S-32 Symposium on the Future Prospect of Natural Products in Pharmaceutical Sciences -Isolation, Synthesis, and Biological Activity-   S32-1. Development of Novel Opioid Ligands Based on the Rubiaceous Indole Alkaloids   S32-2. Isolation and Structure-Activity Relationships of Antitumor Substances from Higher Plants   S32-3. Chemistry and Biology of Neurotrophic Natural Products   S32-4. Syntheses of Neuroprotective Bridged Diterpenes   S32-5. Synthetic Studies on Securinega Alkaloids