1. The Graduate School, University of Santo Tomas, España Blvd., Manila 1015, Philippines
2. Laboratory for Organic Reactivity, Discovery and Synthesis (Rm. 410), Research Center for the Natural and Applied Sciences, University of Santo Tomas, Espana Blvd., Manila 1015, Philippines
3. Chemistry Department, College of Science and Mathematics, Mindanao State University-Iligan Institute of Technology, Tibanga, Iligan City 9200, Philippines