Cyclosporin C is an immunosuppressant that has revolutionized organ transplantation through its use in the prevention of graft rejection. A group of nonpolar cyclic oligopeptides with immunosupppressant activity.

The selective and reversible insertion of pseudo-proline (?Pro) systems in cyclosporin C (CsC) featuring different C(2) substituents at the oxazolidine ring and its impact on the conformational and biological properties is described. The presence of a 5-membered ring exerts drastic effects upon the backbone conformation of CsC as demonstrated by NMR analysis. For example, the number of conformations, in particular in DMSO-d6, is strongly reduced and a cis 1-2 amide bond is induced when dialkylated at the C(2) position, resulting in a complete loss of the binding capacity to its receptor CypA. The reversibility of ?Pro insertion allows the temporary introduction of conformational constraints representing a new strategy in pro-drug design.

"Cyclosporin C is the main antifungal compound produced by Acremonium luzulae."
By M Moussaif, P Jacques, P Schaarw?chter, H Budzikiewicz, and P Thonart. Centre Wallon de Biologie Industrielle, University of Liege, Belgium.

"Administration diluents differentiate Neoral from a generic cyclosporine oral solution"
Writen by Kovarik J.M; Barilla D; McMahon L.; Wang Y; Kisicki J; Schmouder R

"Pseudoprolines (YPro): Targeting Bioactive Conformations of Cyclosporine Analogues"
Writen by Luc Patiny, Michael Keller, Torsten W?hr, Jean-Fran?ois Guichou and Manfred Mutter. Institute of Organic Chemistry, University of Lausanne, BCH-Dorigny, CH-1015 Lausanne, Switzerland

"Cyclosporin C(2) and C(0) concentration monitoring in stable, long-term heart transplant recipients receiving metabolic inhibitors."
Writen by Ray JE, Keogh AM, McLachlan AJ, Akhlaghi F. Department of Clinical Pharmacology and Toxicology, Institute of Laboratory Medicine, Sydney, Australia