CONFORMATIONAL STUDIES OF CYCLIC TETRAPEPTIDES - EVIDENCE FOR A BIS GAMMA-TURN CONFORMATION FOR CHLAMYDOCIN AND ALA4-CHLAMYDOCIN IN NON-POLAR SOLVENTS
- 1 January 1983
- journal article
- research article
- Vol. 21 (1) , 35-42
Abstract
The conformations of chlamydocin [cytotoxic agent from Diheterospora chlamydospora] and cyclo (Ala-Aib-Phe-D-Pro)(Ala4-chlamydocin) in chloroform were investigated by NMR, IR and circular dichroism spectroscopy. The data obtained from these experiments establish an all transoid, bis .gamma.-turn conformation for both compounds in chloroform with the following torsional angles (.+-.20.degree.): Ala4-chlamydocin: Aib [.alpha.-aminoisobutyric acid], .vphi. +60.degree., .psi. -50.degree.; .omega. +160.degree.; Phe .vphi. -120.degree., .psi. +120.degree., .omega. -160.degree.; D-Pro .vphi. +60.degree., .psi. -55.degree., .omega. +160.degree.; Ala .vphi. -110.degree., .psi. +110.degree., .omega. -160.degree.. Chlamydocin adopts a closely related conformation in neat chloroform. Nuclear Overhauser Effect (NOE) data are utilized to assign amide bond geometries in the cyclic tetrapeptide ring system.This publication has 6 references indexed in Scilit:
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