Synthesis and conformational analysis of cyclo-TRI[l-valyl-d-hexahydromandelyl] |
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Authors: | Murray Goodman Alvin Steinfeld Alan Tonelli Ugo Lepore Manlio Palumbo Bernard Donzel |
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Affiliation: | Department of Chemistry, University of California San Diego, La Jolla, California 92037 USA |
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Abstract: | The synthesis of the cyclo-hexadepsipeptide [l-valyl-d-hexahydromandelyl]3 is described. Examination of this macrocyclic compound by 220-MHz nuclear magnetic resonance spectroscopy shows that symmetrical conformations are stabilized in strongly polar solvents (trifluoroacetic acid, acetonitrile), whereas asymmetric conformations are preferred in nonpolar or slightly polar media such as carbon tetrachloride, chloroform, cyclohexane, and benzene.From analysis of the temperature dependence of the chemical shift and of the coupling constants, together with conformational energy calculations, a model is proposed for the preferred conformation of this molecule in nonpolar solvents. |
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