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Issue 13, 2008
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Synthetic and structural studies on macrocyclic amino cyclitols – conformational chameleons

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Abstract

Starting from quinic acid 7 the synthesis of 1,4-butanediol-linked macrocyclic aminocyclitols 30, 32, 34, 36 and 38 is described. Assembly was achieved by olefin cross-metathesis of appropriate cyclohexyl allyl ethers followed by ring-closing metathesis of bis-O-allyl homodimers. In all five cases studied, the only products that were formed were those resulting from direct ring-closing metathesis; the formation of larger rings was not detected. These macrocycles exhibited diverse conformational behaviour which included formation of stable separable conformers 31a and 31b as well as conformationally dynamic macrocycles 35 in which a ring flip in one cyclohexane chair conformer induces a ring flip of the other cyclohexane ring through the linking chains of the macrocycles. The activation energy for the inversion of the chair conformation in this process was determined to be about 38 kJ mol−1, which is about 7 kJ mol−1 lower than the activation energy for the ring flip of the unsubstituted cyclohexane ring. In all cases, the conformational studies strongly suggest that intramolecular H-bonding between 1,3-diaxially oriented amido and alcohol or ether groups exerts a decisive contribution to the overall stabilisation of the preferred cyclohexane chair conformation.

Graphical abstract: Synthetic and structural studies on macrocyclic amino cyclitols – conformational chameleons

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Publication details

The article was received on 23 Oct 2007, accepted on 07 Apr 2008 and first published on 07 May 2008


Article type: Paper
DOI: 10.1039/B716347A
Citation: Org. Biomol. Chem., 2008,6, 2412-2425
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    Synthetic and structural studies on macrocyclic amino cyclitols – conformational chameleons

    B. Oelze, D. Albert and A. Kirschning, Org. Biomol. Chem., 2008, 6, 2412
    DOI: 10.1039/B716347A

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