5,5’-Biindole

Abstract: Synthesis of 5,5’-biindole was carried out by the Madelung indole reaction. Understrong basic conditions and high temperatures (350 oC), $,’ - bis -formyl- o -tolidineunderwent cyclization to produce high amounts of the dimeric indole. Full and unambiguousassignments of all 1 H- and 13 C-NMR resonances of indole and 5,5’-biindole in DMSO- d 6 arealso reported. Keywords: Indoloquinolizine, Antitumor activity, Teuber’s reaction, Indole synthesis, 1 H-NMR, 13 C-NMR. Introduction Indoles are one of the most widely distributed heterocyclic compounds in nature [1-3]. The indole ringappears in tryptophan [4], an essential aminoacid, and metabolites of tryptophan are important in thebiological chemistry of both plants and animals. In plants, indole alkaloids, including indole-3-acetic acidand its secondary metabolites, are known as plant growth hormones [5]; in animals, serotonin(5-hydroxytryptamine) is a crucial neurotransmitter in the central nervous system [6]. The potentphysiological properties of these indole derivatives led to vast research of their use as medicines in thefield of pharmaceutical chemistry. Furthermore, indomethacin [7], a non-steroidal anti-inflammatoryagent, and pindolol [8], a b-adrenergic blocker, are clinically proven indole compounds. Several naturally-occurring indoles are also of clinical relevance; vincristine, a dimeric indole alkaloid, and relatedcompounds, were the first of the antimitotic class of chemotherapeutic agents for cancer [9]. Themitomycins [10] and derivatives of ellipticine [11] are other examples of compounds having antitumoractivity. Extensive research on reactivity and synthesis of indoles has been done and there is increased