CONFORMATION OF CYCLIC HEPTAPEPTIDES - SOLID AND SOLUTION-STATE CONFORMATION OF YUNNANIN-A

The solid and solution state conformation of yunnanin A, a cyclic hept apeptide, cyclo(-Gly-Tyr-Gly-Gly-Pro-Phe-Pro-),: isolated from the roo ts of Stellaria yunnanensis were studied. The X-ray diffraction studie s showed that the crystal of yunnanin A [orthorhombic form from a etha nol-methanol mixture, a=11.754 (to), b=12.576 (7), c=30.731 (6) Angstr om, space group P222(1), z=4] had three intramolecular hydrogen bonds forming one type II, one type II' beta-turns, and a classical beta-bul ge unit with all trans amide bonds. The dominant solution conformation analyzed by NMR spectroscopy, Monte Carlo (MC) and restrained molecul ar dynamics (MD) calculations implemented in MacroModel/Batchmin (Ver. 4.5) was homologous to that in the solid state. (C) 1997, Elsevier Sc ience Ltd.