1. Department of Chemistry; Faculty of Science; Chulalongkorn University; Organic Synthesis Research Unit; Phayathai Road, Patumwan Bangkok 10330 Thailand
2. Department of Chemistry; Faculty of Science; Chulalongkorn University; Phayathai Road, Patumwan Bangkok 10330 Thailand
3. Division of Chemistry and Biological Chemistry; School of Physical and Mathematical Sciences; Nanyang Technological University; 21 Nanyang Link Singapore 637371 Singapore