Phytochemical investigations on the medicinal plants of Turkish and Pakistani origin have resulted in the isolation of several new natural products. Buxus sempervirens and Fritillaria persica of Turkish origin have yieled several new steroidal alkaloids. New withanolides and furanoid diterpenoids were isolated from Withania somnifera and Tinospora malabarica of Pakistani origin. Chemical transformations of catharanthine and leurosine into vinblastine and its analogues was also achieved. The CD in situ complexation method has been developed as a tool for the determination of absolute configurations of Cottonogenic derivatives. © 1994 IUPAC