Synthesis and antiemetic activity of 1,2,3,9-tetrahydro-9-methyl-3-(4-substituted-piperazin-1-ylmethyl)-4 H -carbazol-4-one derivatives

Frontiers of Chemistry in China 01/2009; 4(1):63-68. DOI: 10.1007/s11458-009-0017-8

ABSTRACT 5-HT3 receptor antagonists, such as Ondansetron, are used for anti-emesis after chemotherapy, radiotherapy and operations. Some
Ondansetron analogs possessing piperazine ring as side chains were synthesized in our lab. Thus, one of the two carbonyl groups
of starting material 1,3-cyclohexandione (1) was condensed with phenylhydrazine hydrochloride to form monophenylhydrazone (2). 1,2,3,9-Tetrahydro-4H-carbazol-4-one (3) was prepared from 2
via cyclization and rearranged in the presence of ZnCl2. Through a methylation reaction, compound 3 was converted to 1,2,3,9-tetrahydro-9-methyl-4H-carbazol-4-one (4). 3-Dimethylaminomethyl substituted compound (5) was synthesized from 4 by a Mannich reaction in glacial acetic acid. Nine novel 1,2,3,9-tetrahydro-9-methyl-3-(4-substituted-piperazin-1-ylmethyl)-4H-carbazol-4-one derivatives (6a–6i) were synthesized through nucleophilic substitution reaction of 5 with piperazines. The structures of all the target compounds were determined by elemental analysis, IR, MS, 1H NMR and 13C NMR spectra. The results of preliminary pharmacological test show that part of the novel compounds have antiemetic activity
comparable to that of the control Ondansetron.

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