* Corresponding authors

^a Department of Chemistry, University of Southern California, Los Angeles, USA
E-mail: mckenna@usc.edu
Fax: +1 213 740 0930
Tel: +1 213 740 2698

^b Institute of Organic Chemistry, Technical University of Lodz, Zeromskiego St. 116, 90-924 Lodz, Poland
E-mail: kblazew@p.lodz.pl
Fax: +48 42 636 55 30
Tel: +48 42 631 31 46

^c Procter & Gamble Pharmaceuticals, Mason, USA
Tel: +1 513 622 3630

^d Warner Chilcott, Dundalk, Louth, Ireland
E-mail: frank.ebetino@wcrx.com