Optically active antifungal azoles: synthesis and antifungal activity of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-{2-[4-aryl-piperazin-1-yl]- ethyl}-tetrazol-2-yl/1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol q Ram Shankar Upadhayaya, a Neelima Sinha, a Sanjay Jain, a Nawal Kishore, a Ramesh Chandra b and Sudershan K. Arora a, * a Medicinal Chemistry Division, New Chemical Entity Research, Lupin Research Park, 46/47 A, At Village Nande, Taluka Mulshi, Pune 411042, India b Bundelkhand University, Jhansi, India Received 21 November 2003; accepted 10 February 2004 Abstract—A series of (2R,3S)-2-(2,4-difluorophenyl)-3-(5-{2-[4-aryl-piperazin-1-yl]-ethyl}-tetrazol-2-yl)-1-[1,2,4]-triazol-1-yl-butan- 2-ol (11a–n) and (2R,3S)-2-(2,4-difluorophenyl)-3-(5-{2-[4-aryl-piperazin-1-yl]-ethyl}-tetrazole-1-yl)-1-[1,2,4]-triazol-1-yl-butan-2-ol (12a–n) has been synthesized. The antifungal activity of compounds was evaluated by in vitro agar diffusion and broth dilution assay. Compounds 11d and its positional isomer 12d having 3-trifluoromethyl substitution on the phenyl ring of piperazine dem- onstrated significant antifungal activity against variety of fungal cultures (Candida spp. C. neoformans and Aspergillus spp.). The compound 12d showed MIC value of 0.12 lg/mL for C. albicans, C. albicans V-01-191A-261 (resistant strain); 0.25 lg/mL for C. tropicalis, C. parapsilosis ATCC 22019 and C. krusei and MIC value of 0.5 lg/mL for C. glabrata, C. krusei ATCC 6258, which is comparable to itraconazole and better than fluconazole. Further, compound 11d showed significant activity (MIC; 0.25–0.5 lg/mL) against Candida spp. and strong anticryptococcal activity (MIC; 0.25 lg/mL) against C. neoformans. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction The incidence of systemic fungal infections such as Candidosis, Cryptococcosis and Aspergillosis has been increasing recently due to an increase in the number of immunocompromised hosts. For the treatment of these infections, the new antifungal azoles have been devel- oped for clinical use. Attention has been paid to triazole derivatives because of their generally broad antifungal spectrum and low toxicity. 1 Triazole derivatives displace lanosterol from lanosterol 14-demethylase (14 DM), a cytochrome P-450-dependent enzyme, and block the biosynthesis of an essential component of fungal cell membrane, ergosterol. 2 Fluconazole has relatively low antifungal activity in vitro, but it is water soluble, and has excellent pharmacokinetic properties. 3;10 It is effec- tive against candidiasis after both oral administration and injection. However, its activity against Aspergillus seems limited. Itraconazole has an excellent and broader antifungal spectrum. 4 Newer triazole agents such as voriconazole, 5 posaconazole 6 and ravuconazole, 7 are active against Aspergillus and currently under clinical trials (Fig. 1). In order to seek new triazole antifungal agents we de- signed a series of tetrazole–triazole compounds depicted by the formula 11 and 12. We presumed that the left half portion of the molecule is essential to the high anti- fungal activity. It is a common substructure seen in many other triazole antifungals. The 1-aryl-4-(2-[1H- tetrazol-5-yl]-ethyl)-piperazine ring was introduced in the expectation that: (1) since salt of aryl piperazine moieties will make molecule more water soluble than simple hydrocarbon moieties, the compound could be more easily delivered to the target enzyme; (2) since many other triazole antifungal agents have heteroatoms at the corresponding part of the molecule, complemen- tary structure of the target enzyme would be implied; and (3) a variety of aryl piperazines should be available Keywords: Antifungal activity; Tetrazole derivatives; Chiral synthesis; Tetrazole–triazole compounds. q Taken in part from the PhD dissertation of Ram Shankar Up- adhayaya, Bundelkhend University, 2003. * Corresponding author. Tel.: +91-20-25126689; fax: +91-20-25126175; e-mail addresses: sudershanarora@hotmail.com, sudershanarora@ lupinpharma.com 0968-0896/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmc.2004.02.014 Bioorganic & Medicinal Chemistry 12 (2004) 2225–2238