1. Department of Organic Chemistry, Technical University of Budapest, H-1521 Budapest, Hungary, Research Group for Alkaloid Chemistry, Hungarian Academy of Sciences, H-1521 Budapest, Hungary, Department of Organic Chemistry, Eötvös Lorand University, H-1518 Budapest, Hungary, Department of Chemistry, Southern Utah University, Cedar City, Utah 84720, and Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602