Conformationally superarmed S-ethyl glycosyl donors as effective building blocks for chemoselective oligosaccharide synthesis in one pot

Bandara, Mithila D.; Yasomanee, Jagodige P.; Rath, Nigam P.; Pedersen, Christian; Bols, Mikael; Demchenko, Alexei V.

doi:10.1039/c6ob02498j

Cited by 11 publications

(17 citation statements)

References 37 publications

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“…The influence of the protecting groups has been studied widely in reference to glycosylation reactions and is in accordance with recent reports that side group orientation plays a significant role in tuning reactivity. 58,60,74,75 In particular, our findings align with those of Bols and coworkers that the bulky silyl groups increase the population of the ring-flipped conformers with substituents in the axial position ( 5 H 4 ), thereby modulating reactivity. 74 For example, a single silyl group on the 6′-OH of 11 and 12 increases the predominance of the pseudo-axial conformation leading to a significant acceleration in reactivity in parallel with higher calculated alkene energy.…”

Section: ■ Conclusionsupporting

confidence: 90%

Guidelines for β-Lactam Synthesis: Glycal Protecting Groups Dictate Stereoelectronics and [2+2] Cycloaddition Kinetics

et al. 2020

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The alkene-isocyanate cycloaddition method affords β-lactams from glycals with high regio- and stereoselectivity, but the factors that determine substrate reactivity are poorly understood. Thus, we synthesized a library of 17 electron-rich alkenes (glycals) with varied protecting groups to systematically elucidate the factors that influence their reactivity toward the electron-poor trichloroacetyl isocyanate. The experimentally determined reaction rates exponentially correlate with the computationally determined highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap and natural bond orbital (NBO) valence energies. The electron-withdrawing ability of the protecting groups, but not bulk, impacts the electron density of the glycal allyloxocarbenium system when oriented pseudo-axially (i.e., stereoelectronics). In this conformation, ring σC–O* orbitals oriented antiperiplanar to the allyloxocarbenium system decrease glycal reactivity via negative hyperconjugation as protecting group electron withdrawal increases. Transition-state calculations reveal that protecting group stereoelectronics direct the reaction to proceed via an asynchronous one-step mechanism through a zwitterionic species. The combined experimental and computational findings, along with experimental validation on an unknown glycal, provide insight on the reaction mechanism and the role of distant protecting groups in glycal reactivity. Together, these studies will aid in the synthesis of new β-lactam antibiotics, β-lactamase inhibitors, and bicyclic carbohydrate-β-lactam monomers prepared by the alkene-isocyanate method.

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Section: ■ Conclusionsupporting

confidence: 90%

Guidelines for β-Lactam Synthesis: Glycal Protecting Groups Dictate Stereoelectronics and [2+2] Cycloaddition Kinetics

et al. 2020

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“…The concept of the conformational superarming developed by Bols et al 287,288 was also applied to a one-pot synthesis with all three reaction components present from the beginning. 287,384…”

Section: Traditional Manual Synthesis Of Oligosaccharidesmentioning

confidence: 99%

Automated Chemical Oligosaccharide Synthesis: Novel Approach to Traditional Challenges

et al. 2018

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Advances in carbohydrate chemistry have certainly made common oligosaccharides much more accessible. However, many current methods still rely heavily upon specialized knowledge of carbohydrate chemistry. The application of automated technologies to chemical and life science applications such as genomics and proteomics represents a vibrant field. These automated technologies also present opportunities for their application to organic synthesis, including that of the synthesis of oligosaccharides. However, application of automated methods to the synthesis of carbohydrates is an underdeveloped area as compared to other classes of biomolecules. The overarching goal of this review article is to present the advances that have been made at the interface of carbohydrate chemistry and automated technology.

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“…30 The anchimeric activation by the neighboring group effect was smaller than the effect from the extra TBS group. 31…”

Section: Account Synlettmentioning

confidence: 99%

Silylated Sugars – Synthesis and Properties

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Pedersen

et al. 2021

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Silicon has been used in carbohydrate chemistry for half a century, but mostly as a protective group for sugar alcohols. Recently, the use of silicon has expanded to functionalization via C–H activation, conformational arming of glycosyl donors, and conformational alteration of carbohydrates. Silicon has proven useful as more than a protective group and during the last one and a half decades we have demonstrated how it influences both the reactivity of glycosyl donors and stereochemical outcome of glycosylations. Silicon can also be attached directly to the sugar C-backbone, which has even more pronounced effects on the chemistry and properties of the molecules. In this Account, we will give a tour through our work involving silicon and carbohydrates.1 Introduction2 Conformational Arming of Glycosyl Donors with Silyl Groups3 Silyl Protective Groups for Tethering Glycosyl Donors4. Si–C Glycosides via C–H Activation4.1 C–H Activation and Oxidation of Methyl 6-Deoxy-l-glycosides4.2 Synthesis of All Eight 6-Deoxy-l-sugars4.3 Synthesis of All Eight l-Sugars by C–H Activation4.4 Modification of the Oxasilolane Ring5 C–Si in Glycosyl Donors – Activating or Not?6 Si–C-Substituted Pyranosides7 Perspective

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Conformationally superarmed S-ethyl glycosyl donors as effective building blocks for chemoselective oligosaccharide synthesis in one pot

Cited by 11 publications

References 37 publications

Guidelines for β-Lactam Synthesis: Glycal Protecting Groups Dictate Stereoelectronics and [2+2] Cycloaddition Kinetics

Guidelines for β-Lactam Synthesis: Glycal Protecting Groups Dictate Stereoelectronics and [2+2] Cycloaddition Kinetics

Automated Chemical Oligosaccharide Synthesis: Novel Approach to Traditional Challenges

Silylated Sugars – Synthesis and Properties

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