Stereoelectronic Model To Explain Highly Stereoselective Reactions of Seven‐Membered‐Ring Oxocarbenium‐Ion Intermediates

Beaver, Matthew G.; Buscagan, Trixia M.; Lavinda, Olga; Woerpel, K. A.

doi:10.1002/anie.201507806

Cited by 21 publications

(26 citation statements)

References 30 publications

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“…Glycosylation of n ‐octanol similarly yielded 26 and 28 as the major products in moderate yields (36 % and 43 %) with the β‐glycoside as a major product in both the cases . In the case of the Koenigs–Knorr and iodine mediated glycosylations, reactions proceeded through some version of cyclic oxocarbenium intermediate formed due to removal of bromide anion . The intermediate was then presumably trapped with the incoming nucleophile to deliver the products selectively.…”

Section: Resultsmentioning

confidence: 98%

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

et al. 2018

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Protein–carbohydrate interactions are at the heart of many biological processes. For lectins, those interactions result simply in the association of two species, whereas for enzymes like glycosidases, association ultimately leads to cleavage and formation of covalent bonds. We have investigated lectin–septanose interactions in the past. Here we report on a route to synthesize p‐nitrophenyl septanosides via the corresponding septanosyl halides. During the investigation we observed differential rates of glycosyl halide formation of the per‐O‐acetyl septanoses based on the stereochemistry at C1 and C2. Further, we observed unexpected stereoselectivities in glycoside bond formation that depended on a number of factors including the electrophilic sugar species, the incoming nucleophile, and reaction conditions. The results provided new parameters to consider when approaching septanose glycosylations. Even more importantly, the synthesis of p‐nitrophenyl septanosides will enable them to be used to interrogate septanose‐glycosidase binding and hydrolysis.

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Section: Resultsmentioning

confidence: 98%

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

et al. 2018

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“…A comparable inside attack model also has been used to rationalize the facial selectivity of simple nucleophiles for seven-membered cyclic oxocarbenium ions of possible relevance to the septanosides …”

Section: Facial Selectivity Of Nucleophilic Attack On Putative Glycos...mentioning

confidence: 97%

The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface

et al. 2018

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A critical review of the state-of-the-art evidence in support of the mechanisms of glycosylation reactions is provided. Factors affecting the stability of putative oxocarbenium ions as intermediates at the S1 end of the mechanistic continuum are first surveyed before the evidence, spectroscopic and indirect, for the existence of such species on the time scale of glycosylation reactions is presented. Current models for diastereoselectivity in nucleophilic attack on oxocarbenium ions are then described. Evidence in support of the intermediacy of activated covalent glycosyl donors is reviewed, before the influences of the structure of the nucleophile, of the solvent, of temperature, and of donor-acceptor hydrogen bonding on the mechanism of glycosylation reactions are surveyed. Studies on the kinetics of glycosylation reactions and the use of kinetic isotope effects for the determination of transition-state structure are presented, before computational models are finally surveyed. The review concludes with a critical appraisal of the state of the art.

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“…The origin of the other stereoisomer was not explained, however. The sense of is similar to the selectivity observed for reactions of structurally similar seven-membered-ring oxocarbenium ions, whose reactions are likely controlled by stereoelectronic and torsional effects …”

Section: Additions Of Allylmagnesium Reagents To Imines and Related S...mentioning

confidence: 99%

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin–Anh and Chelation-Control Models

et al. 2020

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This review describes the additions of allylmagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reagents. In many cases, allylmagnesium reagents either react with low stereoselectivity when other Grignard reagents react with high selectivity, or allylmagnesium reagents react with the opposite stereoselectivity. This review collects hundreds of examples, discusses the origins of stereoselectivities or the lack of stereoselectivity, and evaluates why selectivity may not occur and when it will likely occur. CONTENTS 4.2.5. Additions to β-Substituted Aldehydes 4.2.6. Additions to Aldehydes with Distant Chelating Groups 4.3. Additions to Cyclic Ketones 4.3.1. Alkoxy-Substituted Cyclic Ketones 4.3.2. Additions to Alkoxy-Substituted Five-Membered-Ring Ketones 4.3.3. Additions to Alkoxy-Substituted Four-Membered-Ring Ketones 4.4. Additions of Allylmagnesium Halides to Cyclic Hemiacetals 5. Diastereoselectivity of Reactions of Allylmagnesium Reagents with Carbonyl Compounds by Felkin−Anh Control 5.1. Felkin−Anh Stereoselectivity 5.2. Additions to α-Chiral Acyclic Ketones 5.3. Additions to Chiral Exocyclic Ketones and Aldehydes 5.4. Additions of Allylmagnesium Halides to Chiral Cyclic Ketones Controlled by Felkin−Anh Selectivity 5.5. Additions of Allylmagnesium Halides to Chiral Acyclic Aldehydes 6. Diastereoselectivity of Reactions with Carbonyl Compounds by Steric Approach Control 6.1. Steric Approach Control and Stereoselectivity

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Stereoelectronic Model To Explain Highly Stereoselective Reactions of Seven‐Membered‐Ring Oxocarbenium‐Ion Intermediates

Cited by 21 publications

References 30 publications

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin–Anh and Chelation-Control Models

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Stereoelectronic Model To Explain Highly Stereoselective Reactions of Seven‐Membered‐Ring Oxocarbenium‐Ion Intermediates

Cited by 21 publications

References 30 publications

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

The Experimental Evidence in Support of Glycosylation Mechanisms at the SN1–SN2 Interface

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin–Anh and Chelation-Control Models

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The Experimental Evidence in Support of Glycosylation Mechanisms at the S_N1–S_N2 Interface