1. For Part 19 see: Reisch J., Usifoh C. O., Okoh E., Oluwadiya J. O. Pharmazie (in press)
2. A part of the Ph.D. thesis of C. O. Usifoh, University of M�nster (in preparation)
3. Monge A., Martinez-Merino V., Sammartin C., Ochoa M. C., Fernandez-Alvarez E. (1990) Arzneim.-Forsch.40: 1349
4. Grivsky E. M., Lee S., Sigel C. W., Duch D. S., Nichol C. A. (1980) J. Med. Chem.23: 327
5. Robins R. K., Hitchings G. H. (1955) J. Am. Chem. Soc.77: 2256