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Molecules 2013, 18(12), 14739-14746; doi:10.3390/molecules181214739
Article

Examination of the Potential for Adaptive Chirality of the Nitrogen Chiral Center in Aza-Aspartame

 and *
Département de chimie, Université de Montréal, 2900 Boul. Edouard-Monpetit, Montréal, QC H3T 1J4, Canada
* Author to whom correspondence should be addressed.
Received: 3 October 2013 / Revised: 7 November 2013 / Accepted: 12 November 2013 / Published: 28 November 2013
(This article belongs to the Special Issue Dynamic Stereochemistry)
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Abstract

The potential for dynamic chirality of an azapeptide nitrogen was examined by substitution of nitrogen for the α-carbon of the aspartate residue in the sweetener S,S-aspartame. Considering that S,S- and R,S-aspartame possess sweet and bitter tastes, respectively, a bitter-sweet taste of aza-aspartame 9 could be indicative of a low isomerization barrier for nitrogen chirality inter-conversion. Aza-aspartame 9 was synthesized by a combination of hydrazine and peptide chemistry. Crystallization of 9 indicated a R,S-configuration in the solid state; however, the aza-residue chiral center was considerably flattened relative to its natural amino acid counterpart. On tasting, the authors considered aza-aspartame 9 to be slightly bitter or tasteless. The lack of bitter sweet taste of aza-aspartame 9 may be due to flattening from sp2 hybridization in the urea as well as a high barrier for sp3 nitrogen inter-conversion, both of which may interfere with recognition by taste receptors.
Keywords: azapeptide; peptide mimic; aspartame; dynamic chirality; hydrazine; taste; crystal structure; nitrogen chirality; semicarbazide azapeptide; peptide mimic; aspartame; dynamic chirality; hydrazine; taste; crystal structure; nitrogen chirality; semicarbazide
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Bouayad-Gervais, S.H.; Lubell, W.D. Examination of the Potential for Adaptive Chirality of the Nitrogen Chiral Center in Aza-Aspartame. Molecules 2013, 18, 14739-14746.

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