Pravadoline (1) is an (aminoalkyl)indole analgesic agent which is an inhibitor of cyclooxygenase and, in contrast to other NSAIDs, inhibits neuronally stimulated contractions in mouse vas deferens (MVD) preparations (IC50 = 0.45 microM). A number of conformationally restrained heterocyclic analogues of pravadoline were synthesized in which the morpholinoethyl side chain was tethered to the indole nucleus. Restraining the morpholine diminished the ability of these pravadoline analogues to inhibit prostaglandin synthesis in vitro. In contrast, mouse vas deferens inhibitory activity was enhanced in [2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl] pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-(4-methoxyphenyl)methano ne (20). Only the R enantiomer of 20 was active (IC50 = 0.044 microM). An optimal orientation of the morpholine nitrogen for MVD inhibitory activity within the analogues studied was in the lower right quadrant, below the plane defined by the indole ring. A subseries of analogues of 20 and a radioligand of the most potent analogue, (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo [1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthalenyl)methanone (21) were prepared. Inhibition of radioligand binding in rat cerebellar membranes was observed to correlate with functional activity in mouse vas deferens preparations. Binding studies with this ligand (Win 55212-2) have helped demonstrate that the (aminoalkyl)indole binding site is functionally equivalent with the CP-55,940 cannabinoid binding site. These compounds represent a new class of cannabinoid receptor agonists.

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The present study describes the implementation of comparative molecular field analysis (CoMFA) to develop two 3D-QSAR (quantitative structure-activity relationship) models (CoMFA models 1 and 2) of the cannabimimetic (aminoalkyl)indoles (AAIs) for CB1 cannabinoid receptor binding affinity, based on pKi values measured using radioligand binding assays that displace two different agonist ligands, [3H]CP-55940 and [3H]WIN-55212-2. Both models exhibited a strong correlation between the calculated steric-electrostatic fields and the observed biological activity for the respective training set compounds. In light of the basicity of the morpholine nitrogen in the AAIs, separate CoMFA models were built for the AAIs as unprotonated and protonated species. Comparison of the statistical parameters resulting from these CoMFA models failed to provide unequivocal evidence as to whether the AAIs are protonated or neutral as receptor-bound species. Although the training sets of CoMFA model 1 and CoMFA model 2 differed with respect to composition and to the choice of displacement radioligand in each biological assay, their CoMFA StDevCoeff contour plots reveal similarities in terms of identifying those regions around the AAIs that are important for CB1 cannabinoid receptor binding such as the sterically favored region around the C3 aroyl group and the sterically forbidden region around the indole ring. When the experimental pKi values for the training set compounds to displace the AAI radioligand [3H]WIN-55212-2 were plotted against the pKi values as predicted for the same compounds to displace the cannabinoid radioligand [3H]CP-55940, the correlation was moderately strong (r = 0.73). However, the degree of correlation may have been lowered by the structural differences in the compounds comprising the training sets for CoMFA model 1 and CoMFA model 2. Taken together, the results of this study suggest that the binding site region within the CB1 cannabinoid receptor can accommodate a wide range of structurally diverse cannabimimetic analogues including the AAIs.

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We report the synthesis and in vitro biological activity of the nonpeptide bradykinin receptor antagonist WIN 64338, [[4-[[2-[[bis(cyclohexylamino) Bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) is a nonapeptide released from kininogens by the actions of plasma kallikreins (1) that has been implicated in a variety of physiological and pathological processes, including pain, inflammation, and regulation of blood pressure (2, 3). The effects of bradykinin are mediated through specific G-protein-coupled cell surface receptors (4). These receptors have been tentatively divided into at least three classes, B1, B2, and B3 (5-7), on the basis of pharmacological characterization with selective bradykinin peptide agonists and antagonists. Bradykinin binds to most putative B2 receptors with an affinity in the low nanomolar range under physiological conditions (8).A bradykinin analogue in which D-phenylalanine replaces L-proline in the 7 position of the native ligand was discovered by Vavrek and Stewart (9) and was found to be a bradykinin B2 receptor antagonist. A series of peptide analogues of bradykinin containing this substitution have demonstrated antagonist activity in a variety of tissues (10, 11). The D-Phe7-substituted bradykinin analogues were critical for initial receptor classification; however, they are generally of low potency in various biological assays and demonstrate partial or full agonist activity in certain tissues (12). In addition, these compounds are substrates for carboxypeptidase N (13). Cleavage of the C-terminal arginine by carboxypeptidase N results in compounds that are inactive at the bradykinin B2 receptor but active at the bradykinin B1 receptor (14).The structure and pharmacological activity of a different kind of bradykinin antagonist, DArg0-[Hyp3,Thi5,DTic7, Oic8lbradykinin (HOE-140) [Hyp, (4R)-4-hydroxyprolyl;Thi, 3-(2-thienyl)alanyl; DTic, 1,2,3,4-tetrahydroisoquinolin-2-yl-carbonyl; Oic, (3aS,7aS)-octahydroindol-2-yl-carbonylJ, has recently been described (15,16). In a variety of bradykinin assays, this compound acts as a selective B2 receptor antagonist and is at least two orders of magnitude more potent than any ofthe 18). Although HOE-140 appears to be a competitive antagonist of bradykinin at the B2 receptor in some biological assays, it is reported to be noncompetitive in other systems (19,20).Despite the increases in potency and biological activity observed in second-generation bradykinin receptor antagonists, these compounds are all peptides and therefore subject to metabolism and poor bioavailability (21 [[4-[[2-[[bis(cyclohexylamino) 4693The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.