Synthesis of a new class of 2,3-dihydro-2-oxo-1H-benzimidazole-1-carboxylic acid derivatives as highly potent 5-HT3 receptor antagonists.
A series of 2,3-dihydro-2-oxo-1H-benzimidazole-1-carboxylic acid esters and amides containing a basic azacyclo- or azabicycloalkyl moiety has been synthesized and evaluated for 5-HT3 antagonistic activity in a radioligand binding assay ([3H]ICS 205930) and in the 5-HT-induced von Bezold-Jarisch reflex in the rat. It was found that endo-substituted azabicycloalkyl derivatives (e.g. 7a, 12a, 12b) were much more active than the corresponding exo analogues (e.g. 7b, 12h, 12i) or azacycloalkyl compounds. Amidic derivatives 12a, 12b, 12c, 12e, 13b, and 13c proved to be about 10 times more active than the corresponding ester derivatives 7a, 11a, 7c, 7d, 8a, and 8b. In particular, compound 12a (DA 6215) showed a Ki = 3.8 nM in the binding test and an ED50 = 1 nM/kg iv in the von Bezold-Jarisch reflex assay, an activity comparable to that of the reference compound 2 (ICS 205930, Ki = 2 nM, ED50 = 2.1 nM/kg). IR spectroscopy studies in the solid state and in CHCl3 solution revealed the existence of an intramolecular hydrogen bond in 13b, taken as a model compound for this class of substances. A molecular modeling study showed that 12a, in its internal hydrogen-bound conformation, well matches a recently proposed pharmacophoric model for 5-HT3 antagonist activity.
Turconi
M
M
Department of Medicinal Chemistry, Istituto De Angeli, Milan, Italy.
Nicola
M
M
Quintero
M G
MG
Maiocchi
L
L
Micheletti
R
R
Giraldo
E
E
Donetti
A
A
D000818:Animals; D001562:Benzimidazoles / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D001667:Binding, Competitive; D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D001952:Bridged-Ring Compounds / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D003198:Computer Simulation; D006860:Hydrogen Bonding; D007211:Indoles / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D011869:Radioligand Assay; D051381:Rats; D011985:Receptors, Serotonin / Q000378:metabolism; D012018:Reflex / Q000187:drug effects; D012702:Serotonin Antagonists / Q000138:chemical synthesis / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D000077526:Tropisetron
D001562:Benzimidazoles; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D001952:Bridged-Ring Compounds; D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C070191:itasetron; D000077526:Tropisetron