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The N-alkylation of primary nitrophenylsulfonamides followed by removal of the nitrophenylsulfonamide moiety under nucleophilic conditions to provide secondary amines has become an established literature procedure. Application of this methodology with less reactive alkylating agents can give rise to side products resulting from a nitrogen to carbon transfer of the nitrophenyl ring. This side product predominates when tetrabutylammonium hydroxide is used in place of metal carbonate bases in the N-alkylation step.

Polymer-supported quench methodology has been used for parallel purification of combinatorial libraries of dihydropyridones and their derivatives. The dihydropyridone scaffold was assembled via a solution phase Lewis acid catalyzed, herero-Diels-Alder reaction. Further modifications allow for the rapid generation of subsequent aminopiperidine and acyl-aminopiperidine libraries utilizing a library from library approach.

Two solid-supported synthesis strategies for the preparation of 3-thio-1,2,4-triazoles are described. In the first, Rink amide resin is combined with Fmoc-protected ω-amino acids, acid hydrazides, and alkyl halides to provide diverse sets of starting materials from which numerous triazoles may be prepared. The second employs t-alkylcarbamateresin (Boc resin) which permits the use of additional pools of starting materials, including isothiocyanates and α- and ω-amino esters, resulting in triazoles with patterns of functional groups that are not possible from the initial route. The combination of multiple resins and resin attachment sites allows the preparation of a diverse library based upon the3-thio-1,2,4-triazole scaffold and avoids the pitfallof having a single linker functionality present at the same position in all library members. General synthetic procedures and representative products from each route are presented. A similarity analysis of representative sublibraries from each synthesis strategy concludes that variation of the solid-phase linker chemistry and attachment site can enhance molecular diversity of the combined triazole library.

Solution and solid phase synthetic methods leading to the rapid, stereocontrolled construction of highly functionalized fused bicyclic amino acid derivatives have been developed. The key step involves a unique application of the intramolecular Pauson-Khand cyclization for the construction of hexahydro-1H-[2]pyrindinone ring systems. Further modifications which demonstrate the potential for combinatorial library generation are also disclosed.

A series of 5-[[1-(4'-carboxybenzyl)imidazolyl]methylidene]hydantoins have been prepared and evaluated as in vitro and in vivo angiotensin II (Ang II) antagonists. Variation of substituents on the hydantoin ring leads to potent and selective Ang II antagonists with nanomolar IC50 values at the AT1 receptor and negligible affinity for the AT2 receptor. Preferred substituents include an n-butyl at R1 and an alkyl or heteroarylmethyl substituent at R2. The selection of the R2 substituent was guided in part by the calculation of its log P since a significant correlation was observed between CLOGP and AT1 binding affinity. The biphenyl tetrazole pharmacophore, common to a number of AT1 antagonists, could be replaced by, for example, a 4-carbomethoxyphenyl substituent resulting in potent Ang II antagonists both in vitro and in vivo. A representative compound of this series is 57, which reduced the mean arterial blood pressure of renal hypertensive rats by 40% at 30 mg/kg po and by 25% at 10 mg/kg po. In addition this compound was efficacious in the salt-deplete normotensive monkey model maximally decreasing blood pressure 27% at 10 mg/kg po. In summary, these compounds belong to a novel class of Ang II antagonists that lack the biphenyl tetrazole moiety yet display appreciable and long lasting oral activity.

The primary and patent literature (through mid-1994) describing advances in AT2 receptor molecular biology and agents that interact with the angiotensin AT2 receptor subtype is reviewed. In vitro structure-activity relationships are summarised for both AT2-specific antagonists and balanced AT1/AT2 antagonists. Literature reports describing functional correlates for AT2 receptors are tabulated, and potential therapeutic utilities resulting from pharmacological intervention at AT2 receptors are discussed.

Syntheses and structure-activity relationships for a series of substituted tetrahydroisoquinoline-3-carboxylic acid derivatives with AT2-specific angiotensin II receptor binding inhibitory activity are reported.

A novel series of nonpeptide angiotensin II (AII) receptor antagonists containing a 1H-pyrrol-1-yl moiety at the 4-position of the imidazole have been developed. The pyrrole group occupies the same lipophilic pocket at the receptor as the chloro group in DuP 753 (68) and EXP 3174 (69) and the pentafluoro group in DuP 532 (70), respectively. The impetus for its selection came from bioisosteric considerations based on hydrophobic and electronic substituent constants. An extensive study of the structure-activity relationships revealed several highly potent AII receptor antagonists. An acyl substitution at the 2-position of the pyrrole ring improved activity, most notably in the in vivo rat model. In addition, the 2-substituted pyrrole compounds improved chemical stability toward extremely facile decarboxylation reaction associated with unsubstituted pyrrole analogues, thus facilitating development of these agents. The IC50's of 18, 20, and 42 (< 1 nM) were better than the reference compounds 69 and 70, respectively. These compounds were selective AII antagonists that compete at the AT1 receptor and showed no affinity at the AT2 receptor at concentrations up to 10 microM. Upon intravenous administration in a normotensive rat model, compound 18 inhibited the AII-induced responses with ED50 of 6 micrograms/kg per min. In a renal hypertensive rat model, the antihypertensive potency of compound 18, at a dose of 10 mg/kg, was very similar to those 68 and 69, respectively. Compound 18 demonstrated a dose-related (3-30 mg/kg) decrease in blood pressure that was sustained for greater than 24 h. On the basis of its profile, compound 18, designated as CI-996, has been selected for in-depth studies. The design, synthesis, in vitro, and in vivo structure-activity relationships are described.

Syntheses of radiolabeled, fluorescent and biotinyl probes with highly selective affinity for the angiotensin AT 2 receptor are described. The binding affinities at AT 2 and AT 1 receptors are reported.

Structure-activity relationships are reported for a novel class of 4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid derivatives that displace 125I-labeled angiotensin II from a specific subset of angiotensin II (Ang II) binding sites in rat adrenal preparations. This binding site is not the Ang II receptor mediating vascular contraction or aldosterone release, but, rather, is one whose function has not yet been fully elucidated. It has been identified in a number of tissues and has a similar affinity for Ang II and its peptide analogues as does the vascular receptor. The non-peptide compounds reported here are uniquely specific in displacing Ang II at this binding site and are inactive in antagonizing Ang II at the vascular receptor or in pharmacological assays measuring vascular effects. PD 123,319 (79), one of the most potent compounds, has an IC50 of 34 nM. Certain of these compounds may have utility in the definition and study of Ang II receptor subtypes.

Optimization of a 2-step reaction sequence was accomplished in 3-4 days, with over 200 different reaction conditions evaluated. Combinatorial arrays were performed using the optimized conditions to synthesize 590 new compounds which were tested for inhibition against N-His (D381E) ICE. Thirty-five compounds showed at least a tenfold improvement in activity compared to an initial standard.

Mutational activation of ras has been found in many types of human cancers, including a greater than 50% incidence in colon and about 90% in pancreatic carcinomas. The activity of both native and oncogenic ras proteins requires a series of post-translational processing steps. The first event in this process is the farnesylation of a cysteine residue located in the fourth position from the carboxyl terminus of the ras protein, catalyzed by the enzyme farnesyltransferase (FTase). Inhibitors of FTase are potential candidates for development as antitumor agents. Through a high-volume screening program, the pentapeptide derivative PD083176 (1), Cbz-His-Tyr(OBn)-Ser(OBn)-Trp-DAla-NH2, was identified as an inhibitor of rat brain FTase, with an IC 50 of 20 nM. Structure-activity relationships were carried out to determine the importance of the side chain and chirality of each residue. This investigation led to a series of potent FTase inhibitors which lack a cysteine residue as found in the ras peptide substrate. The parent compound (1) inhibited the insulin-induced maturation of Xenopus oocytes (concentration : 5 pmol/oocyte), a process which is dependent on the activation of the ras pathway.

Five renin inhibitors were cocrystallized with endothiapepsin, a fungal enzyme homologous to renin. Crystal structures of inhibitor-bound complexes have provided invaluable insight regarding the three-dimensional structure of the aspartic proteinase family of enzymes, as well as the steric and polar interactions that occur between the proteins and the bound ligands. Beyond this, subtleties of binding have been revealed, including multiple subsite binding modes and subsite interdependencies. This information has been applied in the design of novel potent renin inhibitors and in the understanding of structure-activity relationships and enzyme selectivities.

A series of renin inhibitors containing ester side chains at the P2 subsite are potent inhibitors of primate renin. Derivatives containing the diol isostere (ACDMH) at P1-P1' were the most potent inhibitors. Moderate selectivity for renin was observed relative to the closely related aspartic proteinase cathepsin D. The prototype compound, 4 (PD 132002), inhibited pepsin only weakly. In both high-renin normotensive and high-renin renal hypertensive monkeys, 4 produced substantial reductions in blood pressure after oral administration of 30 mg/kg. The maximum drop in blood pressure observed (24 +/- 4 mmHg) in the renal hypertensive monkey model was comparable to the drop produced by an intravenous infusion of saralasin at a maximally effective dose. Both the magnitude and duration of the oral antihypertensive effect of 4 is greater than that produced by enalkiren, CGP-38560, or CP-80794 by direct comparison in the same hypertensive monkey model. The malonate ester derivatives were prepared as ca. 65:35 mixtures of epimers. The kinetics of epimerization of 4 were investigated in detail, and it was shown to equilibrate rapidly at physiological pH (t1/2 less than 2 min). Fractional crystallization was employed to obtain the individual diastereomers in greater than 98% purity, which were indistinguishable in terms of their activity in vitro or in vivo, presumably due to rapid epimerization under the testing conditions.

A series of 1-substituted mitosene analogues of the mitomycin antitumor antibiotics was prepared by total synthesis and screened for activity against P388 leukemia in mice. In general, analogues with moderately good leaving groups (mostly esters) at the 1 position were active, whereas analogues without such substituents were inactive or barely active. These results lend support to the idea that mitosenes with leaving groups at position 1 are capable of bifunctional alkylation of DNA in a manner similar to that of mitomycin C. The most active mitosenes were equal in potency (minimum effective dose) to a corresponding aziridinomitosene, but they were less effective in prolonging life span.