1. Department of Organic Chemistry, University of Debrecen, P.O. Box 20, H‐4010 Debrecen, Hungary;
2. Department of Biochemistry, University of Debrecen, 1 Egyetem tér, H‐4032 Debrecen, Hungary
3. Department of Pharmaceutical Chemistry, University of Debrecen, P.O. Box 70, H‐4010 Debrecen, Hungary
4. Department of Chemistry, Laboratory for X‐ray Diffraction, University of Debrecen, P.O. Box 7, H‐4010 Debrecen, Hungary