The studies on the chemical constituents of Taraxacum wallichii and Salvia cabulica were carried out at the H.E.J. Research Institute of Chemistry, University of Karachi, under the supervision of Prof. Dr. Viqar Uddin Ahmad. The phytochemical investigations on T. wallichii and S. cabulica resulted in the isolation and characterization of a new guaianolide taraxacin, and six known compounds. The work on the synthesis of the analogues of Jasplakinolide a 19-membered macrocycle having potent insecticidal, antifungal and cytotoxic activity was done at the Institüt Für Organische Chemie, Eberhard Karls Universität Tüebingen, Germany, under the supervision of Prof. Dr. Martin E. Maier. The research was funded by DAAD (German Academic Exchange Service) from 01.10.2001 to 30.09.2003. This project also involved synthesis of analogues of beta amino acids. These analogues of jasplakinolide were compared with natural product to study the effect of structural variation on the biological activity.