Synthesis and <sup>13</sup>C NMR Spectroscopy of Model Compounds for the Microstructure Analysis of Poly(Vinyl Glycoside)s

Yuan, Jie; Frauenrath, Holger

doi:10.1002/ejoc.200800798

Cited by 4 publications

(1 citation statement)

References 32 publications

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“…The simplistic model (see Figure ), which prompted this study, was partly based on the idea that the remaining degrees of freedom of the MCPM group would be identical and hence the chirality would exhibit itself by reversing the relative positions of the two smallest groups, namely the methyl and the hydrogen. A previous study of chiral at the aglycone carbon of mannosides found this to be true with both isomers having the largest group anti . However, our recent study of the neutral mannosides with MCPM at the anomeric center found that the Ψ(C-1–O-1–C(MCPM)–C(Cp) torsion angle had different minima .…”

Section: Resultsmentioning

confidence: 74%

Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions?

Kumar

Whitfield

2012

J. Org. Chem.

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Although long postulated, the existence of glycopyranosyl oxacarbenium ions as intermediates or transition states (TS) in chemical glycosylation reactions has not been convincingly demonstrated experimentally. It is anticipated that elucidation of such reactive species will greatly assist synthetic chemists to control the α/β stereoselectivity by rational means. Previous density functional theory (DFT) calculations from our group found that the torsion potential about C-2-O-2 in protected glycopyranosyl donors changed from a conventional 3-fold rotor to a 2-fold rotor with a strong syn (CH-2-C-2-O-2-CPg) preference once the donor was ionized to its oxacarbenium ion. This suggested to us that if CPg of the protecting group was a chiral carbon, then diastereoselectivity might be observed in glycosylation reactions that proceed through oxacarbenium ions. The hypothesis to test is as follows: if a nonparticipating O-2 racemic chiral protecting group exhibits diastereoselectivity in glycosylation reactions, then the reaction probably proceeds through an oxacarbenium ion intermediate or TS. We present data for O-2 ether-protected d-glucopyranosyl donors where the racemic protecting group 1-methyl 1'-methylcyclopropylmethyl (MCPM) provides the chirality. MCPM proves to be more activating than the O-2-benzyl ether, and in cases where the donor is otherwise deactivated, several examples of moderate diastereoselectivity are found. These results can be interpreted to indicate that a continuum of reactivity exists where some glycosyl donors form oxacarbenium ions in glycosylation reactions but more reactive donors do not. The strongly activating properties of the cyclopropylmethyl ether functionality and the ability to induce diastereoselectivity with chiral derivatives strongly suggest widespread applications.

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Section: Resultsmentioning

confidence: 74%

Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions?

Kumar

Whitfield

2012

J. Org. Chem.

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Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2009–2010

Harvey

2014

Mass Spectrometry Reviews

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This review is the sixth update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2010. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, arrays and fragmentation are covered in the first part of the review and applications to various structural typed constitutes the remainder. The main groups of compound that are discussed in this section are oligo and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Many of these applications are presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis.

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1-Methyl 1′-cyclopropylmethyl (MCPM) as an anomeric protecting group

Whitfield

2011

Tetrahedron

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Synthesis and ¹³C NMR Spectroscopy of Model Compounds for the Microstructure Analysis of Poly(Vinyl Glycoside)s

Cited by 4 publications

References 32 publications

Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions?

Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions?

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2009–2010

1-Methyl 1′-cyclopropylmethyl (MCPM) as an anomeric protecting group

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Synthesis and 13C NMR Spectroscopy of Model Compounds for the Microstructure Analysis of Poly(Vinyl Glycoside)s

Cited by 4 publications

References 32 publications

Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions?

Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions?

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2009–2010

1-Methyl 1′-cyclopropylmethyl (MCPM) as an anomeric protecting group

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Synthesis and ¹³C NMR Spectroscopy of Model Compounds for the Microstructure Analysis of Poly(Vinyl Glycoside)s