Research Article Microwave-Assisted Synthesis and Antimicrobial Activity of Some Novel Isatin Schiff Bases Linked to Nicotinic Acid via Certain Amino Acid Bridge Ahmed M. Naglah, 1,2 Hassan M. Awad, 3 Mashooq A. Bhat, 4 Mohamed A. Al-Omar, 1 and Abd El-Galil E. Amr 1,5 1 Department of Pharmaceutical Chemistry, Drug Exploration & Development Chair, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia 2 Peptide Chemistry Department, Chemical Industries Research Division, National Research Centre, Dokki, Cairo 12622, Egypt 3 Chemistry of Natural and Microbial Products Department, Pharmaceutical Industries Division, National Research Centre, Dokki, Cairo 12622, Egypt 4 Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia 5 Applied Organic Chemistry Department, National Research Centre, Dokki, Cairo 12622, Egypt Correspondence should be addressed to Ahmed M. Naglah; amnaglah@gmail.com Received 1 October 2014; Revised 30 November 2014; Accepted 21 December 2014 Academic Editor: Rabah Boukherroub Copyright © 2015 Ahmed M. Naglah et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te coupling reaction of nicotinic acid with certain L-amino acid methyl esters including valine, leucine, and phenylalanine was done by the use of acid chloride method. Te products were reacted with hydrazine hydrate 99% to give the corresponding hydrazides that were reacted with indoline-2,3-dione (isatin) to get Schif bases under the application of microwave irradiation technique. Tese novel compounds were characterized by means of their FT-IR, 1 H NMR, and mass spectral data. Additionally, the specifc optical rotation and elemental analysis were measured. Te in vitro antimicrobial activity of the synthesized compounds was evaluated by agar difusion method. Te compounds showed a strong antimicrobial inhibitory activity. Most of the test compounds possessed a broad spectrum of activities having MIC values ranging from 50 g/mL to 500 g/mL. 1. Introduction Nicotinic acid (pyridine-3-carboxylic acid), also known as niacin and vitamin B3, is found in various plants and animals; also, it has vital roles in such biological processes as production of energy [1]. Nicotinic acid derivatives and its isomers have antibacterial, antioxidant, anti-infammatory, anticarcinogenic, and antitubercular activities [2], signal transduction, regulation of gene expression [3], and involve- ment in the synthetic pathway of lipids [4]. On the other hand, some of new heterocyclic and peptide derivatives have been studied with respect to antivirus [5], anti-infammatory [6], enzymatic peptide [7], and antimicrobial activities [8, 9]. Also, there are several successful publications of microwave- assisted solid phase peptide synthesis of various unnatural biopolymers such as peptoids, pseudopeptides, small pep- tides [10], phosphopeptides [11], difcult peptides [12], - peptide libraries [13], and glycopeptides [14]. It is as well known that isatin is an endogenous compound identifed in humans and that its biological properties include a range of actions in the brain; it ofers protection against certain types of infections [15]. Isatin constitutes an important class of bioactive compounds exhibiting caspase inhibitor [16, 17], antiproliferative [18], and antibacterial activities [19]. Furthermore, novel inhibitors of mycobacterium tubercu- losis, prepared from indoline-2,3-dione (isatin) derivatives by the use of microwave irradiation technique, have been reported [20]. Due to the importance of nicotinic acid derivatives, amino acids, peptides, and isatin as bioactive compounds and Hindawi Publishing Corporation Journal of Chemistry Volume 2015, Article ID 364841, 8 pages http://dx.doi.org/10.1155/2015/364841