51667-66-4

A series of ring-substituted analogues of imidazole-4-acetic acid (IAA, 4), a partial agonist at both GABAA and GABAC receptors (GABA = γ-aminobutyric acid), have been synthesized. The synthesized compounds 8a-1 have been evaluated a

Bisphosphonates (BPs) are pyrophosphate analogues in which the oxygen in P-O-P has been replaced by a carbon, resulting in a metabolically stable P-C-P structure. Pamidronate (1b, Novartis), a second-generation BP, was the starting point for extensive SAR studies. Small changes of the structure of pamidronate lead to marked improvements of the inhibition of osteoclastic resorption potency. Alendronate (1c, MSD), with an extra methylene group in the N-alkyl chain, and olpadronate (1h, Gador), the N,N-dimethyl analogue, are about 10 times more potent than pamidronate. Extending one of the N-methyl groups of olpadronate to a pentyl substituent leads to ibandronate (1k, Roche, Boehringer-Mannheim), which is the most potent close analogue of pamidronate. Even slightly better antiresorptive potency is achieved with derivatives having a phenyl group linked via a short aliphatic tether of three to four atoms to nitrogen, the second substituent being preferentially a methyl group (e.g., 4g, 4j, 5d, or 5r). The most potent BPs are found in the series containing a heteroaromatic moiety (with at least one nitrogen atom), which is linked via a single methylene group to the geminal bisphosphonate unit. Zoledronic acid (6i), the most potent derivative, has an ED50 of 0.07 mg/kg in the TPTX in vivo assay after sc administration. It not only shows by far the highest therapeutic ratio when comparing resorption inhibition with undesired inhibition of bone mineralization but also exhibits superior renal tolerability. Zoledronic acid (6i) has thus been selected for clinical development under the registered trade name Zometa. The results of the clinical trials indicate that low doses are both efficacious and safe for the treatment of tumor-induced hypercalcemia, Paget's disease of bone, osteolytic metastases, and postmenopausal osteoporosis.

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A novel structural class of highly potent and selective 5-HT3 receptor antagonists is described.The compounds in this new series contain a thiazole moiety linking an aromatic group and a nitrogen-containing basic region; the thiazole group appears to be acting as a carbonyl bioisostere in this system.An optimized member of this series, 4-(2-methoxyphenyl)-2-methyl>thiazole (5), exhibits oral activity in the Bezold-Jarisch reflex paradigm comparable to or better than the standard agents ondansetron (1) and ICS-205-930 (2).Several of the structure-activity relationships are rationalized in terms of a computer pharmacophore model for 5-HT3 receptor binding.

4-(2-Methoxyphenyl)-2-[4(5)-methyl-5(4)-imidazolylmethyl]thiazole (5) is a highly potent member of a structurally novel series of selective serotonin-3 receptor antagonists. The synthesis of tritriated 5 and its binding profile in neuroblastoma-glioma 108

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