Synthesis of novel 7-substituted pyrido[2′,3′:4,5]furo[3,2-d]pyrimidin-4-amines and their N-aryl analogues and evaluation of their inhibitory activity against Ser/Thr kinases

The efficient synthesis of 7-substituted pyrido[2′,3′:4,5]furo[3,2-d]pyrimidin-4-amines and their N-aryl analogues is described. 3,5-Dibromopyridine was converted into 3-amino-6-bromofuro[3,2-b]pyridine-2-carbonitrile intermediate which was formylated with DMFDMA. Functionalization at position 7 of the tricyclic scaffold was accomplished, before or after cyclisation step, by palladium-catalyzed Suzuki–Miyaura cross-coupling while the pyrimidin-4-amines and N-aryl counterparts were synthesized by microwave-assisted formamide degradation and Dimroth rearrangement, respectively. The final products were evaluated for their potent inhibition of a series of five Ser/Thr kinases (CDK5/p25, CK1δ/ε, CLK1, DYRK1A, GSK3α/β). Compound 35 showed the best inhibitory activity with an IC₅₀ value of 49 nM and proved to be specific to CLK1 among the panel of tested kinases.     

Synthesis and activity evaluation of the cyclic dipeptides arylidene N-alkoxydiketopiperazines

A series of arylidene N-alkoxydiketopiperazines was designed and stereoselectively synthesized via oxime-ether formation and intramolecular acylation. Possible cyclization and acid-catalyzed rearrangement-fragmentation mechanisms were discussed. The crystal structure of the novel diketopiperazine further confirmed the rearrangement mechanism. Most compounds exhibited antitumor activity. Several compounds were more potent against caspase-3. Specifically, compounds 6e, 6g, and 6f inhibited caspase-3 at IC₅₀ values lying within the low micromolar range and demonstrated good selectivity. The binding modes of alkoxydiketopiperazines in the active center of caspase-3 were also discussed based on the molecular docking results.     

Comparison of mutagenicity and chemical properties of N-methyl-N′-alkyl-N-nitrosoureas

Thed mutagenic activities of 11 N-methyl-N′-alkyl-N-nitrosoureas were tested on Samonellatyphimurium TA1535 and compared with chemical properties (alkylating activity and decompostion rate). In their relative mutagenicities the N-nitrosoureas that had a cyclic N′-alkyl group showed far more mutagenic activity than those having a chain N′-alkyl group. M(1-A)NU and M(2-A)NU, which had the most bulky N′-alkyl group in this series, exhibited lethal effects at high concentrations. The mutagenicity showed a small positive correlation with decomposition rates but not with alkylating activities on 4-(p-nitrobenzyl_prridine. The highest mutagenicity in this series was observed in N-methyl-N′-cyclobutyl-N-nitrosourea.These results suggest that, in this series of N-methyl-M′-alkyl-N-nitrosoureas, structural differences in the N′-alkyl groups had great significance in mutagenicity.     

Pseudo-halogen sugar derivatives: Synthesis and hofmann-rearrangement reactions; 6-O-[2-(N,N-dichlorocarbamoyl)-ethyl]-1,2:3,4-di-O-isopropylidene-α-d-galactopyranose

6-O-[2-(N,N-Dichlorocarbamoyl)ethyl]-1,2:3,4-di- O-isopropylidene-α-d-galactopyranose, a highly reactive pseudo-halogen, was conveniently prepared in 97% yield by addition of sodium hypochlorite to an aqueous acidic (pH <2) solution of 6-O-(2-carbamoylethyl)-1,2:3,4-di-O-isopropylidene-α-d-galactopyranose. Mild, reductive dechlorination or alkaline hydrolysis readily converted the nonpolar N,N-di-chloroamide sugar derivative into the corresponding water-soluble N-monochloroamide form. Hofmann rearrangement of the N-chloroamide group provides a synthetic route to novel binary sugar-derivatives having carbamoyl, ureylene, and allophanoyl linkages. Structural proof for the pseudo-halogens and their Hofmann-rearrangement products was obtained from i.r., ¹H-n.m.r., mass-spectral, and chemical data.     

Two series of copper(II) complexes derived from various 2-urethanylpyridine N-oxides (2-ethoxycarbonylaminopyridine N-oxides)

A series of new aromatic N-oxide ligands have been prepared by converting the 2-amino group of 2-aminopyridine N-oxide, 2-aminopicoline N-oxides and 2-amino-4,6-lutidine N-oxide into a urethane. Two series of copper(II) complexes have been prepared and characterized by their infrared, electronic and ESR spectra along with other physicochemical methods. One series has the stoichiometry [Cu(UOH)₄](ClO₄)₂ and involves monodentate coordination via the N-oxide oxygen and the other series is prepared from copper(II) acetate and has the stoichiometry [Cu(UO)₂]. In this latter series coordination occurs via the _N-oxide oxygen and the deprotonated amino function.     

Derivatives of aryl amines containing the cytotoxic 1,4-dioxo-2-butenyl pharmacophore

Several series of compounds containing the 1,4-dioxo-2-butenyl moiety have been prepared as candidate cytotoxins, including the methyl N-arylmaleamates, methyl N-arylfumaramates, and N-arylmaleimides. In addition, the N-arylisomaleimides were synthesized which are the structural isomers of N-arylmaleimides. These compounds were evaluated against human Molt 4/C8 and CEM T-lymphocytes as well as murine L1210 cells. Methyl N-arylfumaramates showed the highest cytotoxic potencies and, in particular, methyl N-(3,4-dichlorophenyl)fumaramate is six times more potent than melphalan towards L1210 cells and is equipotent with this drug in the Molt 4/C8 assay. Electrophilicity of compounds under investigation was demonstrated by carrying out thiolation using model benzyl mercaptan on representative compounds. Methyl N-(3,4-dichlorophenyl)fumaramate and methyl N-(4-chlorophenyl)maleamate inhibited human N-myristoyltransferase, a possible molecular target, in high micromolar range. QSAR and molecular modeling revealed some correlations between different structural features of a number of the molecules and cytotoxic potencies. Methyl N-arylfumaramates were well tolerated in mice in comparison to the analogs in other series of compounds tested. The data obtained in this investigation affords guidelines for preparing new series of molecules with greater potencies.     

Synthesis of N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamides as new selective ligands for sigma receptors

Novel benzofuran-2-carboxamide ligands, which are selective for sigma receptors, have been synthesized via a microwave-assisted Perkin rearrangement reaction and a modified Finkelstein halogen-exchange used to facilitate N-alkylation. The ligands synthesized are the 3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamides (KSCM-1, KSCM-5 and KSCM-11). The benzofuran-2-carboxamide structure was N-arylated and N-alkylated to include both N-phenyl and N-(3-(piperidin-1-yl)propyl substituents, respectively. These new carboxamides exhibit high affinity at the sigma-1 receptor with K_i values ranging from 7.8 to 34 nM. Ligand KSCM-1 with two methoxy substituents at C-5 and C-6 of the benzofuran ring, and K_i = 27.5 nM at sigma-1 was found to be more selective for sigma-1 over sigma-2.     

Novel N-chloroheterocyclic antimicrobials

Antimicrobial compounds with broad-spectrum activity and minimal potential for antibiotic resistance are urgently needed. Toward this end, we prepared and investigated a novel series of N-chloroheterocycles. Of the compounds examined, the N-chloroamine series were found superior over N-chloroamide series in regards to exhibiting high antimicrobial activity, low cytotoxicity, and long-term aqueous stability.     

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.     

Comparison of cytokinin activities of the base,ribonucleoside and 5′- and cyclic-3′,5′-monophosphate ribonucleotides of N6-isopentenyl-, N6-benzyl or 8-bromo-adenine

The cytokinin activities of adenosine 3′,5′-monophosphate, N⁶,O^2″-dibutyryladenosine 3′,5−'monophosphate, 8-bromoadenosine 3′,5′-monophosphate, N⁶-(Δ²-isopentenyl)adenosine 3′,5′-monophosphate, and N⁶-benzyladenosine 3′,5′-monophosphate were determined in the tobacco bioassay and compared with the activities of the corresponding non-cyclic nucleotides, nucleosides and bases of the N⁶-isopentenyl-substituted, N⁶-benzyl-substituted, 8-bromo-substituted, and unsubstituted adenine series. In each of these series the cytokinin activities in decreasing order were: bases ⪢ nucleosides ⪖ nucleotides > cyclic nucleotides. All members of the N⁶-isopentenyl- substituted and N⁶-benzyl-substituted series were highly active cytokinins, reaching maximum activity at concentrations of 1 μM or less, whereas, as expected, all members of the unmodified adenine series were inactive in the tested concentration ranges of up to 180 and 200 μM for adenosine and adenine, and 40 μM for the adenine nucleotides. Members of the 8-bromo-substituted adenine series were much weaker cytokinins than the N⁶-substituted adenine derivatives but showed activity in the same sequence starting at a concentration of about 5 μM. Thus, in the cases of 8-bromoadenosine 3′,5′-monophosphate and N⁶,O^2′-dibutyryl-adenosine 3′,5′-monophosphate, both of which have been reported to promote cell division and growth of plant tissues, the cytokinin activity is related to the 8-bromo substituent and to the N⁶-butyryl substituent, respectively, rather than to the 3′,5′-cyclic monophosphate moiety.     

Basic structure of the oligosaccharide repeating-unit of the Shigella flexneri O-antigens.

The reaction of sodium D-glucuronate with a synthetic peptide, AcTyrLysGlyNH₂ acetate, under physiological conditions, gave as major product the sodium salt of AcTyr-N-(D-arabino-5-carboxy-2,3,4,5-tetrahydroxy-1-pentenyl)-N-(D-arabino- 5-carboxy-3,4,5-trihydroxy-2-oxopentylidene)LysGlyNH₂ (2). The structure was elucidated on the basis of p.m.r., ¹³C-n.m.r., i.r., and u.v. spectra, and pH titration. Compound 2 is the product of oxidation of the sodium salt of AcTyr-N,N-bis(D- arabino-5-carboxy-2,3,4,5-tetrahydroxy-1-pentenyl)LysGlyNH₂, the bis-enol form of the di-D-fructuronic acid peptide obtained through the Amadori rearrangement. A new type of condensation that gives a product having a conjugated enol-keto-immonium group might take place when D-glucuronic acid reacts with peptides or proteins containing a lysine residue.     

Synthesis of 3-(3-hydroxyphenyl)pyrrolidine dopamine D3 receptor ligands with extended functionality for probing the secondary binding pocket

A series of 3-(3-hydroxyphenyl)pyrrolidine analogues which incorporate N-alkyl groups and N-butylamide-linked benzamide functionality have been synthesized and their in vitro binding affinities at human dopamine receptors have been evaluated. Our ligand design strategy was to take the 3-(3-hydroxyphenyl)pyrrolidine scaffold and extend functionality from the orthosteric binding site to the secondary binding pocket for enhancing affinity and selectivity for the D₃ receptor. The N-alkyl analogues constitute a homologous series from N-pentyl to N-decyl to probe the length/bulk tolerance of the secondary binding pocket of the D₃ receptor. Enantiomeric 3-(3-hydroxyphenyl)pyrrolidine analogues were also prepared in order to test the chirality preference of the orthosteric binding site for this scaffold. Benzamide analogues were prepared to enhance affinity and/or selectivity based upon the results of the homologous series.     

Protein immobilization on poly-(N-substituted) acrylamides

A series of water-soluble polymers containing side chains derived from N-acryloyl-β-alanine, N-ethylacrylamide and N-[3-(N′,N′,N′-trimethylammonio)propyl] acylamide chloride has been prepared and characterized. A related series of insoluble gels was also prepared. Protein may be attached to these materials by means of amide bond formation between carboxyl groups on the polymers and amino groups of the protein; the preparation and characterization of conjugates formed with α-chymotrypsin are described. Polymers bearing negatively or positively charged side chains are attached to this enzyme at only a single amino acid and the integrity of the active site is largely preserved in these systems. The corresponding gels are not able to bind as much enzyme as are the soluble polymers and bound enzyme is less active in these cases.     

12-Substituted 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phenanthridines as novel topoisomerase I-targeting antitumor agents

2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine and a few of its 12-substituted analogs are active as TOP1-targeting agents. Studies were performed to further evaluate the potential of this series of non-camptothecin TOP1-targeting agents. The influence of a hydroxymethyl, formyl, N,N-dimethylaminomethyl, 2-(N,N-dimethylamino)ethyl, 3-(N,N-dimethylamino)propyl), and 4-(N,N-dimethylamino)butyl substituent at the 12-position on TOP1-targeting activity and tumor cell growth was evaluated. In addition, the relative pharmacologic activities of the 12-carboxamide analog, as well as its N-methyl and N,N-dimethyl derivatives were assessed.     

Specificity and stereospecificity of α-chymotrypsin

1. The optically pure p-nitrophenyl esters of the d and l enantiomers of N-acetyl-tryptophan, N-acetylphenylalanine and N-acetyl-leucine, and the p-nitrophenyl ester of N-acetylglycine, have been prepared. 2. These materials are all substrates of α-chymotrypsin, and the rates of deacylation of the corresponding acyl-α-chymotrypsins have been determined. 3. As the size of the amino acid side chain increases, the l series deacylate progressively faster than the N-acetylglycyl-enzyme, and the d series progressively more slowly. 4. The results are interpreted in terms of a three-locus model of the enzyme's active site, which accounts for the interrelationship between substrate specificity and stereospecificity observed. 5. The concepts of negative specificity and of specificity saturation are introduced.     

The NOTCH Locus of DROSOPHILA HYDEI: Alleles, Phenotypes and Functional Organization

The Notch (N) locus of Drosophila hydei and a series of its alleles and phenotypes are described. Some models are discussed to explain the opposite effects of some alleles on the structure of the wing, the neomorphic action of N^Ax over typical N alleles and the interaction with the mutation Costal-nick (Cnk).     

Formation of Chromosome Rearrangements by P Factors in Drosophila

We studied a collection of 746 chromosome rearrangements all induced by the activity of members of the P family of transposable elements in Drosophila melanogaster. The chromosomes ranged from simple inversions to complex rearrangements. The distribution of complex rearrangement classes was of the kind expected if each rearrangement came about from a single multibreak event followed by random rejoining of chromosome segments, as opposed to a series of two-break events. Most breakpoints occurred at or very near (within a few hundred nucleotide pairs) the sites of preexisting P elements, but these elements were often lost during the rearrangement event. There were also a few cases of apparent gain of P elements. In cases in which both breakpoints of an inversion retained P elements, that inversion was capable of reverting at high frequencies to the original sequence or something close to it. This reversion occurred with sufficient precision to restore the function of a gene, held-up-b, which had been mutated by the breakpoint. However, some of the reversions had acquired irregularities at the former breakpoints that were detectable either by standard cytology or by molecular methods. The revertants themselves retained the ability to undergo further rearrangements depending on the presence of P elements. We interpret these results to rule out the simplest hypotheses of rearrangement formation that involve cointegrate structures or homologous recombination. The data provide a general picture of the rearrangement process and its possible relationship to transposition.     

O-esters of N-acylhydroxylamines: toxicity and enhancement of sister-chromatid exchange in chinese hamster ovary cells

2-Naphthohydroxamic acid, 4-N-butoxyphenylacetohydroxamic acid, and their O-sulfonate, O-formate, O-acetate, and O-propionate derivatives were studied for cytotoxicity and sister chromatid exchange (SCE) induction in Chinese hamster ovary (CHO) cells. 2-Naphthylisocyanate, 2-aminonaphthalene (2 Lossen rearrangement products of the O-sulfonate derivative of 2-naphthohydroxamic acid), and N-methyl-2-naphthohydroxamic acid were also studied. All of these chemicals were cytotoxic and significantly increased SCE frequency, although there was a lack of correlation between these 2 effects. 2-Naphthylisocyanate and 2-aminonaphthalene were not as cytotoxic nor as active in inducing SCEs as the O-sulfonate ester of 2-naphthohydroxamic acid suggesting that the cytotoxicity and SCE induction of the latter are not due to its decomposition products.     

Inhibitory properties of N-nicotinyl-N' (substituted) urea analogs of NAD.

A series of N-nicotinyl- and N-isonicotinyl-N′-(substituted) ureas were synthesized by a condensation of the appropriate amide with various alkyl or aryl isocyanates, and examined as potential antimetabolites of nicotinamide. No significant microbial toxicity was observed; however, several derivatives in the nicotinyl series proved to be toxic to fish, especially N-nicotinyl-N′-hexylurea which possessed a TL₅₀ of 27 μg/ml. The toxicity was reversed by supplements of nicotinamide but not tryptophan, and may be due to the formation of an inactive NAD complex through the mediation of NADase. Evidence for this possibility is presented by the formation in vitro of an N-nicotinyl[7-¹⁴C]N′-ethylurea-NAD analog which was characterized through spectral, chemical, and chromatographic studies.     

Structural manipulation of aporphines via C10 nitrogenation leads to the identification of new 5-HT7AR ligands

Aporphine alkaloids containing a C10 nitrogen motif were synthesized and evaluated for affinity at 5-HT_1AR, 5-HT_2AR, 5-HT₆R and 5-HT_7AR. Three series of racemic aporphines were investigated: 1,2,10-trisubstituted, C10 N-monosubstituted and compounds containing a C10 benzofused aminothiazole moiety. The 1,2,10-trisubstituted series of compounds as a group displayed modest selectivity for 5-HT_7AR and also had moderate 5-HT_7AR affinity. Compounds from the C10 N-monosubstituted series generally lacked affinity for 5-HT_2AR and 5-HT₆R and showed strong affinity for 5-HT_1A or 5-HT_7AR. Compounds in this series that contained an N6-methyl group were up to 27-fold selective for 5-HT_7AR over 5-HT_1AR, whereas compounds with an N6-propyl substituent showed a reversal in this selectivity. The C10 benzofused aminothiazole analogues showed a similar binding profile as the C10 N-monosubstituted series i.e. strong affinity for 5-HT_1AR or 5-HT_7AR, with selectivity between the two receptors being similarly influenced by N6-methyl or N6-propyl substituents. Compounds 29 and 34a exhibit high 5-HT_7AR affinity, excellent selectivity versus dopamine receptors and function as antagonists in 5-HT_7AR cAMP-based assays. Compounds 29 and 34a have been identified as new lead molecules for further tool and pharmaceutical optimization.