Photosensitive protecting groups of amino sugars and their use in glycoside synthesis. 2-Nitrobenzyloxycarbonylamino and 6-nitroveratryloxycarbonylamino derivatives

1974 ◽  
Vol 39 (2) ◽  
pp. 192-196 ◽  
Author(s):  
Boaz Amit ◽  
Uri Zehavi ◽  
Abraham Patchornik
Keyword(s):  
Protecting Groups ◽  
Amino Sugars ◽  
Glycoside Synthesis

Glycosynthases: Mutant Glycosidases for Glycoside Synthesis

2002 ◽  
Vol 55 (2) ◽  
pp. 3 ◽  
Author(s):  
S. J. Williams ◽  
S. G. Withers
Keyword(s):  
Substrate Specificity ◽  
Product Formation ◽  
Protecting Groups ◽  
Rapid Screening ◽  
Widespread Application ◽  
Glycoside Synthesis ◽  
General Methodology ◽  
Glycosyl Donor ◽  
Substrate Variation ◽  
Catalytic Power

Glycosynthases are engineered mutant glycosidases that catalyse the formation of a glycosidic bond from a glycosyl donor and an acceptor alcohol. They are constructed by mutation of the enzymic nucleophile of a retaining glycosidase to a small non-nucleophilic residue. To date, five glycosynthases have been reported capable of synthesizing a range of β-glycosidic linkages. Methods to integrate protecting groups into glycosynthase-mediated glycosylations have been developed that broaden their applicability and enable finer control over product formation. Mutagenesis studies have improved the catalytic power of the original Abg glycosynthase, and a general methodology has been developed that allows the rapid screening of libraries of mutant glycosynthases for catalysts with improved activity. A method for determining aglycon substrate specificity has been developed to define the limits of substrate variation tolerated by a parent glycosidase and thence the derived glycosynthase. Together, these developments portend a bright future for the discovery of new glycosynthases and their widespread application as catalysts to assist in the rapid and efficient assembly of complex glycoconjugates.

Synthesis of 6-O-octyl-β-D-galactopyranosyl-(1 → 5)-L-arabinose and comparative 1-deoxyglycitolation of Nα-Z-L-lysine with amphiphilic lipodisaccharides

1990 ◽  
Vol 68 (12) ◽  
pp. 2253-2257 ◽  
Author(s):  
Daniel Cabaret ◽  
Michel Wakselman
Keyword(s):  
Chemical Modification ◽  
Organic Solvents ◽  
Future Study ◽  
Acyl Transfer ◽  
Protecting Groups ◽  
Reductive Alkylation ◽  
Glycoside Synthesis ◽  
Mild Conditions ◽  
Chemical Modification Of Enzymes

A lipodisaccharide possessing a reactive aldopentose unit, 6-O-octyl-β-D-galactopyranosyl-(1 → 5)-L-arabinose 6, was obtained by glycoside synthesis. To avoid a possible intramolecular acyl transfer, benzoyl protecting groups and mild conditions of detritylation were used in the preparation of the furanosyl acceptor. The reductive alkylation of Nα-Z-L-lysine was then studied and compared to that of previously prepared liposaccharides. In this reaction, amphiphilic five-membered hemiacetals are generally more reactive than their six-membered analogues. The newly prepared disaccharide is the most reactive of the series and also the easiest to prepare. Therefore this reagent has been selected for a future study on the chemical modification of enzymes and the use in organic solvents of the biocatalysts obtained. Keywords: liposaccharides, reductive alkylation.

Visible Light-Mediated Oxidative Debenzylation

2020 ◽  
Author(s):  
Cristian Cavedon ◽  
Eric T. Sletten ◽  
Amiera Madani ◽  
Olaf Niemeyer ◽  
Peter H. Seeberger ◽  
...  
Keyword(s):  
Reaction Time ◽  
Visible Light ◽  
Functional Groups ◽  
Continuous Flow ◽  
Protecting Groups ◽  
Benzyl Ether ◽  
Complex Molecules ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

2019 ◽  
Vol 16 (12) ◽  
pp. 955-958
Author(s):  
Reddymasu Sireesha ◽  
Reddymasu Sreenivasulu ◽  
Choragudi Chandrasekhar ◽  
Mannam Subba Rao
Keyword(s):  
Room Temperature ◽  
Protecting Groups ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Acid Sensitivity ◽  
Time Period ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Last Stage ◽  
Zinc Triflate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

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