific source of the fibers. Cellulose is a long-chain linear condensation polymer of β-D-glucose with three free hydroxyl groups on each monomeric unit, resulting in strong inter- and intramolecular hydrogen bonds. Because of the hydrogen bond network, and also due to restricted rotation around the polymeric 1,4- β-linkage, cellulose is a rigid and stiff chain with a Tg well above the chemical decomposition temperature.Despite the high Tg native cellulose is invariably highly crystalline as a result of the biosynthetic process. In naturally occurring cellulosic fibers, the cellulose crystallites are aggregated into fibrils which constitute the underlying building blocks of the fiber. In cotton, the fibrils are laid down during the development or growth of the fiber in the form of concentric layers. The fibrils are disposed at an angle of 23° with respect to the fiber axis and thus they describe a helical pattern. The sense of the helix reverses frequently along the length of the fiber. This morphology is unique to cotton; other cellulosic fibers such as ramie and jute have similar fibrillar structures, but fibrillar angles in the 5 to 10 degree range, with no reversals. Wood fibers, on the other hand, are structurally more heterogeneous and may be considered as composites.

scholarly journals Improvement of Naturally Derived Food Colorant Performance with Efficient Pyranoanthocyanin Formation from Sambucus nigra Anthocyanins Using Caffeic Acid and Heat

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5998
Author(s):  
Nicole Straathof ◽  
M. Monica Giusti
Keyword(s):  
Caffeic Acid ◽  
Hydroxyl Group ◽  
Effect Of Temperature ◽  
Red Wines ◽  
Plant Pigments ◽  
Sambucus Nigra ◽  
Molar Ratios ◽  
Free Hydroxyl ◽  
Compositional Changes ◽  
C 50

Consumers and regulations encourage the use of naturally derived food colorants. Anthocyanins (ACN), plant pigments, are unstable in foods. In aged red wines, ACN with a free hydroxyl group at C-5 condenses to form pyranoanthocyanins (PACN), which are more stable but form inefficiently. This study attempted to produce PACN efficiently using high cofactor concentration and heat. Elderberry anthocyanins were semi-purified and caffeic acid (CA) was dissolved in 15% ethanol and diluted with a buffer to achieve ACN:CA molar ratios of 1:50, 1:100, 1:150, and 1:200, then incubated at 65 °C for 5 days. The effect of temperature was tested using ACN samples incubated with or without CA at 25 °C, 50 °C, and 75 °C for 7 days. Compositional changes were monitored using uHPLC-PDA-MS/MS. Higher CA levels seemed to protect pigment integrity, with ACN:CA 1:150 ratio showing the highest tinctorial strength after 48 h. PACN content growth was fastest between 24 and 48 h for all ACN:CA ratios and after 120 h, all ACN had degraded or converted to PACN. PACN formed faster at higher temperatures, reaching ~90% PACN in 24 h and ~100% PACN in 48 h at 75 °C. These results suggest that PACN can form efficiently from elderberry ACN and CA if heated to produce more stable pigments.

Growth Inhibitory Properties of Synthetic Chalcones

2020 ◽  
Vol 16 (6) ◽  
pp. 892-899
Author(s):  
Gajanan D. Kottapalle ◽  
Nagesh J. Deshmukh ◽  
Avinash T. Shinde
Keyword(s):  
Antibacterial Activity ◽  
Condensation Reaction ◽  
Aromatic Aldehydes ◽  
Hydroxyl Group ◽  
Diffusion Method ◽  
Bacillus Species ◽  
Interesting Insight ◽  
Growth Inhibitory ◽  
Free Hydroxyl ◽  
Target Molecules

Background: In the present study, chalcones were synthesized from 2-hydroxy-1- acetonaphthone and substituted aromatic aldehydes were synthesized by Claisen Schmidt condensation reaction using potassium hydroxide as a base. The synthesized chalcones were purified by recrystallization from ethanol and evaluated for antibacterial activity by well diffusion method. The antibacterial activity was evaluated against Bacillus licheniformis, Bacillus species, Escherichia coli and Staphylococcus aureus using Ciprofloxacin as a standard. Methods: The target molecules were prepared by reacting 2-hydroxy-1-acetonaphthone and various substituted aromatic aldehyde in the presence of suitable condensing agents. The structure of synthesized compounds was confirmed on the basis of elemental analysis, IR, 1H NMR and 13C NMR spectral data. These synthesized compounds were also screened for antibacterial activity. Results: In the present study, free hydroxyl group in position 2 or 4 of aldehyde ring of synthesized chalcones appears to be a very important requirement in increasing the activity (2-5 and 8-13). When the hydroxyl group in position 4 is alkylated (14, 15), the chalcones become less active. When more complex substituent is present on the aldehyde ring (6, 7) there is a decrease in the activity. Conclusion: Newly synthesized chalcones (1-15) show good and moderate antibacterial activity. We believe that the new hydroxy substituted (in aldehyde ring) chalcones (2-5 and 8-13) reported in this work may provide an interesting insight for further optimization.

Investigations into the decomposition of aminoacyl-substituted monosaccharide scaffolds from a drug discovery library

2015 ◽  
Vol 13 (13) ◽  
pp. 4070-4079 ◽  
Author(s):  
Q. Q. He ◽  
N. Wimmer ◽  
G. Verquin ◽  
W. Meutermans ◽  
V. Ferro
Keyword(s):  
Drug Discovery ◽  
Acyl Transfer ◽  
Hydroxyl Group ◽  
Side Chain ◽  
Free Hydroxyl ◽  
Acidic Conditions

Decomposition of aminoacyl-substituted d-galactoside scaffolds under acidic conditions is dependent on the length of the side chain and is accelerated by the presence of a free hydroxyl group at C-6. In the latter case, evidence is provided that the reaction occurs via an N- to O-acyl transfer.

Metal-free hydroxyl functionalized quaternary phosphine type ionic liquids polymer for cycloaddition of CO2 and epoxide

2021 ◽  
Author(s):  
Wuying Zhang ◽  
Qian He ◽  
Yaju Chen ◽  
Rongchang Luo ◽  
Xiantai Zhou ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Synergistic Effect ◽  
Hydroxyl Group ◽  
Brønsted Acidity ◽  
Metal Free ◽  
Brönsted Acidity ◽  
Free Hydroxyl ◽  
Alkylation Reactions

Quaternary phosphine type hypercrosslinked polymer catalysts were successfully fabricated with the Friedel-Crafts alkylation reactions, benefit from synergistic effect between the Brönsted acidity of the hydroxyl group and nucleophilic of the...

Sign in / Sign up

Export Citation Format

Share Document