| Popis: |
The conformational behaviour of the peptide antibiotic leucinostatin A has been studied in solvents of different polarity using circular dichroism (CD) and infrared (i.r.) absorption. I.r. studies provided evidence of an intramolecularly hydrogen-bonded structure in CDC3 while CD studies suggested a helical conformation in leucinostatin A in lipophilic solvents. The tetrapeptide Boc-Aib-Leu-Leu-Aib-OMe, a fragment of leucinostatin A, was also studied both in solution and in solid state using X-ray diffraction. The crystal structure shows that the peptide backbone folds into a right-handed 310-helical conformation stabilized by two intramolecular 4 1 hydrogen bonds. The spectroscopic analysis in solution is consistent with the conformation found in solid state. Crystal data: orthorhombic, P212121, a= 23.583, b= 15.791, c= 9.554 A Z = 4; the final R and Rw are 0.090 and 0.126, respectively. |
