3MB-PP1 Compounds and possessed relatively low clogP
Compounds 11–13 and 15 possessed relatively low clogP values and tended to show relatively weak antagonist activity regardless of their potent EP1 receptor affinity. Compounds 2–4, which were selected based on their potent in vivo antagonist activity, were found to be effective in an animal model.
Biological assay method
Introduction Coleman et al. proposed the existence of specific receptors for thromboxane (TX), prostaglandin I (PGI), PGE, PGF, and PGD, which were named TP, IP, EP, FP, and DP, respectively. They further classified EP receptors into four subtypes, EP1–4, each of which responds to PGE2 in different way. A number of specific ligands for these receptors have been reported in the literature.2, 3, 4, 5 In our previous papers,6, 7, 8 we described the discovery of a highly selective EP1 receptor antagonist 1. As shown in Table 1, 1 showed a significant in vivo antagonist activity with respect to the sulprostone-induced increase of intravesical pressure of bladder in rats, whereas the corresponding tetrazole analog 2 showed increased activity as an EP1 antagonist in vivo in the same assay system. Analogs 1 and 2 were further evaluated for their ability to inhibit hepatic cytochrome P450 isozymes 1A2, 2C9, 2C19, 2D6, and 3A4, which are hepatic enzymes for drug metabolism. As shown in Table 2, the tetrazole analog, compound 2, strongly inhibited 2C9, 2C19, and 3A4 at a concentration of 3μM, whereas the corresponding carboxylic 3MB-PP1 analog 1 did not. Cytochrome P450 enzyme inhibition by drug candidates has been widely studied because of the potential for harmful drug interactions. For this reason, further optimization of acid analog 1, which has less potent inhibitory activity against all the P450 isozymes, was carried out for identifying drug candidates. We here report on the discovery of highly selective EP1 receptor antagonists without inhibitory activity against cytochrome P450 isozymes at realistic concentrations.
Chemistry Synthesis of test compounds is outlined in Schemes Scheme 1, Scheme 2, Scheme 3, Scheme 4. Compounds 3–5 were synthesized as described in Scheme 1. Palladium-catalyzed carbonylation of triflates derived from phenols 19a and b in the presence of methanol afforded methyl esters 20a and b. Bromination of 20a and b with N-bromosuccinimide in the presence of benzoyl perbromide provided 21a and b, respectively. Lithium aluminum hydride (LAH) reduction of 4-bromo-2-methyl benzoic acid 22 gave an alcohol 23. Palladium-catalyzed carbonylation of 23 in the presence of methanol provided a methyl benzoate 24, bromination of which afforded a benzylbromide 21c. Alkylation of a phenol intermediate 25 with benzyl halides 21a–c in the presence of potassium carbonate afforded 26a–c, respectively. Alkaline hydrolysis of methyl esters 26a–c gave 3–5, respectively. Synthesis of 6 is described in Scheme 2. Esterification of the benzoic acid 27 with diazomethane followed by LAH reduction gave a benzyl alcohol 28, protection of which as a MOM ether afforded 29. Trifluoromethanesulfonylation of 29 followed by palladium-catalyzed carbonylation in the presence of methanol provided 30, LAH reduction of which afforded a benzyl alcohol 31. O-Alkylation of the phenol residue of 25 using the Mitsunobu reaction gave 32, acidic deprotection of which gave 33. Oxidation of 33 with pyridinium-sulfur trioxide and then further oxidation with sodium hypochlorite afforded a carboxylic acid 6. Synthesis of 7–10, 12,–13 and 15–18 is described in Scheme 3a. O-Alkylation of nitrophenols 34a–d with appropriate halides afforded benzyl phenyl ethers 35a–f, respectively. Reduction of the nitro residue of 35a–f produced their corresponding anilines 36a–f, N-sulfonylation of which with appropriate sulfonyl chloride gave sulfonamides 37a–j, respectively. N-Alkylation of sulfonamides 37a–j with isobutyl iodide afforded 38a–j, respectively. Alkaline hydrolysis of 38a–j produced 7–10, 12–13, and 15–18, respectively.