1. Department of Pharmaceutical Chemistry, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji 192-0392, Tokyo, Japan
2. Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 8 Street Kliment Ohridski Blvd., Sofia 1756, Bulgaria
3. Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Avenue, Bldg. 9, Sofia 1113, Bulgaria