Benzopyranones with retro-amide side chains as (inhibitory) beta-lactamase substrates

3-(N-Benzylcarbamoyl)-7-carboxy-3, 4-dihydro-2H-1-benzo-pyran-2-one and its 8-carboxy analogue have been synthesized and evaluated as potential (inhibitory) substrates of beta-lactam-recognizing enzymes. These compounds are bicyclic delta-lactones with retro-amide (with respect to classical beta-lactams) side chains. They were found to be comparably effective as substrates of typical class A, C and D beta-lactamases as analogous benzopyranones bearing 'normal' amide side chains. The new 8-carboxy derivative, however, formed a much more (1000-fold) tightly-bound acyl-enzyme with a class C beta-lactamase than did its 'normal' analogue, and thus provides a structural lead to new inhibitors of this class of beta-lactamase.     

Synthesis and beta-lactamase reactivity of alpha-substituted phenaceturates

Beta-lactams with 6alpha (penicillins) or 7alpha (cephalosporins) substituents are often beta-lactamase inhibitors. This paper assesses the effect of such substituents on acyclic beta-lactamase substrates. Thus, a series of m-carboxyphenyl phenaceturates, substituted at the glycyl alpha-carbon by -OMe, -CH(2)OH, -CO(2)(-), and -CH(2)NH(3)(+), have been prepared, and tested for their reactivity against serine beta-lactamases. The latter two are novel substituents in beta-lactamase substrates. The methoxy and hydroxymethyl compounds were found to be poor to moderately good substrates, depending on the enzyme. The aminomethyl compound gave rise to a transiently stable (t(1/2)=4.6s) complex on its reaction with a class C beta-lactamase. The reactivity of the compounds against three low molecular weight DD-peptidases was also tested. Again, the methoxy and hydroxymethyl compounds proved to be quite good substrates with no sign of inhibitory complexes. The DD-peptidases reacted with one enantiomer (the compounds were prepared as racemates), presumably the D compound. The class C beta-lactamase reacted with both D and L enantiomers although it preferred the latter. The structural bases of these stereo-preferences were explored by reference to the crystal structure of the enzyme by molecular modeling studies. The aminomethyl compound was unreactive with the DD-peptidases, whereas the carboxy compound did not react with any of the above-mentioned enzymes. The inhibitory effects of the -OMe and -CH(2)OH substituents in beta-lactams apparently require a combination of the substituent and the pendant leaving group of the beta-lactam at the acyl-enzyme stage.     

Potential inhibitors of angiogenesis. Part II: 3-(azolylmethylene)-2,3-dihydrobenzo[b]furan-2-ones

The synthesis and pharmacological evaluation of new 3-(imidazol-4(5)-ylmethylene)-2,3-dihydrobenzo[b]furan-2-ones 8-10 and 3-(3,5-dimethylpyrrol-2-ylmethylene)-2,3-dihydrobenzo[b]furan-2-one 11, analogues of SU-5416, as potential inhibitors of angiogenesis, are reported. Compounds 8 and 11 were prepared by a Knoevenagel reaction starting from 2-hydroxyphenylacetic acid 2 and 4-formylimidazole 5 or 2-formyl-3,5-dimethylpyrrole 7, followed by acid-catalysed cyclodehydration. For compounds 9 and 10, an alternative method was used; it consisted in carrying out the Knoevenagel reaction with the 2,3-dihydrobenzo[b]furan-2-ones 3 and 4. The antiangiogenic activity of these compounds was evaluated in the three-dimensional in vitro rat aortic rings test at 1microM. At this concentration, compound 11 induced a decrease of angiogenesis comparable to that observed with SU-5416; the vascular density index at 1 microM of 11 and SU-5416 were 30 +/- 10 and 22 +/- 4% of control, respectively.     

Synthesis and primary cytotoxicity evaluation of arylmethylenenaphthofuranones derivatives

New series of 2(or 3)-arylmethylenenaphtho[2,1-b]furan-3(or 2)-ones were synthesized, characterized and tested for anticancer properties in vitro. The target compounds were prepared by Knoevenagel coupling between the naphthofuranones 3, 28-30 and formyl derivatives. 2-(4-Oxo-1-benzopyran-3-ylmethylene)naphtho[2,1-b]furan-3-one 36 was the most active compound (IC50 (L1210) = 1.6 microM). These compounds were also evaluated, in an independent manner, as inhibitors of Src protein tyrosine kinase, but only minor activity was observed.     

Antiprogestational agents. The synthesis of 7-alkyl steroidal ketones with anti-implantational and antidecidual activity

A series of 7α- and 7β- alkyl derivatives of steroidal 4-en- and 5-en-3-ones were prepared by 1,6-conjugate addition of organocopper reagents to various steroidal 4,6-dien-3-ones of the androstane, estrane and gonane series. Biological study of these and related compounds revealed that 17β-hydroxy-7α-methyl-5-androsten-3-one (2), 17β-hydroxy-7α-methyl-5-estren-3-one acetate and 17β-hydroxy-7α-methyl-4-estren-3-one acetate had significant anti-implantational and antidecidual activities. The contragestative effects were associated with the latter antihormonal properties, and not with the androgenicity of these compounds.     

Structure-based design guides the improved efficacy of deacylation transition state analogue inhibitors of TEM-1 beta-Lactamase(,)

Transition state analogue boronic acid inhibitors mimicking the structures and interactions of good penicillin substrates for the TEM-1 beta-lactamase of Escherchia coli were designed using graphic analyses based on the enzyme's 1.7 A crystallographic structure. The synthesis of two of these transition state analogues, (1R)-1-phenylacetamido-2-(3-carboxyphenyl)ethylboronic acid (1) and (1R)-1-acetamido-2-(3-carboxy-2-hydroxyphenyl)ethylboronic acid (2), is reported. Kinetic measurements show that, as designed, compounds 1 and 2 are highly effective deacylation transition state analogue inhibitors of TEM-1 beta-lactamase, with inhibition constants of 5.9 and 13 nM, respectively. These values identify them as among the most potent competitive inhibitors yet reported for a beta-lactamase. The best inhibitor of the current series was (1R)-1-phenylacetamido-2-(3-carboxyphenyl)ethylboronic acid (1, K(I) = 5.9 nM), which resembles most closely the best known substrate of TEM-1, benzylpenicillin (penicillin G). The high-resolution crystallographic structures of these two inhibitors covalently bound to TEM-1 are also described. In addition to verifying the design features, these two structures show interesting and unanticipated changes in the active site area, including strong hydrogen bond formation, water displacement, and rearrangement of side chains. The structures provide new insights into the further design of this potent class of beta-lactamase inhibitors.     

Synthesis and primary cytotoxicity evaluation of arylmethylenenaphthofuranones derivatives

New series of 2(or 3)-arylmethylenenaphtho[2,1-b]furan-3(or 2)-ones were synthesized, characterized and tested for anticancer properties in vitro. The target compounds were prepared by Knoevenagel coupling between the naphthofuranones 3, 28–30 and formyl derivatives. 2-(4-Oxo-1-benzopyran-3-ylmethylene)naphtho[2,1-b]furan-3-one 36 was the most active compound (IC₅₀ (L1210) = 1.6 μM). These compounds were also evaluated, in an independent manner, as inhibitors of Src protein tyrosine kinase, but only minor activity was observed.     

Potential Inhibitors of Angiogenesis. Part II: 3-(Azolylmethylene)-2,3-dihydrobenzo[b]furan-2-ones

The synthesis and pharmacological evaluation of new 3-(imidazol-4(5)-ylmethylene)-2,3-dihydrobenzo[b]furan-2-ones 8-10 and 3-(3,5-dimethylpyrrol-2-ylmethylene)-2,3-dihydrobenzo[b]furan-2-one 11, analogues of SU-5416, as potential inhibitors of angiogenesis, are reported. Compounds 8 and 11 were prepared by a Knoevenagel reaction starting from 2-hydroxyphenylacetic acid 2 and 4-formylimidazole 5 or 2-formyl-3,5-dimethylpyrrole 7, followed by acid-catalysed cyclodehydration. For compounds 9 and 10, an alternative method was used; it consisted in carrying out the Knoevenagel reaction with the 2,3-dihydrobenzo[b]furan-2-ones 3 and 4. The antiangiogenic activity of these compounds was evaluated in the three-dimensional in vitro rat aortic rings test at 1 μM. At this concentration, compound 11 induced a decrease of angiogenesis comparable to that observed with SU-5416; the vascular density index at 1 μM of 11 and SU-5416 were 30±10 and 22±4% of control, respectively.     

Inhibition of human chymase by 2-amino-3,1-benzoxazin-4-ones

A series of 2-sec.amino-4H-3,1-benzoxazin-4-ones was evaluated as acyl-enzyme inhibitors of human recombinant chymase. The compounds were also assayed for inhibition of human cathepsin G, bovine chymotrypsin, and human leukocyte elastase. Introduction of an aromatic moiety into the 2-substituent resulted in strong inhibition of chymase, cathepsin G, and chymotrypsin. Extension of the N(Me)CH2Ph substituent by one methylene unit was unfavourable to inhibit these proteases. Towards chymase, 2-(N-benzyl-N-methylamino)-4H-3,1-benzoxazin-4-one (32) and 2-(N-benzyl-N-methylamino)-6-methyl-4H-3,1-benzoxazin-4-one (33) were found to exhibit Ki values of 11 and 17 nM, respectively, and form stable acyl-enzymes with half-lives of 53 and 25 min, respectively. Benzoxazinone 33 also inhibited the human chymase-catalyzed formation of angiotensin 11 from angiotensin I.     

4-alkoxy-3-arylfuran-2(5H)-ones as inhibitors of tyrosyl-tRNA synthetase: synthesis, molecular docking and antibacterial evaluation

A series of novel 4-alkoxy-3-arylfuran-2(5H)-ones as tyrosyl-tRNA synthetase inhibitors were synthesized. Of these compounds, 3-(4-hydroxyphenyl)-4-(2-morpholinoethoxy)furan-2(5H)-one (27) was the most potent. The binding model and structure-activity relationship indicate that replacement of morpholine-ring in the side chain of 27 with a substituent containing more hydrophilic groups would be more suitable for further modification. Antibacterial assay revealed that the synthetic compounds are effective against growth of Gram-positive organisms, and 27 is the most potent agent against Staphylococcus aureus ATCC 25923 with MIC(50) value of 0.23 μg/mL.     

Effect of C-ring modifications in benzo[c]quinolizin-3-ones, new selective inhibitors of human 5 alpha-reductase 1.

The synthesis and the inhibition potency of octahydro- and decahydrobenzo[c]quinolizin-3-one derivatives 3--7, as new non-steroidal selective inhibitors of human enzyme 5 alpha-reductase type 1, are reported. These compounds differ from the recently reported benzo[c]quinolizin-3-one inhibitors 2 by the presence of a fully or partially saturated C-ring. Compounds 3 and 4, with a double bond in the C-ring, were prepared by sequential rearrangement-annulation of isoxazolines 19 and 20. C-ring saturated compounds 5--7 were prepared by the Lewis acid-promoted Mannich-Michael tandem reaction of Danishefsky diene with the appropriate N-t-Boc iminium ion. Inhibition experiments were carried out on 5 alpha R-1 and 5 alpha R-2 expressed by CHO cells. Among the prepared compounds, octahydrobenzo[c]quinolizin-3-one 3, with a double bond at the position 6a--10a, was a potent and selective inhibitor of human 5 alpha R-1 (IC(50)=58 nM). The introduction of a tert-butylcarboxyamide at the position 8 (compound 4) was deleterious for the inhibition activity. The lack of the double bond in the C-ring reduced strongly the inhibition activity of compounds 5--7. The extended planarity of the most potent benzo[c]quinolizin-3-ones as well as favorable interactions of the C-ring unsaturation with the enzyme active site could account for the inhibition activity of these compounds.     

The altered specificity of cortisone reductase with certain retroandrostan-3-one substrates.

The retro steroids 17beta-hydroxy-5beta,9beta,10alpha-androstan-3-one and 5beta,9beta,10alpha-androstane-3,17-dione were good substrates for cortisone reductase in the presence of NADH, and the products corresponded to the respective 3beta-hydroxy compounds, in which the 3beta-hydroxyl group is axial and the absolute configuration is 3S. The analogous natural steroids 17beta-hydroxy-5beta,9alpha,10beta-androstan-3-one and 5beta,9alpha,10beta-androstane-3,17-dione were very poor substrates, and gave the corresponding 3alpha(equatorial,3R)-hydroxy compounds, and, in the latter case, also an appreciable amount of 3beta(axial, 3S)-hydroxy-5beta,9alpha,10beta-androstan-17-one. The natural steroids 17beta-hydroxy-5alpha,9alpha,10beta-androstan-3-one and 5alpha,9alpha,10beta-androstane-3,17-dione were better substrates than the retro steroid 17beta-hydroxy-5alpha,9beta,10alpha-androstan-3-one, but were not such good substrates as the retro steroids 17beta-hydroxy-5beta,9beta,10alpha-androstan-3-one and 5beta,9beta,10alpha-androstane-3,17-dione. Unlike these retro steroid 5beta,9beta,10alpha-androstan-3-ones, the natural steroids 17beta-hydroxy-5alpha,9alpha,10beta-androstan-3-one and 5alpha,9alpha,10beta-androstane-3,17-dione gave the corresponding 3alpha(axial,3R)-hydroxy compounds. The retro steroid 17beta-hydroxy-5alpha,9beta,10alpha-androstan-3-one was not a good substrate, and the product of reaction corresponded to the 3alpha(axial,3R)-hydroxy compound. The nature of substrate recognition by this enzyme is discussed in the light of these structure-activity relationships.     

Synthesis and antihypertensive activity of novel 3-benzyl-2-substituted-3H-[1,2,4]triazolo[5,1-b]quinazolin-9-ones

A series of 3-benzyl-2-substituted-3H-[1,2,4]triazolo[5,1-b]quinazolin-9-ones have been synthesized by the cyclocondensation of 3-amino-2-benzylamino-3H-quinazolin-4-one with a variety of one-carbon donors. The starting material 3-amino-2-benzylamino-3H-quinazolin-4-one was synthesized from methyl anthranilate by a novel innovative route. The title compounds were evaluated for their in vivo antihypertensive activity using spontaneously hypertensive rats (SHR). While all the test compounds exhibited significant antihypertensive activity, 3-benzyl-2-methyl-3H-[1,2,4]triazolo[5,1-b] quinazolin-9-one exhibited antihypertensive activity more than the reference standard prazocin.     

Molecular hybridization of bioactives: Synthesis and antitubercular evaluation of novel dibenzofuran embodied homoisoflavonoids via Baylis–Hillman reaction

A novel series of natural product like dibenzofuran embodied homoisoflavonoids [(E)-3-(dibenzo[b,d]furan-2-ylmethylene)chroman-4-ones] designed by molecular hybridization were synthesized in very good yields via a sequence of reactions involving base catalyzed Baylis–Hillmann (BH) reaction of 2-dibenzofuran carboxaldehyde and methyl acrylate; bromination of BH adduct; condensation of resulted allylic bromide with substituted phenols or 2-dibenzofuranol followed by cyclization. Among the all 11 new compounds screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB), (E)-3-(dibenzo[b,d]furan-2-ylmethylene)-6-fluorochroman-4-one (7f) and (E)-3-(dibenzo[b,d] furan-2-ylmethylene)-6-fluorochroman-4-one (7g) were found to be active with MIC 12.5 μg/mL.     

Synthesis of new bioactive venlafaxine analogs: novel thiazolidin-4-ones as antimicrobials

A one-pot, three-component, microwave irradiated and conventional solution-phase synthesis of bioactive venlafaxine analogs such as 2,3-disubstituted-1,3-thiazolidin-4-ones 3a-j under mild conditions and their characterization are reported. The novel thiazolidin-4-ones, 3-(2-(1-hydroxycyclohexyl)-2-(4-methoxyphenyl)ethyl)-2-phenyl-thiazolidin-4-one 3a, 2-(2,6-difluorophenyl)-3-(2-(1-hydroxycyclohexyl)-2-(4-methoxyphenyl)ethyl)thiazolidin-4-one 3c, and 2-(furan-2-yl)-3-(2-(1-hydroxycyclohexyl)-2-(4-methoxyphenyl)ethyl)thiazolidin-4-one 3i, were characterized by the single crystal X-ray diffraction method. The cyclohexane ring of all the three molecules is in chair conformation. All the synthesized compounds were screened for their efficacy as antimicrobials in vitro by the disk diffusion and microdilution method against pathogenic strains such as Bacillus subtilis, Escherichia coli, Pseudomonas fluorescens, Xanthomonas campestris pvs, Xanthomonas oryzae, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Trichoderma species, and Fusarium monaliforme species. Among these compounds 3c, 3j, 3g, 3d, and 3e showed potent antimicrobial activity, when compared to standard drugs.     

Synthesis and pharmacological investigation of novel 4-benzyl-1-substituted-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-ones as new class of H1-antihistaminic agents

A series of novel 1-substituted-4-benzyl-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-ones were synthesized by the cyclization of 2-hydrazino-3-benzyl-3H-quinazolin-4-one with various one-carbon donors. The starting material 2-hydrazino-3-benzyl-3H-quinazolin-4-one was synthesized from benzylamine by a new innovative route. When tested for their in vivo H1 -antihistaminic activity on guinea pigs, all the test compounds protected the animals from histamine induced bronchospasm significantly. The compound 1-methyl-4-benzyl-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-one (II) emerged as the most active compound of the series and it is more potent (percent protection 76%) when compared to the reference standard chlorpheniramine maleate (percent protection 71%). Compound II showed negligible sedation (7%) when compared to chlorpheniramine maleate (30%). Hence it could serve as prototype molecule for further development as a new class of H1 -antihistamines.     

A "cephalosporin-like" cyclic depsipeptide: synthesis and reaction with beta-lactam-recognizing enzymes

The cyclic depsipeptide 8-carboxy-3-phenylacetamido-3,4-dihydro-2H-1-benzopyran-2-one, a cyclic analog of aryl phenaceturates with structural similarity to cephalosporins, has been synthesized as a potential substrate/inhibitor of B-lactam-recognizing enzymes. It was found to be a tight-binding, poor substrate of class A beta-lactamases and an irreversible inhibitor of several DD-peptidases.     

Synthesis of substituted 5[H]phenanthridin-6-ones as potent poly(ADP-ribose)polymerase-1 (PARP1) inhibitors

1-, 2-, 3-, 4-, 8-, or 10-Substituted 5(H)phenanthridin-6-ones were synthesized and found to be potent PARP1 inhibitors. Among the 28 compounds prepared, some showed not only low IC₅₀ values (compound 1b, 10 nM) but also desirable water solubility characteristics. These properties, which are superior to the common PARP1 inhibitors such as benzamides and isoquinolin-1-ones, are essential for potential therapeutic usage. The variety of compounds allows SAR analysis of favored substituents and substituted positions on 5(H)phenanthridin-6-one ring.     

Antifungal secondary metabolites from endophytic Verticillium sp.

Endophytes were isolated from roots of wild Rehmannia glutinosa to screen the strains with antifungal metabolites. A strain identified as Verticillium sp. was selected for chemical and biological investigations because of the strong antifungal activity of the crude extract against Pyricularia oryzae P-2b. Chemical investigations of culture broth afforded three compounds: 2,6-dihydroxy-2-methyl-7-(prop-1E-enyl)-1-benzofuran-3(2H)-one, massariphenone and ergosterol peroxide. The metabolites were isolated by silica gel and Sephadex LH-20, 2,6-dihydroxy-2-methyl-7-(prop-1E-enyl)-1-benzofuran-3(2H)-one was reported for the first time and the chemical structure was established following the analysis of NMR, UV, IR, MS data. 2,6-Dihydroxy-2-methyl-7-(prop-1E-enyl)-1-benzofuran-3(2H)-one and ergosterol peroxide displayed clear inhibition of the growth of three pathogens as well as Verticillium sp.     

An improved synthesis of an umbelliferyl 5-thioxylopyranoside, precursor of the antithrombotic drug Iliparcil.

4-Ethyl-2-oxo-2H-1-benzopyran-7-yl 2,3,4-tri-O-acetyl-5-thio-beta-D-xylopyranoside, a synthetic intermediate of the orally active antithrombotic compound Iliparcil, has been prepared in 44-47% isolated yield. Different conditions were used for the glycosylation of 4-ethyl-2H-7-hydroxy-1-benzopyran-2-one 6 applying 2,3,4-tri-O-acetyl-5-thio-D-xylopyranosyl bromide (2), the analogous beta-chloride 3 or the alpha-trichloroacetimidate 5 as donors. With halides 2 and 3, the reaction was carried out in the presence of ZnO-ZnCl2 or ZnO alone. Both promoters are cheap, safe and therefore compatible with large-scale industrial processes.