Total asymmetric synthesis of (-)-conduramine B-1 and of its enantiomer. N-Benzyl derivatives of conduramine B-1 are beta-glucosidase inhibitors

The 'naked sugars' (+)- and (-)-7-oxabicyclo[2.2.1]hept-5-en-2-one have been converted into (-)-conduramine B-1 ((-)-3) and its enantiomer (+)-3, respectively. They have been condensed with a variety of aldehydes in the presence of NaBH(OAc)(3). The N-substituted derivatives 4 and ent-4 so-obtained have been tested against two alpha-glucosidases, two amyloglucosidases, two beta-glucosidases and one beta-xylosidase for their inhibitory activities. Although (-)-3 and (+)-3 do not inhibit any of these enzymes at 1mM concentration, N-benzylated derivatives of (-)-conduramine B-1 are selective and competitive inhibitors of beta-glucosidases with K(i) in low micromolecular range.     

Derivatization and Template-Guided Ligation of Oligodeoxyribonucleotides Using Cyanogen Bromide and N-Substituted Morpholines

Cyanogen bromide has been found to induce the template-guided condensation of oligonucleotides only in the presence of N-substituted morpholines. Based on ³¹ P,¹ H and¹³ C NMR spectroscopy data, the mechanism of the phosphomonoester group activation by cyanogen bromide in N-substituted morpholine buffers is suggested. It has also been shown that BrCN can be used for the synthesis of oligonucleotide derivatives in aqueous solution.     

Synthesis and hydrolytic evaluation of acid-labile imine-linked cytotoxic isatin model systems

In this study a series of isatin-based, pH-sensitive aryl imine derivatives with differing aromatic substituents and substitution patterns were synthesised and their acid-catalysed hydrolysis evaluated. These derivatives were functionalised at the C3 carbonyl group of a potent N-substituted isatin cytotoxin and were stable at physiological pH but readily cleaved at pH 4.5. Observed rates of hydrolysis for the embedded imine-acid moiety were in the order para-phenylpropionic acid>phenylacetic acid (para>meta)>benzoic acid (meta>para). The ability to fine-tune hydrolysis rates in this way has potential implications for optimising imine linked, tumour targeting cytotoxin-protein conjugates.     

Fluorinated isatin derivatives. Part 1: Synthesis of new N-substituted (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatins as potent caspase-3 and -7 inhibitors

A series of new N-substituted (S)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin derivatives has been synthesized and tested as inhibitors of caspases-3 and -7, which are known to be downstream enzymes critical in the execution of apoptosis. N-Propyl- and N-butyl isatins, as well as the corresponding terminal alcohols and regioisomeric fluorobutyl derivatives were shown to be excellent inhibitors having different binding potencies for caspases-3 and -7. In contrast, the corresponding fluoroethyl and fluoropropyl compounds were about 100–1000 times less active. Fluorinated N-benzyl isatins as well as trifluoroalkyl and difluoroalkyl derivatives were moderate inhibitors. However, isatins bearing different alkylether groups at N-1 are very weak or not active as inhibitors of caspases-3 and -7.     

The design of fluorescent probes which bind to the active centre of guanidinobenzoatase. Application to the location of cells possessing this enzyme

Cells possessing a known enzymic activity may be located by fluorescent probes designed to act as competitive inhibitors of this enzyme. We have prepared a series of dansyl N-substituted guanidino derivatives which bind to the active centre of guanidinobenzoatase. 9-Aminoacridine also acts as a competitive inhibitor and behaves similarly to these guanidino derivatives. These fluorescent probes have been used to locate tumour cells possessing this enzyme in thin sections of fixed tissue by employing fluorescent microscopy.     

Antitumor studies. part 3: design, synthesis, antitumor activity, and molecular docking study of novel 2-methylthio-, 2-amino-, and 2-(N-substituted amino)-10-alkyl-2-deoxo-5-deazaflavins

Various novel 10-alkyl-2-deoxo-2-methylthio-5-deazaflavins have been synthesized by reaction of 6-(N-alkylanilino)-2-methylthiopyrimidin-4(3H)-ones with Vilsmeier reagent. The similar 2-(N-substituted amino) derivatives were prepared by nucleophilic replacement reaction of the 2-methylthio moiety by appropriate amines. The 2-oxo derivatives (i.e., 5-deazaflavins) were obtained by acidic hydrolysis of the 2-methylthio derivatives. The antitumor activities against CCRF-HSB-2 and KB cells and the antiviral activities against HSV-1 and HSV-2 have been investigated in vitro, and many compounds showed promising antitumor activities. Furthermore, AutoDock molecular docking into PTK has been done for lead optimization of these compounds as potential PTK inhibitors. Whereas, the designed 2-deoxo-5-deazaflavins connected with amino acids at the 2-position exhibited the good binding affinities into PTK with more hydrogen bonds.     

Carbonic anhydrase inhibitors. Novel sulfanilamide/acetazolamide derivatives obtained by the tail approach and their interaction with the cytosolic isozymes I and II, and the tumor-associated isozyme IX

A series of sulfonamides has been obtained by reacting sulfanilamide or 5-amino-1,3,4-thiadiazole-2-sulfonamide with omega-chloroalkanoyl chlorides, followed by replacement of the omega-chlorine atom with secondary amines. Tails incorporating heterocyclic amines belonging to the morpholine, piperidine and piperazine ring systems have been attached to these sulfonamides, by means of an alkanoyl-carboxamido linker containing from two to five carbon atoms. The new derivatives prepared in this way were tested as inhibitors of three carbonic anhydrase (CA, EC 4.2.1.1) isozymes, the cytosolic isozymes CA I and II, and the catalytic domain of the transmembrane, tumor-associated isozyme CA IX. Several low nanomolar CA I and CA II inhibitors were detected both in the aromatic and heterocyclic sulfonamide series, whereas the best hCA IX inhibitors (inhibition constants in the range of 22-35 nM) all belonged to the acetazolamide-like derivatives.     

Mammalian chymotrypsin-like enzymes. Comparative reactivities of rat mast cell proteases, human and dog skin chymases, and human cathepsin G with peptide 4-nitroanilide substrates and with peptide chloromethyl ketone and sulfonyl fluoride inhibitors

The extended substrate binding sites of several chymotrypsin-like serine proteases, including rat mast cell proteases I and II (RMCP I and II, respectively) and human and dog skin chymases, have been investigated by using peptide 4-nitroanilide substrates. In general, these enzymes preferred a P1 Phe residue and hydrophobic amino acid residues in P2 and P3. A P2 Pro residue was also found to be quite acceptable. The S4 subsites of these enzymes are less restrictive than the other subsites investigated. The substrate specificity of these enzymes was also investigated by using substrates which contain model desmosine residues and peptides with amino acid sequences of the physiologically important substrates angiotensin I and angiotensinogen and alpha 1-antichymotrypsin, the major plasma inhibitor for chymotrypsin-like enzymes. These substrates were less reactive than the most reactive tripeptide reported here, Suc-Val-Pro-Phe-NA. The thiobenzyl ester Suc-Val-Pro-Phe-SBzl was found to be an extremely reactive substrate for the enzymes tested and was 6-171-fold more reactive than the 4-nitroanilide substrate. The four chymotrypsin-like enzymes were inhibited by chymostatin and N-substituted saccharin derivatives which had KI values in the micromolar range. In addition, several potent peptide chloromethyl ketone and substituted benzenesulfonyl fluoride irreversible inhibitors for these enzymes were discovered. The most potent sulfonyl fluoride inhibitor for RMCP I, RMCP II, and human skin chymase, 2-(Z-NHCH2CONH)C6H4SO2F, had kobsd/[I] values of 2500, 270, and 1800 M-1 s-1, respectively. The substrates and inhibitors reported here should be extremely useful in elucidating the physiological roles of these proteases.     

Carbonic anhydrase inhibitors. Selective inhibition of human tumor-associated isozymes IX and XII and cytosolic isozymes I and II with some substituted-2-mercapto-benzenesulfonamides

A series of 2-mercapto-substituted-benzenesulfonamides has been prepared by a unique two-step procedure starting from the corresponding 2-chloro-substituted benzenesulfonamides. Compounds bearing an unsubstituted mercapto group and the corresponding S-benzoyl derivatives were investigated as inhibitors of four isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), i.e., the cytosolic, ubiquitous isozymes CA I and II, as well as the transmembrane, tumor associated isozymes CA IX and XII. These derivatives were medium potency hCA I inhibitors (K(I)s in the range of 1.5-5.7 microM), two derivatives were strong hCA II inhibitors (K(I)s in the range of 15-16 nM), whereas the others showed weak activity. These compounds inhibited hCA IX with inhibition constants in the range 160-1950 nM and hCA XII with inhibition constants in the range 1.2-413 nM. Some of these derivatives showed a certain degree of selectivity for inhibition of the tumor-associated over the cytosolic isoforms, being thus interesting leads for the development of potentially novel applications in the management of hypoxic tumors which overexpress CA IX and XII.     

Antifouling Activities of N-Substituted Imides: Antimicrobial Activities and Inhibition of Mytilus edulis Phenoloxidase

In the search for novel biodegradable antifouling agents, a series of imides (N-substituted maleimides and succinimides) have been synthesized. A large majority of N-substituted maleimides and succinimides showed an antimicrobial activity toward gram-positive and gram-negative bacteria and fungi of marine origin with minimal inhibition concentrations in the range of 6 to 24 mg/ml. The imides with an alkyl substituent showed higher activities than aromatic analogues, but structure-activity relationships were not clearly established. Some compounds were powerful inhibitors of Mytilus edulis phenoloxidase. This inhibition was noncompetitive as demonstrated with 2 maleimides, a 3-acetoxy succinimide and a succinimide. Thus, this family of products has potential interest as antifouling agents.     

Synthesis and glycosidase inhibitory activity of some N-substituted 6-deoxy-5a-carba-beta-DL- and L-galactopyranosylamines

Chemical modification of 5a-carba-beta-DL-fucopyranosylamine (3) generated six N-substituted derivatives 9a-f, among which N-octyl 9b, decyl 9c, and phenylbutyl ones 9f were found to be very strong beta-galactosidase as well as beta-glucosidase inhibitors. The inhibitory activity appeared attributable to D-enantiomers from biological assays of prepared L-enantiomers. Therefore, 6-deoxy-5a-carba-beta-D-galactopyranosylamine (D-3) might be a promising lead compound for further design of new carba sugar-type beta-galactosidase inhibitors.     

Interactions of thrombin with benzamidine-based inhibitors.

Trypsin and trypsin-like enzymes cleave C-terminal bonds of the basic amino acids Arg and Lys. Inhibitors of these enzymes have been found not only among Arg and Lys derivatives but also with structurally related benzamidines. Especially cyclic amides of 4-amidinophenylalanine were found to be inhibitors of thrombin. The most potent selective thrombin inhibitor of these type is N alpha-(beta-naphthylsulfonylglycyl)-4-amidinophenylalanine piperidine. From the X-ray crystal structures of thrombin and trypsin-inhibitor complexes the thrombin complexes formed with inhibitors derived from amidinophenylalanine have been modeled. These models allow valuable predictions to design inhibitors of improved selection and binding properties. Most recently, also the X-ray crystal structures of complexes of inhibitors with bovine thrombin have been solved.     

Polyadenylate polymerase from cytoplasm and nuclei of N.I.H.-Swiss mouse embryos.

Poly (A) polymerase activity from cytoplasm and nuclei of 12-16-day-old mouse embryos has been partially purified by (NH4)2SO4 fractionation, DEAE-cellulose, phosphocellulose and tRNA-Sepharose affinity chromatography, and their properties have been compared. The nuclear and cytoplasmic enzymes exhibit similar chromatographic elution profiles, and similar biochemical and physical properties. Poly(A) polymerase has an absolute requirement for a divalent cation, ATP and an oligo- or polyribonucleotide primer. With tRNA, the divalent salt concentrations for optimum enzyme activity are 1 mM MnCl2 or 10 mM MgCl2. The enzyme activity with MnCl2 is 10-15-fold higher than that with MgCl2. The molecular weight of the native enzyme is about 65 000 and its sedimentation coefficient is around 4.5 S. The average chain length synthesized by the enzyme is between 10 and 13 nucleotides. The inhibitors of RNA polymerase do not affect poly (A) polymerase activity; however, some synthetic rifamycin SV derivatives are potent inhibitors of this enzyme.     

Synthesis and inhibitory activity of acyl-peptidyl-pyrrolidine derivatives toward post-proline cleaving enzyme; a study of subsite specificity.

Several pyrrolidine derivatives have been synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain. Almost all the compounds tested in this study inhibited the activity of both enzymes at low IC50 values (from nM to microM) but a specificity difference was observed with alkylacyl-peptidyl-pyrrolidine derivatives which strongly inhibited only the bacterial enzyme. The most effective inhibitors have a proline residue on their P2 sites and a substituted or unsubstituted phenoxybutyryl moiety on their P3 sites. Thus phenoxybutyryl-prolyl-pyrrolidine is the most effective partial structure of the inhibitors. The best inhibitors found were: 4-(4-benzylphenoxy)butyryl-prolyl-pyrrolidine for bacterial enzyme (IC50 1.4 nM) and 4-phenylbutyryl-thioprolyl-pyrrolidine for bovine brain enzyme (IC50 67 nM). In the passive avoidance test, using amnesic rats experimentally induced with scopolamine, the pyrrolidine derivatives which had potent inhibitory activity toward post-proline cleaving enzymes also showed strong anti-amnesic activities at doses of 1-5 mg/kg, i.p.     

Evaluation of 4'-substituted bicyclic pyridones as non-steroidal inhibitors of steroid 5alpha-reductase

4'-Substituted bicyclic pyridones were prepared and evaluated as non-steroidal inhibitors of type 1 and 2 steroid 5alpha-reductase (SR). A range of 4'-substituents were incorporated into the bicyclic scaffold to investigate SAR within and across different classes of non-steroidal inhibitors of SR. Bicyclic pyridones containing a 4'-benzoyl or long carbon chain tether showed more potent inhibition against type 1 SR than inhibitors with N-substituted acetamide groups in the 4'-position. SAR derived from 4'-substituted bicyclic pyridones reported here do not correlate with SAR derived from known potent 4'-substituted biaryl acid SR inhibitors. A 4'-benzoyl group is favoured by the active site in both isozymes.     

Synthesis and evaluation of 6-methylene-bridged uracil derivatives. Part 1: discovery of novel orally active inhibitors of human thymidine phosphorylase

A series of novel 6-methylene-bridged uracil derivatives have been prepared as inhibitors of human thymidine phosphorylase (TP). To enhance the in vivo antitumor activity of fluorinated pyrimidine 2'-deoxyribonucleosides such as 2'-deoxy-5-(trifluoromethyl)uridine (F(3)dThd), a potent TP inhibitor preventing their degradation to an inactive compound, has become a target of medicinal chemistry. We present here the synthesis and evaluation of novel human TP inhibitors. Introduction of an N-substituted aminomethyl side chain at the 6-position of 5-chlorouracil has improved water solubility and enhanced inhibitory activity compared with the known TP inhibitor, 6-amino-5-chlorouracil. Compound 42 was reasonably well absorbed in mice after oral administration. When combined with F(3)dThd, compound 42 exerted its TP inhibitory potency by increasing the maximum plasma concentrations of the former as evidenced in experiments with monkeys. Positive changes in pharmacokinetic profile were accompanied by the enhanced in vivo antitumor activity of this combination when compared to F(3)dThd alone, in mice bearing human tumor xenografts. Both biochemical and pharmacological effects appeared to fit the concept as anticipated.     

Functionalised dithiocarbamate complexes: Complexes based on indoline, indole and substituted piperazine backbones - X-ray crystal structure of [Ni(S2CNC3H6C6H4)2]

A range of new nickel, copper and zinc bis(dithiocarbamate) complexes has been prepared from secondary amines with functionalised backbones. These include complexes derived from iso-indoline, tetrahydro-isoindoline, 1,2,3,4-tetrahydroisoquinoline and a number of functionalised piperazines. The crystal structure of [Ni(S₂CNC₃H₆C₆H₄)₂] derived from 1,2,3,4-tetrahydroisoquinoline is reported.     

N-[1-Aryl-2-(1-imidazolo)ethyl]-guanidine derivatives as potent inhibitors of the bovine mitochondrial F1F0 ATP hydrolase

A series of substituted guanidine derivatives were prepared and evaluated as potent and selective inhibitors of mitochondrial F(1)F(0) ATP hydrolase. The initial thiourethane derived lead molecules possessed intriguing in vitro pharmacological profiles, though contained moieties considered non-drug-like. Analogue synthesis efforts led to compounds with maintained potency and superior physical properties. Small molecules in this series which potently and selectivity inhibit ATP hydrolase and not ATP synthase may have utility as cardioprotective agents.     

Inhibition of proteases with enkephalin-analogue inhibitors.

N-peptidyl-O-acyl hydroxylamines have proven to be effective and selective mechanism-based inhibitors of serine and cysteine proteases as demonstrated using enzymes with specificities for hydrophobic amino acids at the cleavage site. Here, we report for the first time the inhibition of proteases able to accommodate cationic amino acid side chains in their binding pockets using compounds of this inhibitor class. Trypsin and papain are inactivated by enkephalin-analogue diacyl hydroxylamines in a time-dependent and irreversible manner exhibiting second-order rate constants in the range of 100-1000 M-1.s-1. In contrast, human cerebrospinal fluid dynorphin-converting enzyme (hCSFDCE) is inhibited only moderately by these inhibitors. Mechanistic implications have been derived.     

The inhibition of human cytomegalovirus (hCMV) protease by hydroxylamine derivatives

Aryl hydroxylamine derivatives have been synthesised that are some of the most potent inhibitors of hCMV protease prepared to date (IC50 14-60 nM). Mass spectrometry studies indicate that oxazinone derived hydroxylamines inhibit the enzyme by acylation of Ser132 whereas non-oxazinone derived hydroxylamines appear to inhibit via formation of a sulfinanilide at Cys138.