Axially Chiral 1,7-Naphthyridine-6-carboxamide Derivatives as Orally Active Tachykinin NK1 Receptor Antagonists: Synthesis, Antagonistic Activity, and Effects on Bladder Functions
- 1 September 1999
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of Medicinal Chemistry
- Vol. 42 (19) , 3982-3993
- https://doi.org/10.1021/jm990220r
Abstract
Cyclic analogues of N-[3,5-bis(trifluoromethyl)benzyl]-7,8-dihydro-N,7-dimethyl-5-(4-methylphenyl)-8-oxo-1,7-naphthyridine-6-carboxamide (1) having a 6−9-membered ring (6−9) were synthesized and evaluated for NK1 antagonistic activities. The 8-membered ring compound with a β-methyl group at the C(9)-position, (aR,9R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10,11-tetrahydro-9-methyl-5-(4-methylphenyl)-7H-[1,4]diazocino[2,1-g][1,7]naphthyridine-6,13-dione [(aR,9R)-8b], was atropodiastereoselectively synthesized by cyclization of a chiral intermediate, 10 g. On the other hand, the 7-membered ring compound with a β-methyl group at the C(9)-position [(9S)-7b] was obtained as an equilibrium mixture of atropisomers with a ratio of ca. 3:2 in solution at room temperature (measured by NMR in CDCl3). Compounds (9S)-7b and (aR,9R)-8b exhibited excellent antagonistic activities both in vitro [IC50 (inhibition of [125I]BH-SP binding in human IM-9 cells) = 0.28 and 0.45 nM, respectively] and in vivo (iv and po). Significantly, the in vitro activity of (aR,9R)-8b was ca. 750-fold higher than that of its enantiomer (aS,9S)-8b, ca. 40-fold higher than its atropisomer (aS,9R)-8b, and ca. 20-fold higher than its diastereomer (aR,9S)-8b. The structure−activity relationships in this series, along with the X-ray analysis of (aR,9R)-8b, indicated that the stereochemistry around the −C(6)(O)−N(7)−CH2Ar moiety is important for NK1 receptor recognition. The NK1 antagonists showed effects on bladder functions in guinea pigs upon intravenous injection: i.e., the antagonists increased the shutdown time of distension-induced rhythmic bladder contractions and the bladder volume threshold, and the effects on the shutdown time were found to correlate well with the NK1 antagonistic activities. Compound (aR,9R)-8b has been identified as a potential clinical candidate for the treatment of bladder function disorders.Keywords
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