1. School of
Chemical Sciences, Universiti Sains Malaysia, 11800 USM, P. Pinang, Malaysia
2. Department of Chemistry, Faculty
of Science, University of Malaya, 50603
Kuala Lumpur, Malaysia
3. Centre
de Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS,
1, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France