In organic chemistry, a benzylidene acetal is the functional group with the structural formula C 6 H 5 CH(OR) 2 (R = alkyl, aryl). The set of model ethanol acceptors thus provides a simple and effective “toolbox” to investigate glycosylation reaction mechanisms and report on the robustness of glycosylation protocols.". 4,6-benzylidene acetal can be opened selectively under reductive conditions to yield either free 4-OH or 6-OH. The use of benzylidene acetals as protecting groups in carbohydrate chemistry is utterly important. endobj Carbohydrate acceptors are examined and the reactivity-selectivity profile of these nucleophiles mirrored those of the model acceptors studied. Results and discussion. It is revealed that the stereoselectivity in glycosylations of benzylidene protected glucose donors are very susceptible to acceptor nucleophilicity whereas condensations of benzylidene mannose and mannuronic acid donors represent more robust glycosylation systems in terms of diastereoselectivity. Powered by Pure, Scopus & Elsevier Fingerprint Engine™ © 2020 Elsevier B.V. We use cookies to help provide and enhance our service and tailor content. c1ccc(cc1)C2OC[[email protected]]([[email protected]@H](O2)[[email protected]@H]([[email protected]](C=O)O)O)O Dive into the research topics of 'The influence of acceptor nucleophilicity on the glycosylation reaction mechanism'. The 4,6-benzylidene acetal can be opened selectively, by a number of … AB - A set of model nucleophiles of gradually changing nucleophilicity is used to probe the glycosylation reaction mechanism.

While preparing the partially protected glucose 1 from α-allyl-4,6-benzylidene glucoside 2 (Scheme (Scheme1), 1), we observed that mono-benzylation could be achieved, if instead of DMF and the usual reagents' combination (i.e. The set of model ethanol acceptors thus provides a simple and effective “toolbox” to investigate glycosylation reaction mechanisms and report on the robustness of glycosylation protocols. S. Van der Vorm, T. Hansen, H. S. Overkleeft, G. A. I was assigned a project where I would help a few PhD candidates by protecting a few of the hydroxyl groups on D-glucose. <>/Subtype/Link/Rect[421 210 459.08 219]>> It is revealed that the stereoselectivity in glycosylations of benzylidene protected glucose donors are very susceptible to acceptor nucleophilicity whereas condensations of benzylidene mannose and mannuronic acid donors represent more robust glycosylation systems in terms of diastereoselectivity. 34 0 obj The influence of acceptor nucleophilicity on the glycosylation reaction mechanism. Benzylidene acetals and dimethyl acetals have thermodynamic tendency to form six- and five-membered rings, respectively. It is revealed that the stereoselectivity in glycosylations of benzylidene protected glucose donors are very susceptible to acceptor nucleophilicity whereas condensations of benzylidene mannose and mannuronic acid donors represent more robust glycosylation systems in terms of diastereoselectivity. The set of model ethanol acceptors thus provides a simple and effective “toolbox” to investigate glycosylation reaction mechanisms and report on the robustness of glycosylation protocols. That sounds about right, and something I was thinking of aswell, but I can't really get it right on paper. endobj The allylation one is fine, but the second one really bugs me. endobj and Cod{\'e}e, {J. D.C.}". endobj Please do not post entire problem sets or questions that you haven't attempted to answer yourself. The change in stereoselectivity with decreasing acceptor nucleophilicity is related to a change in reaction mechanism shifting from the SN2 side to the SN1 side of the reactivity spectrum. 31 0 obj

This should follow a simple mechanism similar to a typical acid-catalyzed ether synthesis (like this one). 35 0 obj

If borane is not activated, Lewis acid is the most electrophilic species that thus adds to O-6 and hence generates the 4-O-benzyl ether. UR - http://www.scopus.com/inward/record.url?scp=85014125732&partnerID=8YFLogxK, UR - http://www.scopus.com/inward/citedby.url?scp=85014125732&partnerID=8YFLogxK. Acetals are stable under basic and reductive conditions and unstable toward acids. The reaction: http://i.imgur.com/Zgtj6fZ.png. endobj Benzylidene acetals are used as protecting groups in glycochemistry. N2 - A set of model nucleophiles of gradually changing nucleophilicity is used to probe the glycosylation reaction mechanism. HO OH OH OH OH O O HO HO H H HO OH OH glucose O HO HO + HO OH α −D-glucose H β−D-glucose −D-g 37% trace amounts OH 63% Scheme 5.2 -­‐ The interconversion of cyclic to acyclic glucose Preparation of a cyclic acetal In this experiment, you will create a benzylidene acetal at the C4 and C6 alcohols of glucose, creating a “protected” glucose via transglycosylation. Either pointing me to litterature that shows the mechanism, or got an idea of how to write it? CopyCopied, CSID:129940, http://www.chemspider.com/Chemical-Structure.129940.html (accessed 17:09, Nov 12, 2020) <>/Subtype/Link/Rect[308.78 516.5 385.81 523.5]>> <>/Subtype/Link/Rect[456.1 275 471.34 284]>> Log Octanol-Water Partition Coef (SRC): Log Kow (KOWWIN v1.67 estimate) = -0.22 Boiling Pt, Melting Pt, Vapor Pressure Estimations (MPBPWIN v1.42): Boiling Pt (deg C): 430.17 (Adapted Stein & Brown method) Melting Pt (deg C): 162.14 (Mean or Weighted MP) VP(mm Hg,25 deg C): 1.4E-010 (Modified Grain … Press J to jump to the feed. <>/Subtype/Link/Rect[121.09 184 138.35 193]>> Three different glycosylation systems were scrutinized, that differ in the reaction mechanism, that-putatively-prevails during the coupling reaction. <>/Subtype/Link/Rect[233.23 210 251.51 219]>> Acetal formation is generally thought to go through oxocarbenium ions and addition to those rather than an SN2 mechanism, New comments cannot be posted and votes cannot be cast. This is apparently a thing now that people are writing exams from home. 1.06.4.3.3 Regioselective hydrogenolysis of dioxane- and dioxolane-type benzylidene acetals 235 1.06.4.3.4 Hydrogenolysis of molecules carrying dioxane and dioxolane rings 236 1.06.4.3.5 Hydrogenolysis of symmetrical ketals 237 1.06.4.3.6 Oxidative cleavage of dioxane- and dioxolane-type benzylidene acetals 241 1.06.5 Protection of Amine 242 endobj I've been using some time to try to find out one for myself aswell. <>/Subtype/Link/Rect[279.34 210 289.98 219]>> 32 0 obj The change in stereoselectivity with decreasing acceptor nucleophilicity is related to a change in reaction mechanism shifting from the SN2 side to the SN1 side of the reactivity spectrum.

<>/Subtype/Link/Rect[82.83 197 93.34 206]>> Glycosylations of ethanol-based acceptors, bearing varying amounts of fluorine atoms, report on the dependency of the stereochemistry in condensation reactions on the nucleophilicity of the acceptor. abstract = "A set of model nucleophiles of gradually changing nucleophilicity is used to probe the glycosylation reaction mechanism. It is revealed that the stereoselectivity in glycosylations of benzylidene protected glucose donors are very susceptible to acceptor nucleophilicity whereas condensations of benzylidene mannose and mannuronic acid donors represent more robust glycosylation systems in terms of diastereoselectivity. By continuing you agree to the use of cookies, Vrije Universiteit Amsterdam data protection policy.

I guess it's somehow basic acid-catalysed substitution with CH3OH as a leaving group, but I can't seem to make it fit. Carbohydrate acceptors are examined and the reactivity-selectivity profile of these nucleophiles mirrored those of the model acceptors studied. endobj author = "{Van der Vorm}, S. and T. Hansen and Overkleeft, {H. S.} and {Van der Marel}, {G. endobj Does anyone know how to go about it? So I'm doing a project in my Advanced Organic lab course. The most important protecting groups in carbohydrate chemistry are reviewed. <>/Subtype/Link/Rect[125.37 476.5 230.06 483.5]>>

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