Research Article Design and Synthesis of Novel Isoxazole Tethered Quinone-Amino Acid Hybrids P. Ravi Kumar, 1,2 Manoranjan Behera, 1 M. Sambaiah, 1 Venu Kandula, 1 Nagaraju Payili, 1 A. Jaya Shree, 2 and Satyanarayana Yennam 1 1 Department of Medicinal Chemistry, GVK Biosciences Pvt. Ltd., Plot No. 28, IDA, Nacharam, Hyderabad, Andhra Pradesh 500 076, India 2 Centre for Chemical Sciences & Technology, Institute of Science and Technology, Jawaharlal Nehru Technological University, Kukatpally, Hyderabad, Andhra Pradesh 500 072, India Correspondence should be addressed to Manoranjan Behera; manoranjan.behera@gvkbio.com Received 26 June 2014; Accepted 14 October 2014; Published 19 November 2014 Academic Editor: Sambasivarao Kotha Copyright © 2014 P. Ravi Kumar 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. A new series of isoxazole tethered quinone-amino acid hybrids has been designed and synthesized involving 1,3-dipolar cycloaddition reaction followed by an oxidation reaction using cerium ammonium nitrate (CAN). Using this method, for the frst time various isoxazole tethered quinone-phenyl alanine and quinone-alanine hybrids were synthesized from simple commercially available 4-bromobenzyl bromide, propargyl bromide, and 2,5-dimethoxybenzaldehyde in good yield. 1. Introduction Compounds containing the quinone group present an impor- tant class of biologically active molecules that are widespread in nature [1–3]. Te discoveries of antibiotic [4, 5] and antitumor [6] properties assigned to several natural quinones have raised interest among scientists for use as pharmaceu- ticals. While antibiotics display an enormous diversity in chemical structures, quinone antibiotics such as Adriamycin, Mitomycin C, and Streptonigrin deserve special attention [7–10]. In this context, search of new molecules containing quinone moiety has always fascinated the organic as well as medicinal chemist. Isoxazole derivatives are an important class of het- erocyclic pharmaceuticals and bioactive natural products because of their signifcant and wide spectrum of biological activities, including potent and selective antagonism of the NMDA receptor and anti-HIV activity . [11, 12]. It shows anti- hyperglycemic [13], analgesic [14], anti-infammatory [15], antifungal [16], and antibacterial activity [17]. 3,5-Disubsti- tuted isoxazole derivatives which are biological active include muscimol, dihydromuscimol, micafungin, and cycloserine [18, 19]. Unnatural amino acids, the nonproteinogenic - amino acids that occur either naturally or chemically synthe- sized, have been used widely as chiral building block. Tey have been also used as molecular scafolds in constructing combinatorial libraries [20]. Tey represent a powerful tool in drug discovery when incorporated into therapeutic pep- tidomimetics and peptide analogs [21]. Te seminal work on the synthesis of unnatural amino acids has been done by O’Donnell and Maruoka independently, which accelerated the application of this class of amino acid for practical applications [22, 23]. Synthesis of hybrid natural products has gained momen- tum in recent years [24–26]. It is expected that combin- ing features of more than one biologically active natural segment in a single molecule may result in pronounced pharmacological activity while retaining high diversity and biological relevance. Tere are a few reports describing the preparation of quinone-hybrid with other natural products. For example, quinone-amino acids [27], sugar-oxasteroid- quinone [28], quinone-annonaceous acetogenins [29], and conduritol-carba-sugar [30] hybrids have been described using diferent synthetic protocol. Hindawi Publishing Corporation Journal of Amino Acids Volume 2014, Article ID 721291, 14 pages http://dx.doi.org/10.1155/2014/721291