Studies on the structure-fluorescence relationships of chromatin-bound 9-amino acridine derivatives

Microscopic assessment and microphotometric measurement of the fluorescence intensity of human metaphase chromosomes stained with 24 9-amino acridine derivatives differing in chemical structure, led to the following conclusions:

1. 1. With the -OCH₃ group as a substituted radical in the acridine core, the fluorescent intensity of the stain bonded with chromosomes increases. The best fluorochromes contain this group in position 5 or 7. The fluorescent intensity increases in the presence of a halogen atom in position 3, or with a second -OCH₃ group in position 4. These observations suggest that the rise in fluorescent intensity is caused by substitutes that increase the density of the π electrons in acridine rings.

2. 2. Weak fluorescent intensity is displayed by 9-amino acridine derivatives containing less than 3 -CH₂ groups in the side chain in position 9.

3. 3. Alkylizing the guanine of chromosomal DNA by acridine derivatives is not an indispensible condition for achieving well differentiated fluorescence of metaphase chromosomes.

     

Insight into dihalogenation of E-ring of podophyllotoxins,and their acyloxyation derivatives at the C4 position as insecticidal agents

Unexpected sequential E-ring dihalogenation of podophyllotoxin analogues is reported. It demonstrated that a chlorine/bromine atom was prior introduced at the C2′ position of podophyllotoxin, and the corresponding free rotation of E-ring around the C1–C1′ bond of 2′-chloro or 2′-bromopodophyllotoxin was restricted. When 2′-chloro or 2′-bromopodophyllotoxin reacted with N-chlorosuccinimide (NCS), the chlorine atom was regioselectively introduced at their C6′ position on the E-ring. Whereas 2′-chloro or 2′-bromopodophyllotoxin reacted with NBS, the bromine atom was regioselectively introduced at their C5 position on the B-ring. When 2′-chloropodophyllotoxin reacted with different carboxylic acids in the presence of BF₃·Et₂O, the steric effect of its E-ring for stereoselective synthesis of 4β-acyloxy-2′-chloropodophyllotoxin derivatives was observed. The insecticidal activity of 2′(2′,6′)-(di)halogen-substituted podophyllotoxin derivatives were evaluated with Mythimna separata Walker.     

Analysis of prostaglandins by electron-capture gas chromatography. I. Thermal decomposition of heptafluorobutyrate methyl esters of F1α and F2α

Triheptafluorobutyrate methyl ester (THFB-Met) derivatives are easily prepared from prostaglandins F_1α and F_2α by successive methylation and heptafluorobutyrylation. The derivatives are reasonably stable during storage, are volatile, and can be detected in the picogram range by electron-capture gas chromatography. Both derivatives exhibit peak broadening or multiple peak formation during gas chromatography at 190°–210°C. Decomposition is independent of the nature of the stationary phase and can be increased by prior heating. Studies with other derivatives suggest that thermal decomposition of the THFB-Met derivatives occuring during gas chromatography involves loss of a heptafluorobutyrate group from the allylic position 15 of the prostaglandins.     

Highly stereoselective synthesis of C-vinyl furanosides through acid-catalyzed S(N)2 inversion at the C-3 position of 1,2-dideoxy-hept-1-enitols

A highly stereoselective synthesis of C-vinyl furanosides through the S_N2 inversion at the C-3 position of the 1,2-dideoxy-hept-1-enitols is disclosed. Treatment of the 1,2-dideoxy-hept-1-enitols with diphenylammonium trifluoromethanesulfonate as the acid catalyst produced the C-vinyl furanosides (3,6-anhydro-1,2-dideoxy-hept-1-enitol derivatives) via a subsequent S_N2 intramolecular debenzyloxyation-cycloetherification reaction at the C-3 position.     

Cytokinins: Synthesis of 2-, 8-, and 2,8-substituted 6-(3-methyl-2-butenylamino)purines and their relative activities in promoting cell growth

We have synthesized 2- and 8-monosubstituted and 2,8-disubstituted derivatives of the cytokinin 6-(3-methyl-2-butenylamino)purine (N⁶-isopentenyladenine) and have shown the dependence of growth-promoting activity in the tobacco bioassay upon the position, number, and type of substituent. The representative substituent groups were MeS, Me, MeSO₂, C₆H₅CH₂S, HS and Cl. The 8-methyl derivative was exceptional in being more active than the unsubstituted parent compound. In general, substitution in the 8-position decreases activity less than substitution in the 2-position, with the exception of the electron-attracting methylsulfonyl. Substitution in both the 2- and 8-positions lowers the activity more than substitution at either single position on the adenine nucleus, with the exception of the 2,8-dimethyl derivative. The chloro and methylthio derivatives show activity in the same range as the methyl derivatives, and the mercapto compounds, which exist mainly as CS tautomers, show somewhat less activity than the corresponding methylthio compounds. Bulky (C₆H₅CH₂S and MeSO₂) and strongly electron-attracting (MeSO₂) substituents cause relatively great reduction in cytokinin activity.     

Inhibition of Mouse Blastocyst Hatching by Subsite-Specific Trypsin Inhibitors,Peptidyl Argininals1

To explore the substrate or subsite specificity of a mouse hatching enzyme, effects of leupeptin [acetyl(P₄)-Leu(P₃)-Leu(P₂)-argininal(P₁)] and its analogs (peptidyl argininals) on mouse blastocyst hatching were investigated. The compounds containing benzyloxycarbonyl group (Z) in the P₄ position inhibited the hatching more strongly than those containing acetyl group or unprotected N-terminal amino acid. Among five Z-Leu-P₂-argininals, a derivative containing a P₂ Ser residue was the most potent inhibitor, and the derivatives containing Leu, Thr, Pro, and Gly in the P₂ position followed in this order. Then, we synthesized four Z-P₃-Ser-argininals and tested their effects on hatching. The result indicated that the compound with Phe residue in the P₃ position was the strongest inhibitor, and the Leu-, Pro-, and Ala-containing derivatives were ranked in this order. Thus, among Z-dipeptidyl-argininals tested, Z-Phe-Ser-argininal most potently inhibited the mouse embryonic hatching, suggesting the preference of the mouse hatching enzyme for Phe(P₃)-Ser(P₂)-Arg(P₁) sequence as a substrate.     

Novel Modification of 5-Formyluracil by Cysteine Derivatives in Aqueous Solution‡

Abstract

Reactivities of 5-formyl-2′-deoxyuridine (fdU) and its 5′-monophosphate (fdUMP) to amino acids, amines and thiol compounds in neutral aqueous solution have been studied to elucidate the postmodification of the 5-formyluracil (fU) moiety in cells. fdU and fdUMP specifically reacted with cysteine and its analogs to form thiazolidine derivatives. The reaction involved condensation of the formyl group of fU with both α-NH₂ (or NH₂ at the equevalent position) and SH groups of cysteine derivatives.

     

Antibacterial effect of some substituted tricyclic quinazolines and their synthetic precursors

Eleven substituted tricyclic quinazolines and their synthetic precursors were tested for antibacterial effects. 3-Chloromethylcarbonyl-2-methylquinazolin-4-thione and 5-phenyl-2,3-dihydro-1,2,4-triazolo[4,3-c]quinazolin-3-one had the highest antibacterial effect againstBacillus subtilis, the MIC values being 50 mg/L. Two tested derivatives were more active againstPseudomonas aeruginosa than ampicillin, the IC₅₀ values being 80 and 100 mg/L. The most effective derivatives contained in the structure generally pharmacologically active chromophores—methyl group in position 2 and a chloromethyl configuration on the carbonyl group in position 3.     

Synthesis and structure–activity relationship of p-carborane-based non-secosteroidal vitamin D analogs

1α,25-Dihydroxyvitamin D₃ [1α,25(OH)₂D₃: 1] is a specific modulator of nuclear vitamin D receptor (VDR), and novel vitamin D analogs are therapeutic candidates for multiple clinical applications. We recently developed non-secosteroidal VDR agonists bearing a p-carborane cage (a carbon-containing boron cluster) as a hydrophobic core structure. These carborane derivatives are structurally quite different from classical secosteroidal vitamin D analogs. Here, we report systematic synthesis and activity evaluation of carborane-based non-secosteroidal vitamin D analogs. The structure–activity relationships of carborane derivatives are different from those of secosteroidal vitamin D derivatives, and in particular, the length and the substituent position of the dihydroxylated side chain are rather flexible in carborane derivatives. The structure–activity relationships presented here should be helpful in development of non-secosteroidal vitamin D analogs for clinical applications.     

Design, synthesis and SAR of novel ethylenediamine and phenylenediamine derivatives as factor Xa inhibitors

We previously reported on a series of cyclohexanediamine derivatives as highly potent factor Xa inhibitors. Herein, we describe the modification of the spacer moiety to discover an alternative scaffold. Ethylenediamine derivatives possessing a substituent at the C1 position in S configuration and phenylenediamine derivatives possessing a substituent at the C5 position demonstrated moderate to strong anti-fXa activity. Further SAR studies led to the identification of compound 30h which showed both good in vitro activity (fXa IC₅₀ = 2.2 nM, PTCT2 = 3.9 μM) and in vivo antithrombotic efficacy.     

Looking for high energy density compounds among polynitraminepurines

A series of purine derivatives with nitramine groups are calculated by using density functional theory (DFT). The molecular theory density, heats of formation, bond dissociation energies and detonation performance are investigated at DFT-B3LYP/6-311G** level. The isodesmic reaction method is employed to calculate the HOFs of the energies obtained from electronic structure calculations. Results show that the position of nitramine groups can influence the values of HOFs. The bond dissociation energies and the impact sensitivity are analyzed to investigate the thermal stability of the purine derivatives. The calculated bond dissociation energies of ring-NHNO₂ and NH-NO₂ bond show that the NH-NO₂ bond should be the trigger bond in pyrolysis processes. The H₅₀ of most compounds are larger than that of CL-20 and RDX.     

Can one predict protein stability? An attempt to do so for residue 133 of T4 lysozyme using a combination of free energy derivatives,PROFEC, and free energy perturbation methods

Free energy derivatives, pictorial representation of free energy changes (PROFEC) and free energy perturbation methods were employed to suggest the modifications that may improve the stability of a mutant T4 lysozyme with a S-2-amino-3-cyclopentylpropanoic acid residue (Cpe) at position 133. The free energy derivatives and PROFEC methods were used to locate promising sites where modifications may be introduced. The effects of several candidate modifications on the enzyme's stability were analyzed by the free energy perturbation method. We found that this scheme is able to effectively suggest modifications that may increase the enzyme's stability. The modifications investigated are the introduction of a methyl, a tert-butyl or a trifluoromethyl group at the C_ϵ2 position and a cyclopropyl group between the C_δ2 and C_ϵ2 position on the cyclopentyl ring. The stereochemistry of the introduced groups (in the α or β configurations) was studied. Our calculations predict that the introduction of a methyl group in the α configuration or a cyclopropyl group in the β configuration will increase the stability of the enzyme; the introduction of the two groups in the other configurations and the other modifications will decrease the stability of the enzyme. The results indicate that packing interactions can strongly influence the stability of the enzyme. Proteins 32:438–458, 1998. © 1998 Wiley-Liss, Inc.     

Inhibition of monoamine oxidase by 3,4-dihydro-2(1H)-quinolinone derivatives

In the present study, a series of 3,4-dihydro-2(1H)-quinolinone derivatives were synthesized and evaluated as inhibitors of recombinant human monoamine oxidase (MAO) A and B. The 3,4-dihydro-2(1H)-quinolinone derivatives are structurally related to a series of coumarin (1-benzopyran-2-one) derivatives which have been reported to act as MAO-B inhibitors. The results document that the quinolinones are highly potent and selective MAO-B inhibitors with most homologues exhibiting IC₅₀ values in the nanomolar range. The most potent MAO-B inhibitor, 7-(3-bromobenzyloxy)-3,4-dihydro-2(1H)-quinolinone, exhibits an IC₅₀ value of 2.9 nM with a 2750-fold selectivity for MAO-B over the MAO-A isoform. An analysis of the structure–activity relationships for MAO-B inhibition shows that substitution on the C7 position of the 3,4-dihydro-2(1H)-quinolinone scaffold leads to significantly more potent inhibition compared to substitution on C6. In this regard, a benzyloxy substituent on C7 is more favourable than phenylethoxy and phenylpropoxy substitution on this position. It may be concluded that C7-substituted 3,4-dihydro-2(1H)-quinolinones are promising leads for the therapy of Parkinson’s disease.     

Design,synthesis, in vitro antiproliferative activity and apoptosis-inducing studies of 1-(3′,4′,5′-trimethoxyphenyl)-3-(2′-alkoxycarbonylindolyl)-2-propen-1-one derivatives obtained by a molecular hybridisation approach

Inhibition of microtubule function using tubulin targeting agents has received growing attention in the last several decades. The indole scaffold has been recognized as an important scaffold in the design of novel compounds acting as antimitotic agents. Indole-based chalcones, in which one of the aryl rings was replaced by an indole, have been explored in the last few years for their anticancer potential in different cancer cell lines. Eighteen novel (3′,4′,5′-trimethoxyphenyl)-indolyl-propenone derivatives with general structure 9 were synthesized and evaluated for their antiproliferative activity against a panel of four different human cancer cell lines. The highest IC₅₀ values were obtained against the human promyelocytic leukemia HL-60 cell line. This series of chalcone derivatives was characterized by the presence of a 2-alkoxycarbonyl indole ring as the second aryl system attached at the carbonyl of the 3-position of the 1-(3′,4′,5′-trimethoxyphenyl)-2-propen-1-one framework. The structure–activity relationship (SAR) of the indole-based chalcone derivatives was investigated by varying the position of the methoxy group, by the introduction of different substituents (hydrogen, methyl, ethyl or benzyl) at the N-1 position and by the activity differences between methoxycarbonyl and ethoxycarbonyl moieties at the 2-position of the indole nucleus. The antiproliferative activity data of the novel synthesized compounds revealed that generally N-substituted indole analogues exhibited considerably reduced potency as compared with their parent N-unsubstituted counterparts, demonstrating that the presence of a hydrogen on the indole nitrogen plays a decisive role in increasing antiproliferative activity. The results also revealed that the position of the methoxy group on the indole ring is a critical determinant of biological activity. Among the synthesized derivatives, compound 9e, containing the 2-methoxycarbonyl-6-methoxy-N-1H-indole moiety exhibited the highest antiproliferative activity, with IC₅₀ values of 0.37, 0.16 and 0.17?μM against HeLa, HT29 and MCF-7 cancer cell lines, respectively, and with considerably lower activity against HL-60 cells (IC₅₀: 18?μM). This derivative also displayed cytotoxic properties (IC₅₀ values ～1?μM) in the human myeloid leukemia U-937 cell line overexpressing human Bcl-2 (U-937/Bcl-2) via cell cycle progression arrest at the G₂-M phase and induction of apoptosis. The results obtained also demonstrated that the antiproliferative activity of this molecule is related to inhibition of tubulin polymerisation. The presence of a methoxy group at the C5- or C6-position of the indole nucleus, as well as the absence of substituents at the N-1-indole position, contributed to the optimal activity of the indole-propenone-3′,4′,5′-trimethoxyphenyl scaffold.     

Design,synthesis and biological evaluation of potential antibacterial butyrolactones

Novel butyrolactone analogues were designed and synthesized based on the known lichen antibacterial compounds, lichesterinic acids (B-10 and B-11), by substituting different functional groups on the butyrolactone ring trying to enhance its activity. All synthesized butyrolactone analogues were evaluated for their in vitro antibacterial activity against Streptococcus gordonii. Among the derivatives, B-12 and B-13 had the lowest MIC of 9.38 μg/mL where they have shown to be stronger bactericidals, by 2–3 times, than the reference antibiotic, doxycycline. These two compounds were then checked for their cytotoxicity against human gingival epithelial cell lines, Ca9–22, and macrophages, THP-1, by MTT and LDH assays which confirmed their safety against the tested cell lines. A preliminary study of the structure–activity relationships unveiled that the functional groups at the C₄ position had an important influence on the antibacterial activity. An optimum length of the alkyl chain at the C₅ position registered the best antibacterial inhibitory activity however as its length increased the bactericidal effect increased as well. This efficiency was attained by a carboxyl group substitution at the C₄ position indicating the important dual role contributed by these two substituents which might be involved in their mechanism of action.     

Synthesis,anticancer and antioxidant activities of some novel N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives

A series of N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives were synthesized by treating N-(benzoxazol-2-yl)hydrazinecarboxamide with different isatin derivatives. The newly synthesized compounds were characterized on the basis of spectral analyses. All the synthesized derivatives (Va-l) were screened for anticancer and antioxidant activities. The results showed the anticancer activity of test compounds against HeLa, IMR-32 and MCF-7 cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. All the synthetic compounds produced a dose-dependant inhibition of growth of the cells. The IC₅₀ values of some compounds were comparable with standard anticancer agent, cisplatin. All the title compounds effectively scavenged the free radical, α,α-diphenyl-β-picryl hydrazyl. The test compounds having substitution with different halides (electron withdrawing groups) at C5 position showed more potent anticancer and antioxidant activities than those at C7 position. These results indicate that C5-substituted derivatives may be useful for developing antioxidant agents that play a protective role in many pathological conditions such as cancer, diabetes and so on.     

Click-tailed benzenesulfonamides as potent bacterial carbonic anhydrase inhibitors for targeting Mycobacterium tuberculosis and Vibrio cholerae

A series of 1,2,3-triazole-bearing benzenesulfonamides was assessed for the inhibition of carbonic anhydrases (CA, EC 4.2.1.1) from bacteria Vibrio cholerae (VchCAα and VchCAβ) and Mycobacterium tuberculosis (β-mtCA3). Growing resistance phenomena against existing antimicrobial drugs are globally spreading and highlight a urgent need of agents endowed with alternative mechanisms of action. Two global WHO strategies aim to reduce cholera deaths by 90% and eradicate the tuberculosis epidemic by 2030. The derivatives here reported represent interesting leads towards the optimization of new antibiotic agents showing excellent inhibitory efficiency and selectivity for the target CAs over the human (h) off-target isoform hCA I. In detail, the first subset of derivatives potently inhibits VchCAα in a low nanomolar range (K_Is between 0.72 and 22.6 nM). Compounds of a second subset, differing from the first one for the position of the spacer between benzenesulfonamide and triazole, preferentially inhibit VchCAβ (K_Is in the range 54.8–102.4 nM) and β-mtCA3 (K_Is in the range 28.2–192.5 nM) even more than the clinically used AAZ, used as the standard.     

Uncoupling of the substrate monooxygenation and reduced pyridine nucleotide oxidation activities of salicylate hydroxylase by flavins

The NAD(P)H oxidation and substrate monooxygenation activities of Pseudomonas cepacia salicylate hydroxylase can be uncoupled by added flavins. The uncoupling is postulated to result from a reducing equivalent exchange between the hydroxylase-bound FADH₂ and the added flavins, leading to the reduction of the latter species and the regeneration of oxidized holoenzyme without hydroxylating the salicylate substrate. When exogenous FMN was added, the salicylate hydroxylase-catalyzed NAD(P)H oxidation could be coupled to the bacterial bioluminescence reaction, which is specific for fully reduced FMN as a substrate. The quantum yield of the coupled bioluminescence, based on the amount of NADH oxidized independently of salicylate monooxygenation, was determined to be 0.14 correlating closely with the known quantum yield of about 0.17 for reduced FMN in the luciferase-catalyzed bioluminescence reaction. A series of flavin derivatives were tested for their effects on the uncoupling of NAD(P)H oxidation and substrate monooxygenation activities of salicylate hydroxylase. Results indicated that the efficiency for interactions between the bound FADH₂ and free flavins was sensitive to the position of structural modification, size, and charge of the added flavin species, suggesting that the bound FADH₂ was partially exposed to aqueous medium under conditions of actual catalysis.     

Synthesis of GN8 derivatives and evaluation of their antiprion activity in TSE-infected cells

A series of GN8 derivatives were synthesized from various diamines, carboxylic acid derivatives, and nitrogen nucleophiles, and their antiprion activity was tested in TSE-infected mouse neuronal cells. We found that two ethylenediamine units, hydrophobic substituents on the nitrogen atoms, and the diphenylmethane scaffold were essential structural features responsible for the activity. Seven derivatives bearing substituents at the benzylic position exhibited an improved antiprion activity with the IC₅₀ values of 0.51-0.83 μM. Conformational analysis of model compounds suggested that the introduction of the substituent at the benzylic position restricted the conformational variability of the diphenylmethane unit.     

Novel rhodanine derivatives are selective algicides against <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

In this study, a series of rhodanine derivatives containing various substituents was synthesized and tested for in vitro algicidal activity. Among the tested substituent groups, phenyl substituents with halogen groups showed good inhibitory potency. Furthermore, the compound with chlorine at the C2 position of the phenyl ring exhibited a higher algicidal effect than the compound with chlorine at the C3 position of the phenyl ring. Among the various rhodanine derivatives tested, 5-(2,4-dichlorobenzylidene)- rhodanine (compound 20) was the most potent inhibitor against M. aeruginosa with a lethal concentration 50 (LC₅₀) value of 0.65 μM and Selenastrum capricornutum with an LC₅₀ value of 0.82 μM. To verify the feasibility of their use in ecosystems, 25 h of acute ecotoxicity tests were carried out for three derivatives against Danio rerio and Daphnia magna. No mortality was observed in groups exposed to 2.0 μM of compound 20 after 100 h of exposure. Moreover, a survival rate of 100% was observed in D. magna exposed to 2 μM of compound 20 for 100 h. Overall, the results show that rhodanine derivatives are a possible method for controlling and inhibiting harmful algal blooms.