1. Department of Chemistry, Allama Iqbal Open University, Islamabad, Pakistan
2. Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan
3. Department of Chemistry, F C College University, Lahore, Pakistan
4. Division of Bioorganic Chemistry, School of Pharmacy, Saarland University, Campus B 2.1., D-66123 Saarbruecken, Germany