Oxazolinium ion

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• Author: Spencer Williams
• Responsible Curator: Spencer Williams

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An oxazolinium ion is the species that is formed by anchimeric assistence in the glycosidic bond-cleaving reaction of a 2-deoxy-2-acetamido glycoside [1]. Solution studies have shown that the 2-acetamido N-acetyl group enhances spontaneous hydrolysis, of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside relative to methyl α-D-glucopyranoside, by more than 1000-fold [2]. An oxazolinium ion can be deprotonated to give an oxazoline, which is a stable and isolable species. Oxazolinium ions are common intermediates in the neighboring group participation mechanism of glycoside hydrolases, including glycoside hydrolases from families GH18, GH20, GH25, GH56, GH84, and GH85.

Mechanism for conversion of a 2-acetamido-2-deoxy-β-D-glycoside to an oxazolinium ion and oxazoline.

Anchimeric assistance can occur with modified 2-acetamido groups, such as 2-glycolylamido groups, affording hydroxymethyl substituted oxazolinium ion intermediates, such as that demonstrated for the glycoside hydrolases of GH84 [3].

See also

• Oxocarbenium ion

References

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1. Tews, I., Terwisscha van Scheltinga, A.C., Perrakis, A., Wilson, K.S., and Dijkstra, B.W. J. Am. Chem. Soc. 1997, 119, 7954-7959.

2. Piszkiewicz, D.; Bruice, T. C. J. Am. Chem. Soc. 1968, 90, 5844-5848.