1. Loker Hydrocarbon Research Institute and Department of Chemistry University of Southern California University Park Los Angeles CA 90089-1661 USA
2. Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo nam. 2 160 00 Prague 6 Czech Republic
3. Department of Organic Chemistry Faculty of Science Charles University Hlavova 2030/8 128 43 Prague Czech Republic
4. Department Chemistry The University of Alabama Tuscaloosa AL 35487 USA