1. a Bristol-Myers Squibb Pharmaceutical Research Institute , P.O. Box 191, New Brunswick , NJ , 08903 , USA
2. b Bell Communications Research , 331 Newman Springs Road, Red Bank , NJ , 07701 , USA
3. c Laboratory of Organic Chemistry , Delft University of Technology , Julianalaan 136, 2628 BL , Delft , The Netherlands