1. Department of Chemical Informatics, Faculty of Education, University of Szeged, Boldogasszony sgt. 6, 6725 Szeged, Hungary, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo náméstí 2, 16610 Prague 6, Czech Republic, and Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6