Synthesis and Crystal Structure Determination of Cyclosporin H

Abstract
Acid-catalyzed degradation of cyclosporin A was studied in various solvents and products of reaction were monitored by HPLC. Identification of amino acids and their chirality were determined after hydrolysis and derivatization by GC-MS. Cyclosporin H was isolated as the principal product and its structure was determined by X-ray diffraction: Cyclosporin H- diethyl ether-water (1 : 0.5 : 1) crystallizes in the monoclinic space groupI2witha= 12.338(2) Å,b= 18.963(2) Å,c= 34.074(3) Å, β = 96.47(2)°,Z= 4, andV= 7 921.4(17) Å3.