Jordan, Stephan; Schwemler, Christoph; Kosch, Winfried; Kretschmer, Axel; Schwenner, Eckhardt; Stropp, Udo; Mielke, Burkhard Bioorganic and Medicinal Chemistry Letters, 1997, vol. 7, # 6 p. 681 - 686 doi: 10.1016/S0960-894X(97)00079-6