Issue 5, 2013

Synthesis and stereochemical analysis of β-nitromethane substituted γ-amino acids and peptides

Abstract

The high diastereoselectivity in the Michael addition of nitromethane to α,β-unsaturated γ-amino esters, crystal conformations of β-nitromethane substituted γ-amino acids and peptides are studied. Results suggest that the N-Boc protected amide NH, conformations of α,β-unsaturated γ-amino esters and alkyl side chains play a crucial role in dictating the high diastereoselectivity of nitromethane addition to E-vinylogous amino esters. Investigation of the crystal conformations of both α,β-unsaturated γ-amino esters and the Michael addition products suggests that an H–Cγ–Cβ[double bond, length as m-dash]Cα eclipsed conformer of the unsaturated amino ester leads to the major (anti) product compared to that of an N–Cγ–Cβ[double bond, length as m-dash]Cα eclipsed conformer. The major diastereomers were separated and subjected to the peptide synthesis. The single crystal analysis of the dipeptide containing β-nitromethane substituted γ-amino acids reveals a helical type of folded conformation with an isolated H-bond involving a nine-atom pseudocycle.

Graphical abstract: Synthesis and stereochemical analysis of β-nitromethane substituted γ-amino acids and peptides

Supplementary files

Article information

Article type
Paper
Submitted
24 Oct 2012
Accepted
23 Nov 2012
First published
26 Nov 2012

Org. Biomol. Chem., 2013,11, 803-813

Synthesis and stereochemical analysis of β-nitromethane substituted γ-amino acids and peptides

M. Ganesh Kumar, S. M. Mali and H. N. Gopi, Org. Biomol. Chem., 2013, 11, 803 DOI: 10.1039/C2OB27070F

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