Synthesis of potent oxindole CDK2 inhibitors

A series of oxindole CDK2 inhibitors was synthesized. These novel analogues have a saturated monosubstituted cyclic moiety at their C-4 position that mimics the ribofuranoside of ATP. This substitution afforded agents with increased potency relative to the parent indolinone and nanomolar range IC(50) against the CDK2 enzyme and two cancer cell lines.     

Effect of natural and synthetic benzyl benzoates on calmodulin

The present investigation describes the effect of the spasmolytic benzylbenzoates 1-9 from Brickellia veronicifolia on CaM using a functional in vitro enzymatic assay. Bovine brain PDE1 was used as a monitoring enzyme. The most active natural inhibitors of the system CaM-PDE1 were benzyl benzoates 3-5, which inhibited the activity of PDE1 in a concentration-dependent manner. In addition, three series of analogs of compound 4, compounds 10a-32a, were prepared and assayed. The benzyl benzoates from the first series, namely 10a-24a, possess no substituents on ring B but different number and position of hydroxyl or methoxy groups in ring A. The second group (25-32a), on the other hand, possesses an A ring identical to that on compound 4, but different substituents in Ring B. The most active compounds were 14a, 15a and 30a. These compounds were two to six times more potent than chlorpromazine, a well known CaM inhibitor. Benzyl benzoates 14a and 15a have methoxyl groups at C-2/C-4 and C-3/C-4 in ring A, respectively; while 30a, in addition to the methoxyl groups at C-2/C-6 of ring A, hold a benzoyloxy moiety at C-3' of ring B. Kinetic studies revealed that compounds 3, 4, 14a, 15a and 30a behave as competitive CaM antagonists.     

Substituted 2-(3′,4′,5′-trimethoxybenzoyl)-benzo[b]thiophene derivatives as potent tubulin polymerization inhibitors

The central role of microtubules in cell division and mitosis makes them a particularly important target for anticancer agents. On our early publication, we found that a series of 2-(3′,4′,5′-trimethoxybenzoyl)-3-aminobenzo[b]thiophenes exhibited strong antiproliferative activity in the submicromolar range and significantly arrested cells in the G2–M phase of the cell cycle and induced apoptosis.In order to investigate the importance of the amino group at the 3-position of the benzo[b]thiophene skeleton, the corresponding 3-unsubstituted and methyl derivatives were prepared. A novel series of inhibitors of tubulin polymerization, based on the 2-(3,4,5-trimethoxybenzoyl)-benzo[b]thiophene molecular skeleton with a methoxy substituent at the C-4, C-5, C-6 or C-7 position on the benzene ring, was evaluated for antiproliferative activity against a panel of five cancer cell lines, for inhibition of tubulin polymerization and for cell cycle effects. Replacing the methyl group at the C-3 position resulted in increased activity compared with the corresponding 3-unsubstituted counterpart. The structure–activity relationship established that the best activities were obtained with the methoxy group placed at the C-4, C-6 or C-7 position. Most of these compounds exhibited good growth inhibition activity and arrest K562 cells in the G2–M phase via microtubule depolymerization.     

Substituted 4-anilino-7-phenyl-3-quinolinecarbonitriles as Src kinase inhibitors

A series of substituted 4-anilino-7-phenyl-3-quinolinecarbonitriles has been prepared as Src kinase inhibitors. Optimal activity is observed with compounds that have basic amines attached via the para position of the 7-phenyl ring, and a hydrogen atom at the C-6 position. The best compounds are low nanomolar inhibitors of Src kinase, and have potent activity against Src-transformed fibroblast cells.     

Rational design and synthesis of novel thiazolidin-4-ones as non-nucleoside HIV-1 reverse transcriptase inhibitors

A series of novel thiazolidin-4-one analogues, characterized by different substitution patterns at positions C-2 and N-3 of the thiazolidin-4-one scaffold for anti-HIV-1 activity has been investigated. Most of the compounds showed anti-HIV-1 activity at micromolar concentrations when tested in TZM-bl cells in vitro. Among the thirty-three compounds tested, compound 16 was the most potent inhibitor of HIV-1 replication against HIV-1_IIIB, HIV-1_ADA5, HIV-1_UG070 and HIV-1_VB59 (EC₅₀ = 0.02, 0.08, 0.08 and 0.08 μM, respectively) with selectivity index (SI = 6940, 1735, 1692 and 1692) against tested viral strains, respectively. The results of the present study suggested that the substitution of the nitro group at 6′ position of the C-2 phenyl ring and 4,6-dimethylpyridin-2-yl at the N-3 position of thiazolidin-4-one had a major impact on the anti-HIV-1 activity and was found to lower cytotoxicity. The substitution of the heteroaryl ring with bromo group and bicyclic heteroaryl ring at N-3 thiazolidin-4-one was found to lower anti-HIV-1 activity and increase cytotoxicity. The undertaken docking studies thus facilitated the identification of crucial interactions between the HIV-1 RT enzyme and thiazolidin-4-one inhibitors, which can be used to design new potential inhibitors.     

Substituted benzyl-pyrimidines targeting thymidine monophosphate kinase of Mycobacterium tuberculosis: synthesis and in vitro anti-mycobacterial activity

A series of N(1)-(4-substituted-benzyl)-pyrimidines were synthesized as potential inhibitors of thymidine monophosphate kinase of Mycobacterium tuberculosis (TMPKmt). Key SAR parameters included the chain length substitution in para position of the benzyl ring, the functional group terminating the alkyl chain, and the substituent on the C-5 pyrimidine ring. Synthesized molecules were assayed against both recombinant enzyme and mycobacteria cultures. The most potent compounds have K(i) values in the micromolar range and an MIC(50) of 50microg/mL against Mycobacterium bovis. These results will guide the design of a new generation of lead compounds.     

Synthesis of nucleoside libraries on solid support. II. 2,6,8-Trisubstituted purine nucleosides using 8-bromoguanosine as precursor

A series of 2,6,8-trisubstituted purine nucleoside libraries was prepared by parallel solid-phase synthesis using 8-bromoguanosine as a common synthetic precursor. Polystyrene-methoxytrityl chloride resin was linked to the N2 or O5' position of the guanosine analogues. 8-Bromoguanosine was derivatized at the C8 position via carbon-carbon bond formation. Nucleophilic aromatic substitution at C2 and/or C6 positions with various amines produced two series of purine nucleoside libraries with very diverse substitution.     

Design, synthesis and activity of a potent, selective series of N-aryl pyridinone inhibitors of p38 kinase

A series of N-aryl pyridinone inhibitors of p38 mitogen activated protein (MAP) kinase were designed and prepared based on the screening hit SC-25028 (1) and structural comparisons to VX-745 (5). The focus of the investigation targeted the dependence of potency and metabolic stability on the benzyloxy connectivity, the role of the C-6 position and the substitution pattern on the N-phenyl ring. Further optimization produced the highly selective and potent pyridinones 2 and 3. These inhibitors exhibited activity in both acute and chronic models of inflammation.     

Enhanced potency dipeptide glycol renin inhibitors: studies in vitro and in the conscious rhesus

We prepared a series of novel dipeptide amides of the formula Boc-Phe-Leu-X, where X is a 3-amino-3-alkyl-1,2-propanediol with lower alkyl substitutions at C-1, in order to probe accessory binding sites in the enzyme renin. This approach was successful in generating potent inhibitors of human and hog renin in vitro. Moreover, these inhibitors were able to effect in vivo reduction of plasma renin activity (PRA) in the conscious salt-depleted rhesus monkey (i.v. route); this effect was related to the size of the C-1 alkyl group.     

Synthesis and testing of 5-benzyl-2,4-diaminopyrimidines as potential inhibitors of leishmanial and trypanosomal dihydrofolate reductase

Dihydrofolate reductase is a drug target that has not been thoroughly investigated in leishmania and trypanosomes. Work has previously shown that 5-benzyl-2,4-diaminopyrimidines are selective inhibitors of the leishmanial and trypanosome enzymes. Modelling predicted that alkyl/aryl substitution on the 6-position of the pyrimidine ring should increase enzyme activity of 5-benzyl-2,4-diaminopyrimidines as inhibitors of leishmanial and trypanosomal dihydrofolate reductase. Various compounds were prepared and evaluated against both the recombinant enzymes and the intact organisms. The presence of a substituent had a small or negative effect on activity against the enzyme or intact parasites compared to unsubstituted compounds.     

Synthesis and Testing of 5-Benzyl-2,4-diaminopyrimidines as Potential Inhibitors of Leishmanial and Trypanosomal Dihydrofolate Reductase

Dihydrofolate reductase is a drug target that has not been thoroughly investigated in leishmania and trypanosomes. Work has previously shown that 5-benzyl-2,4-diaminopyrimidines are selective inhibitors of the leishmanial and trypanosome enzymes. Modelling predicted that alkyl/aryl substitution on the 6-position of the pyrimidine ring should increase enzyme activity of 5-benzyl-2,4-diaminopyrimidines as inhibitors of leishmanial and trypanosomal dihydrofolate reductase. Various compounds were prepared and evaluated against both the recombinant enzymes and the intact organisms. The presence of a substituent had a small or negative effect on activity against the enzyme or intact parasites compared to unsubstituted compounds.     

Synthesis and antibacterial activity of 5-substituted oxazolidinones

A series of 5-substituted oxazolidinones with varying substitution at the 5-position of the oxazolidinone ring were synthesized and their in vitro antibacterial activity was evaluated. The compounds demonstrated potent to weak antibacterial activity. A novel compound (PH-027) demonstrated potent antibacterial activity, which is comparable to or better than those of linezolid and vancomycin against antibiotic-susceptible standard and clinically isolated resistant strains of gram-positive bacteria. Although the presence of the C-5-acetamidomethyl functionality at the C-5 position of the oxazolidinones has been widely claimed and reported as a structural requirement for optimal antimicrobial activity in the oxazolidinone class of compounds, our results from this work identified the C-5 triazole substitution as a new structural alternative for potent antibacterial activity in the oxazolidinone class.     

Synthesis and dopaminergic activity of a series of new 1-aryl tetrahydroisoquinolines and 2-substituted 1-aryl-3-tetrahydrobenzazepines

A series of new 1-aryl-6,7-dihydroxy tetrahydroisoquinolines with several substitution patterns in the 1-aryl group at C-1 were prepared in good yields. The influence of each substituent on the affinity and selectivity for D₁ and D₂ dopaminergic receptors was studied. Moreover, N-alkyl salts of these tetrahydroisoquinolines were used as starting material to synthesize a series of new 1-aryl-7,8-dihydroxy 3-tetrahydrobenzazepines derivatives with electron-withdrawing substituents at C-2 position by the diastereoselective Stevens rearrangement. The structure-activity relationship of these compounds was explored to evaluate the effect of the functional group at C-2 in benzazepines and the modification in the aryl group at the isoquinoline C-1 position towards the affinity and selectivity for the mentioned receptors. The 1-aryl-6,7-dihydroxy tetrahydroisoquinoline 4c shows significant affinity towards D₂ receptor, with K_i value of 31 nM. This significant affinity can be attributed to the presence of a thiomethyl group, and it is the most active 1-aryl-6,7-dihydroxy tetrahydroisoquinoline derivative reported to date.     

A new non-azole inhibitor of ABA 8'-hydroxylase: effect of the hydroxyl group substituted for geminal methyl groups in the six-membered ring

We designed and synthesized AHI4 that has an axial hydroxyl group instead of geminal methyl groups at C-6' of AHI1, previously reported as a lead compound for the development of non-azole inhibitors of ABA 8'-hydroxylase. (+)-AHI4 competitively inhibited 8'-hydroxylation of ABA by recombinant CYP707A3. The K(I) value was found to be 0.14 microM, 10-fold less than that of (+)-AHI1, suggesting that enzyme affinity increased by a factor of 10 due to substitution of the hydroxyl group by the geminal methyls at C-6'. This finding should assist in the design of more effective, non-azole ABA 8'-hydroxylase inhibitors.     

Aromatase inhibition by 4-thiosubstituted-4-androstene-3,17-dione derivatives

The synthesis and evaluation of 4-thiosubstituted-4-androstenedione analogs as inhibitors of estrogen synthetase (aromatase) is described. All compounds were prepared by the addition of various thiol reagents to 4 beta,5 beta-epoxyandrostanedione. Inhibitory activity of synthesized compounds was assessed using a human placental microsomal preparation as the enzyme source and [1 beta-3H]4-androstene-3,17-dione as substrate. Synthesized compounds exhibiting high inhibitory activity were further evaluated under initial velocity conditions to determine apparent Ki values. Several compounds were effective competitive inhibitors, and have apparent Ki values ranging from 34 to 52 nM, with the apparent Km for androstenedione being 54 nM. The results of these studies demonstrate a tightly fitted enzyme pocket that can accommodate bulky substituents at the C-4 position of androstenedione not to exceed 4.3 A in width and 5.5 A in length.     

Design of purine nucleoside phosphorylase inhibitors

Purine nucleoside phosphorylase inhibitors hold promise as specific immunosuppressive, anti-T cell leukemic, and antiuricopoietic agents. The best inhibitors available that are biologically active have Ki values from 10(-6) to 10(-7) M and fall into two categories: noncleavable nucleosides preferably iodinated at the C-5' position and C-8-substituted guanine or acycloguanosines. More potent inhibition is shown by phosphorylated acyclonucleosides that function as multisubstrate analogs, but these compounds are excluded from cells. The X-ray analysis of the human erythrocytic enzyme is beginning to reveal the nature of the active site and to explain the structure-activity relationships that have been established with analog substrates and inhibitors.     

New derivatives of silybin and 2,3-dehydrosilybin and their cytotoxic and P-glycoprotein modulatory activity

Large series of O-alkyl derivatives (methyl and benzyl) of silybin and 2,3-dehydrosilybin was prepared. Selective alkylation of the silybin molecule was systematically investigated. For the first time we present here, for example, preparation of 19-nor-2,3-dehydrosilybin. All prepared silybin/2,3-dehydrosilybin derivatives were tested for cytotoxicity on a panel of drugs sensitive against multidrug resistant cell lines and the ability to inhibit P-glycoprotein mediated efflux activity. We have identified effective and relatively non-cytotoxic inhibitors of P-gp derived from 2,3-dehydrosilybin. Some of them were more effective inhibitors at concentrations lower than a standard P-gp efflux inhibitor cyclosporin A. Another group of 2,3-dehydrosilybin derivatives also had better inhibitory effects on P-gp efflux but a cytotoxicity comparable with that of parent 2,3-dehydrosilybin. Structural requirements for improving inhibitory activity and reducing toxicity of 2,3-dehydrosilybin were established. Effect of E-ring substitution as well as an influence of the substituent size at the C-7-OH position of A-ring on P-gp-inhibitory activity was evaluated for the first time in this study.     

Chiral discrimination with regioselectively substituted cellulose esters as chiral stationary phases

Four kinds of cellulose derivatives, including two regioselectively substituted cellulose esters (6-O-acetyl-2,3-di-O-benzoyl cellulose and 2,3-di-O-acetyl-6-O-benzoyl cellulose), were synthesized so that the effects of their functional group distribution on their chiral discrimination ability could be examined. The degree of substitution by functional groups appeared to have a critical effect on the separation in most cases, but the type of the functional group at the C-6 position also significantly influenced chiral discrimination when a series of neutral arylalcohol derivatives were used as racemates. Copyright 2000 Wiley-Liss, Inc.     

Synthesis of C-6 substituted pyrazolo[1,5-a]pyridines with potent activity against herpesviruses

A novel series of potent C-6 substituted pyrazolo[1,5-a]pyridine inhibitors of herpes simplex viruses has been identified. A synthetic methodology was developed involving functionalization of a C-6 trifluoromethyl pyrazolo[1,5-a]pyridine to allow facile access to a diverse set of analogues from common late stage intermediates. The expansion of the SAR of this series at the 6 position allows for modifications to developability parameters such as clogP, while maintaining potency comparable to acyclovir.     

Heterocyclic inhibitors of dihydrodipicolinate synthase are not competitive

A series of piperidine- and pyridine-2,6-dicarboxylate derivatives has been evaluated as potential inhibitors of dihydrodipicolinate synthase (DHDPS). The compounds were designed with oxygen functionality at the C-4 position in order to mimic the putative enzyme product HTHDP. Most compounds displayed weak-moderate inhibition of DHDPS. Additionally, the most potent inhibitors were shown not to be competitive, indicating they do not bind at the active site. Discrepancies between the two common assay systems-the imidazole assay and the coupled assay-were observed which are attributed to inherent problems in the imidazole assay, leading to artefactually low K(i) measurements.