Synthesis of thiophenecarboxamides, thieno[3,4-c]pyridin-4(5H)-ones and thieno[3,4-d]pyrimidin-4(3H)-ones and preliminary evaluation as inhibitors of poly(ADP-ribose)polymerase (PARP)

Inhibitors of poly(ADP-ribose)polymerase (PARP) inhibit repair of damaged DNA and thus potentiate radiotherapy and chemotherapy of cancer. Treatment of 3-cyanothiophene with potassium nitrate and concentrated sulphuric acid gave 5-nitrothiophene-3-carboxamide. 4-Nitrothiophene-2-carboxamide and 5-nitrothiophene-2-carboxamide were formed similarly from 2-cyanothiophene. Reduction with tin(II) chloride gave the corresponding aminothiophenecarboxamide salts which were isolated via their N-Cbz derivatives. Lithiation of 3,4-dibromothiophene at -116 degrees C and quenching with alkyl chloroformates gave 4-bromothiophene-3-carboxylates, which were hydrolysed to 4-bromothiophene-3-carboxylic acid. Hurtley reactions with the enolates of pentane-2,4-dione and of 1-phenylbutane-1,3-dione, followed by acyl cleavage, led to 4-(2-oxopropyl)thiophene-3-carboxylic acid and 4-phenacylthiophene-3-carboxylic acid, respectively. Condensation with ammonia in acetic acid gave 6-methyl- and 6-phenylthieno[3,4-c]pyridin-4-ones, which were selectively nitrated at the 1- and 7-positions or were dinitrated. Ethyl 4-acetamido- and 4-benzamido-thiophene-3-carboxylates were cyclised to 2-methyl- and 2-phenyl-thieno[3,4-d][1,3]oxazin-4-ones, respectively. Ring-opening with ammonia and recyclisation led to 2-substituted thieno[3,4-d]pyrimidin-4-ones. The aminothiophenecarboxamides are analogues of 3-aminobenzamide, a selective inhibitor of poly(ADP-ribose)polymerase (PARP); the thienopyridinones and the thienopyrimidinones are analogues of isoquinolin-1-ones and quinazolin-4-ones, respectively, which inhibit this enzyme. In preliminary assays, several thienopyridinones and thienopyrimidinones showed potent inhibitory activity against PARP.     

Synthesis and muscarinic receptor pharmacology of a series of 4,5,6,7-tetrahydroisothiazolo[4,5-c]pyridine bioisosteres of arecoline.

A series of O- and ring-alkylated derivatives of 4,5,6,7-tetrahydroisothiazolo[4,5-c]pyridin-3-ol was synthesized via treatment of appropriately substituted 4-benzylamino-1,2,5,6-tetrahydropyridine-3-carboxamides with hydrogen sulfide and subsequent ring closure by oxidation with bromine. The muscarinic receptor affinity as well as estimated relative efficacy and subtype selectivity of this series of bicyclic arecoline bioisosteres were determined using rat brain membranes and a number of tritiated muscarinic receptor ligands. The effects at the five cloned human muscarinic receptor subtypes of a selected series of chiral analogues, with established absolute stereochemistry, were studied using receptor selection and amplification technology (R-SAT). The potency, relative efficacy, and receptor subtype selectivity of these compounds were related to the structure of the O-substituents and the position and stereochemical orientation of the piperidine ring methyl substituents.     

C-nucleoside analogues of furanfurin as ligands to A1 adenosine receptors

Furanfurin (2-beta-D-ribofuranosylfuran-4-carboxamide) derivatives and analogues were synthesized and their affinity for adenosine receptors was determined. The agonistic behavior of furanfurin against A1 receptors is preserved only when the furan ring is substituted with isosteric pentatomic ring systems such as oxazole, thiazole or thiophene, and the carboxamide group is unsubstituted. Replacement of the hydrogen atoms of the carboxamide group with alkyl, cycloalkyl or arylalkyl groups generates compounds endowed with moderate antagonistic activity.     

Synthesis and biological evaluation of some novel triazol-3-ones as antimicrobial agents

A new series of triazol-3-one derivatives bearing 4-methyl-4H-thieno[3',2': 5,6]thiopyrano[4,3-d][1,3]thiazolyl or 4-(thiophene-3-yl) thiazolyl moiety at 4-position and alkyl substitution at 2-position are synthesized. All the synthesized compounds are characterized by elemental analysis, IR, (1)H NMR, (13)C NMR, and mass spectral data. The newly synthesized compounds are screened for antifungal and antibacterial activities.     

Discovery of N-ethylpyridine-2-carboxamide derivatives as a novel scaffold for orally active γ-secretase modulators

Gamma-secretase modulators (GSMs) are promising disease-modifying drugs for Alzheimer’s disease because they can selectively decrease pathogenic amyloid-β42 (Aβ42) levels. Here we report the discovery of orally active N-ethylpyridine-2-carboxamide derivatives as GSMs. The isoindolinone moiety of 5-[8-(benzyloxy)-2-methylimidazo[1,2-a]pyridin-3-yl]-2-ethyl-2,3-dihydro-1H-isoindol-1-one hydrogen chloride (1a) was replaced with a picolinamide moiety. Optimization of the benzyl group significantly improved GSM activity and mouse microsomal stability. 5-{8-[([1,1′-Biphenyl]-4-yl)methoxy]-2-methylimidazo[1,2-a]pyridin-3-yl}-N-ethylpyridine-2-carboxamide hydrogen chloride (1v) potently reduced Aβ42 levels with an IC₅₀ value of 0.091 µM in cultured cells without inhibiting CYP3A4. Moreover, 1v demonstrated a sustained pharmacokinetic profile and significantly reduced brain Aβ42 levels in mice.     

SYNTHESIS AND BIOLOGICAL EVALUATION OF PYRIDIN-2-ONE NUCLEOSIDES

The synthesis of 1-(β-D-ribofuranosyl)pyridin-2-one-3-carboxylic acid and the 3-carboxamide as well as a short series of 3N-carboxamides, prepared by TPTU/HOBt coupling of primary amines with 1-(β-D-ribofuranosyl)pyridin-2-one-3-carboxylic acid, and their evaluation as anti-infective agents is described.     

Synthesis of thiophenes and thieno[3,2-c]pyran-4-ones as antileishmanial and antifungal agents

A series of highly functionalized thiophene (2) and thieno[3,2-c]pyran-4-one(4) derivatives have been synthesized and evaluated for their antileishmanial and antifungal activities.     

A new synthesis of certain 7-(beta-D-ribofuranosyl) and 7-(2-deoxy-beta-D-ribofuranosyl) derivatives of 3-deazaguanine via the sodium salt glycosylation procedure.

A facile synthesis of 7-beta-D-ribofuranosyl-3-deazaguanine (1) and certain 8-substituted derivatives of 1 via the sodium salt glycosylation method has been developed. Glycosylation of the sodium salt of methyl 2-chloro(or methylthio)-4(5)-cyanomethylimidazole-5(4)-carboxylate (5 and 13b) with 2,3,5-tri-O-benzoyl-D-ribofuranosyl bromide (6) gave exclusively methyl 2-chloro(or methylthio)-4-cyanomethyl-1-(2,3, 5-tri-O-benzoyl-beta-D-ribofuranosyl)imidazole-5-carboxylate (7 and 14a), respectively. Ammonolysis of 7 and 14a provided 6-amino-2-chloro(or methylthio)-3-beta-D-ribofuranosylimidazo-[4,5-c]pyridin-4(5H)-one (11 and 17), which on subsequent dehalogenation (or dethiation) gave 1. Similarly, reaction of the sodium salt of 5 and 13b with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-D-erythro-pentofuranose (8), and ammonolysis of the glycosylated imidazole precursors (9 and 16) gave 6-amino-2-chloro(or methylthio)-3-(2-deoxy-beta-D-erythro-pentofuranosyl) imidazo[4,5-c]-pyridin-4(5H)-one (10a and 15), respectively. Dehalogenation of 10a or dethiation of 15 gave 2'-deoxy-7-beta-D-ribofuranosyl-3-deazaguanine (10b). This procedure provided a direct method of obtaining 10b without the contaminating 9-glycosyl isomer 4.     

Design, synthesis, and thrombin-inhibitory activity of pyridin-2-ones as P2/P3 core motifs

Guided by available X-ray crystal structure data on the serine protease thrombin, a series of pyridin-2-one derivatives were designed and synthesized having diverse functionality at the P(1) and P(3) sites. Potent in vitro activity against thrombin, with excellent selectivity over trypsin was found for selected analogues.     

Structure-activity relationship, kinetic mechanism, and selectivity for a new class of ubiquitin C-terminal hydrolase-L1 (UCH-L1) inhibitors

3-Amino-2-keto-7H-thieno[2,3-b]pyridin-6-one derivatives were discovered as moderately potent inhibitors of ubiquitin C-terminal hydrolase-L1 (UCH-L1) utilizing an assay that measures hydrolysis of the fluorogenic substrate Ub-AMC. SAR studies revealed that both the carboxylate at the 5-position and the 6-pyridone ring were critical for inhibitory activity. Furthermore, activity was dependent on the nature of the ketone substituent at the 2-position, with 4-Me-Ph and 2-naphthyl being best. Kinetic mechanism studies revealed that these compounds were uncompetitive inhibitors of UCH-L1, binding only to the Michaelis-complex and not to free enzyme. The active compounds were selective for UCH-L1, exhibiting neither inhibition of other cysteine hydrolases (e.g., UCH-L3, papain, isopeptidase T, caspase-3, and tissue transglutaminase) nor cytotoxicity in N2A cells.     

Synthesis of 6-(2-thienyl)purine nucleoside derivatives toward the expansion of the genetic code.

Unnatural bases specifically pairing with pyridin-2-one, 2-amino-6-(2-thienyl) purine and 2-amino-6-(2-furanyl)purine, were newly designed to replace 2-amino-6-(N,N-dimethylamino)purine. It was expected that these novel purine analogues, as compared with 2-amino-6-(N,N-dimethylamino)purine, might reduce the interference in the stacking interactions with the neighboring bases in a duplex and improve the efficiency of the enzymatic incorporation of the nucleoside triphosphate of pyridin-2-one opposite these unnatural bases. The syntheses of these nucleoside derivatives and the DNA fragments were examined.     

2''-Deoxy-3,7-dideazaguanosine and related compounds. Synthesis of 6-amino-1-(2-deoxy-beta-D-erythro-pentofuranosyl) and 1-beta-D-arabinofuranosyl-1H-pyrrolo[3,2-c]pyridin-4(5H)-one via direct glycosylation of a pyrrole precursor.

The synthesis of two new analogs of 2'-deoxyguanosine, 6-amino-1-(2-deoxy-beta-D-erythro-pentofuranosyl)-1H-pyrrolo[3,2-c] pyridin-4(5H)-one (8) and 6-amino-1-beta-D-arabinofuranosyl-1H-pyrrolo[3,2-c]-pyridin-4(5H)-one (13) has been accomplished by glycosylation of the sodium salt of ethyl 2-cyanomethyl-1H-pyrrole-3-carboxylate (4c) using 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-D-erythro-pentofuranose( 5) and 1-chloro-2,3,5-tri-O-benzyl-alpha-D-arabinofuranose (9), respectively. The resulting blocked nucleosides, ethyl 2-cyanomethyl-1-(2-deoxy-3,5-di-O-p-toluoyl-beta-D-erythro- pentofuranosyl)-1H-pyrrole-3-carboxylate (6) and ethyl 2-cyanomethyl-1-(2,3,5-tri-O-benzyl-beta-D-arabinofuranosyl)- 1H-pyrrole-3-carboxylate, were ring closed with hydrazine to form 5-amino-6-hydrazino-1-(2-deoxy-beta-D-erythro-pentofuranosyl)-1H- pyrrolo[3,2-c]-pyridin-4(5H)-one (7) and 5,6-diamino-1-(2,3,5-tri-O-benzyl-beta-D-arabinofuranosyl)-1H- pyrrolo[3,2-c]pyridin-4(5H)-one (11), respectively. Treatment of 7 with Raney nickel provided the 2'-deoxyguanosine analog 8 while reaction of 11 with Raney nickel followed by palladium hydroxide/cyclohexene treatment gave the 2'-deoxyguanosine analog 13. The anomeric configuration of 8 was assigned as beta by proton NMR, while that of 13 was confirmed as beta by single-crystal X-ray analysis of the deblocked precursor ethyl 2-cyanomethyl-1-beta-D-arabinofuranosyl-1H-pyrrole-3-carboxylate (10a).     

Synthesis and cholinesterase inhibitory activity of new 2-benzofuran carboxamide-benzylpyridinum salts

A series of benzofuran-2-carboxamide-N-benzyl pyridinium halide derivatives (6a-o) are synthesized as new cholinesterase inhibitors. The synthetic pathway involves the reaction of salicylaldehyde derivatives and ethyl bromoacetate, followed by hydrolysis and amidation with 3- and 4-picolyl amine. Subsequently, N-((pyridin-4-yl) methyl) benzofuran-2-carboxamide and substituted N-((pyridin-3-yl) methyl) benzofuran-2-carboxamides reacts with benzyl halides to afford target compounds (6a-o). The chemical structures of all derivatives were confirmed by spectroscopic methods. The studies reveal that some of the synthesized compounds are potent butyrylcholinesterase inhibitors with IC₅₀ values in the range of 0.054–2.7 µM. In addition, good inhibitory effects on Aβ self-aggregation are observed for 6h and 6k (33.1 and 46.4% at 100 µM, respectively).     

s-Cis and s-trans isomerism of the His-Pro peptide bond in angiotensin and thyroliberin analogues.

The dipeptide His-Pro isomerizes from all-s-trans to partly s-cis when titrated in D2O from acidic to neutral pD as observed by 13C and 1H nuclear magnetic resonance of the proline side chain. This isomerization is reported by the His C-2 and C-4 protons and carbons which show distinct, well-resolved resonances for each isomer. The influence of the His-Pro peptide bond rotational state on the histidine protons far removed from the bond has not been previously observed in model compounds or peptides. The peptides thyroliberin (TRH), [3-MeHis2]-TRH, and [3-MeHis6]-, [Sar1,Al8]-, and Nalpha-acetylangiotensin II were found to similarly isomerize from all-s-trans to partly s-cis as reported by their His C-2 and C-4 proton resonances. The His C-2 and C-4 protons in the peptides [1,3-diMeHis2]-TRH and [1-MeHis6]-, and [homoHis6]-angiotensin do not report this isomerization. Angiotensin II has previously been found to exhibit the same isomerization. The reporting of the s-trans to s-cis isomerization by the His C-2 proton appears to be correlated with the known potencies of the five angiotensin peptides in rat uterine strips and of the three TRH peptides by radioimmunoassay of released thyrotropin.     

Structure and conformation of 1-beta-D-ribo furanosyl pyridin-2-one-5-carboxamide: an anti-inflammatory agent

The pyrimidine nucleoside, 1-beta-D-ribofuranosyl pyridine-2-one-5-carboxamide, is an anti inflammatory agent used in the treatment of adjuvant-induced arthritis. It is the 2-one isomer of 1-beta-D-ribofuranosyl pyridine-4-one 5-carboxamide, an unusual nucleoside isolated from the urine of patients with chronic myelogenic leukemia and an important cancer marker. Crystals of 1-beta-D-ribofuranosyl pyridine-2-one-5-carboxamide are monoclinic, space group C2, with the cell dimensions a = 31.7920(13), b = 4.6872 (3), c = 16.1838(11), beta = 93.071(3) degrees , V = 2408.2(2) A(3), D(calc) = 1.496 mg/m(3) and Z = 8 (two molecules in the asymmetric unit). The structure was obtained by the application of direct methods to diffractometric data and refined to a final R value of 0.050 for 1669 reflections with I >or= 3sigma. The nucleoside exhibits an anti conformation across the glycosidic bond (chi(CN) = -15.5 degrees , -18.9 degrees ), a C3 '-endo C2 '-exo [(3)(2)T] ribose pucker and g(+) across the C(4 ')-C(5 ') exocyclic bond. The amino group of the carboxamide group is distal from the 2-one and lacks the intramolecular hydrogen bonding found in the related 2-one molecule. Nuclear magnetic resonance studies shows also an anti conformation across the glycosidic bond but the solution conformation of the furanose ring is not the same as that found in the solid state.     

Nucleosides and Nucleotides. 98. Synthesis and Antitumor Activities of 5-Ethynylimidazole-4-carboxamide and -carbonitrile Derivatives

Abstract

5-Ethynyl-1-(2-deoxy-β-D-ribofuranosyl)imidazole-4-carbonitrile (4) and -carboxamide (5) and 5-ethynyl-1-(5-deoxy-β-D-ribofuranosyl)imidazole-4-carbonitrile (11) and -carboxamide (12) have been synthesized from the corresponding 5-iodo derivatives 2 and 7 by a palladium-catalyzed cross-coupling reaction with (tri-methylsilyl)acetylene. The aglycons, 5-ethynylimidazole derivatives 14 and 15 were synthesized by the hydrolytic cleavage of the corresponding nucleosides. The antileukemic activity of these nucleosides and base analogues are also described.     

Degradation of thiophene-2-carboxylate,furan-2-carboxylate,pyrrole-2-carboxylate and other thiophene derivatives by the bacterium Vibrio YC1

Summary A bacterium of the genus Vibrio, capable of degrading thiophene derivatives, was isolated from enrichment cultures inoculated with oil-contaminated estuarine mud. Of the thiophene derivatives tested, only thiophene-2-carboxylate (T2C), thiophene-2-acetate and thiophene-2-carbonyl chloride supported growth, but a total of seven were significantly oxidised by resting cells. Furan-2-carboxylate (F2C) and pyrrole-2-carboxylate (P2C) also supported growth and were oxidised. The heteroatoms of T2C and P2C were released into the media as sulphate and ammonia and served as sole sources of sulphur and nitrogen for growth. Mutants defective in T2C utilisation (Thc^–) were isolated, many being also defective in F2C and P2C utilisation.Offprint requests to: J. S. Evans     

Sequence specificity of the binding of 9-aminoacridine- and amsacrine-4-carboxamides to DNA studied by DNase I footprinting.

DNase I footprinting has been used to probe the sequence selectivity of binding of a series of intercalating amsacrine-4-carboxamides and a related 9-aminoacridine-4-carboxamide to three DNA restriction fragments. These ligands have good experimental antileukemic activity, and for those members of the series that gave evaluable footprints, our principal finding is that they bind preferentially to GC-rich regions in agreement with the conclusion of equilibrium and kinetic measurements. The highest affinity sites generally occur in clusters of GC base pairs with runs of AT pairs being excluded from binding. It is important to appreciate that the 9-aminoacridine- and amsacrine-4-carboxamides exhibit a very high degree of selectivity for GC sites which, to our knowledge, has not been previously matched by acridine derivatives in footprinting experiments. The principal determinant of specificity appears to be the 4-carboxamide group itself since neither variations in the terminal funtionality of the 4-carboxamide sidechain nor the presence of the 9-anilino substituent modifies sequence preferences. The molecular origins of selectivity may be discerned in terms of potential hydrogen bonding interactions between the 4-carboxamide moiety and carbonyl oxygen and amino groups of GC base pairs in the DNA minor groove at CG dinucleotide sites. The related therapeutic agent amsacrine failed to inhibit cleavage by DNase I, so no conclusion can be drawn concerning its binding selectivity, save to note that amsacrine does not possess the 4-carboxamide group which appears to be the crucial determinant of GC specificity. Whether selectivity for binding to GC-rich sequences is an important element in the antitumor activity of both the 9-aminoacridine- and amsacrine-4-carboxamides remains to be determined.     

Synthesis and biological evaluation of new 3-substituted indole derivatives as potential anti-inflammatory and analgesic agents

Treatment of 3-cyanoacetyl indole 1 with the diazonium salts of 3-phenyl-5-aminopyrazole and 2-aminobenzimidazole afforded the corresponding hydrazones 4 and 5. 3-Cyanoacetyl indole reacted with phenylisothiocyanate to give the corresponding thioacetanilide derivative 7. Treatment of 7 with hydrazonoyl chlorides afforded the corresponding 1,3,4-thiadiazole derivatives 8a-f and 9. Also, the thioacetanilide reacted with alpha-haloketones to afford thiophene derivatives 10a,b (tenidap analogues), or thiazolidin-4-one derivative 11. The newly synthesized compounds were found to possess potential anti-inflammatory and analgesic activities.     

Synthesis and profiling of a 3-aminopyridin-2-one-based kinase targeted fragment library: Identification of 3-amino-5-(pyridin-4-yl)pyridin-2(1H)-one scaffold for monopolar spindle 1 (MPS1) and Aurora kinases inhibition

Screening a 3-aminopyridin-2-one based fragment library against a 26-kinase panel representative of the human kinome identified 3-amino-5-(1-methyl-1H-pyrazol-4-yl)pyridin-2(1H)-one (2) and 3-amino-5-(pyridin-4-yl)pyridin-2(1H)-one (3) as ligand efficient inhibitors of the mitotic kinase Monopolar Spindle 1 (MPS1) and the Aurora kinase family. These kinases are well recognised as attractive targets for therapeutic intervention for treating cancer. Elucidation of the binding mode of these fragments and their analogues has been carried out by X-ray crystallography. Structural studies have identified key interactions with a conserved lysine residue and have highlighted potential regions of MPS1 which could be targeted to improve activity and selectivity.