Synthesis of amino-hydroxy-benzocycloheptenones as potent, selective, non-peptidic dinuclear zinc metalloaminopeptidase inhibitors.

Racemic trisubstituted benzocycloheptanes were synthesized and evaluated for their ability to inhibit metalloaminopeptidase activities. A highly selective nanomolar inhibitor of a prototypical 'two zinc' aminopeptidase from the M28 family was observed with these tridentate species, while bidentate analogs proved to be highly selective for the 'one zinc' M1 family of enzymes. The selectivity profile of these new, low molecular weight structures may guide the design of specific, non-peptidic inhibitors of binuclear aminopeptidases.

Rapid and efficient synthesis of a novel series of substituted aminobenzosuberone derivatives as potent, selective, non-peptidic neutral aminopeptidase inhibitors.

Racemic 5-substituted 7-aminobenzocyclohepten-6-one were synthesized and evaluated for their ability to inhibit metalloaminopeptidase activities. Unexpectedly, 5-thio substituted compounds showed enhanced inhibition potency with K(i) values in the nanomolar range against the 'one zinc' aminopeptidases from the M1 family, while most of them were rather poor inhibitors of the 'two zincs' enzymes from the M17 family. This interesting selectivity profile may guide the design of new, specific inhibitors of target mammalian aminopeptidases with one active site zinc.

A novel amino-benzosuberone derivative is a picomolar inhibitor of mammalian aminopeptidase N/CD13.

A new class of low molecular weight, highly potent and selective non peptidic inhibitors of aminopeptidase N (APN/CD13) is described. We report the synthesis and in vitro evaluation of racemic substituted analogues of 7-amino-benzocyclohepten-6-one 1a. We investigated various substitutions on the aromatic ring with phenyl and halogen groups. In vitro kinetic studies revealed that these compounds are among the most effective APN/CD13 inhibitors found so far. Hydrophobic substituents placed at position 1 or 4 on the cycloheptenone 1a led to the potent compounds 1c-h,b'-c',f',h' with K(i) in the nanomolar range. The key finding of the present work was the observed additive effect of 1,4-disubstitutions which led to the discovery of the picomolar inhibitor 1d' (K(i)=60 pM). The designed inhibitors retain the selectivity of our lead structure 1a towards selected members of the aminopeptidase family, combined with an impressive increase in inhibitory potency and a conserved stability.

Synthesis of 4-amino-4,5-dideoxy-L-lyxofuranose derivatives and their evaluation as fucosidase inhibitors.

The nitrone 4 (4,5-dideoxy-4-hydroxylamino-3,4-O-isopropylidene-L-lyxofuranose) was synthesised from D-ribose and used as key intermediate for the preparation of fucosidase inhibitors. We describe two transformations of 4. Hydrolysis with aqueous sulfur dioxide gave the known potent nanomolar inhibitor 4-amino-4,5-dideoxy-L-lyxofuranose (3). 1,3-Dipolar cycloaddition with enol ethers led to the related 1,2,5,6-tetradeoxy-2,5-imino-L-altroheptonic ester 2a, acid 2b and the corresponding heptitol 2c. The new iminosugars have been evaluated for their inhibitory activity against α-L-fucosidase from bovine kidney. The alcohol 2c turned out to be a potent inhibitor in the same range as the amino-sugar 3 (K(i)=8 vs 10nM).

Amino-benzosuberone: a novel warhead for selective inhibition of human aminopeptidase-N/CD13.

This paper describes the design and synthesis of compounds belonging to a novel class of highly selective mammalian CD13 inhibitors. Racemic homologues of 3-amino-2-tetralone 1 were synthesised and evaluated for their ability to selectively inhibit the membrane-bound, zinc-dependent aminopeptidase-N/CD13 (EC 3.4.11.2). Some of these novel non-peptidic compounds are potent, competitive inhibitors of the mammalian enzyme, with K(i) values in the low micromolar range in spite of their minimal size (MW <200 Da). Moreover, they show an interesting selectivity profile against representative members of the aminopeptidase family, that is leucine aminopeptidase (EC 3.4.11.1), Aeromonas proteolytica aminopeptidase (EC 3.4.11.10) and the aminopeptidase activity of leukotriene A4 hydrolase (EC 3.3.2.6). The amino-benzosuberone derivative 4 is the most promising compound in terms of potency, stability and selectivity. A hypothetical binding mode of 4 to the catalytic zinc and several conserved active site residues is proposed, based on the observed structure-activity relationships, structural insights from aminopeptidase-N homologues of known three-dimensional structure.

Synthesis of all-cis 2,5-imino-2,5-dideoxy-fucitol and its evaluation as a potent fucosidase and galactosidase inhibitor.

We here describe a simple and efficient synthetic method for a non-hydrolysable precursor of a GDP-fucose analogue: The synthesis of the racemic aminofuranofucitol 3 from sorbic alcohol by nitroso-Diels-Alder reaction. This 'all-cis-pyrrolidine', with all substituents occupying a cis position, has been determined as a potent inhibitor of α-L-fucosidase and a moderate inhibitor of α- and ß-D-galactosidase. The good recognition of this fucose moiety analogue by specific enzymes is thus confirmed. The C-anomeric bond in this particular structure is in the ß-position and makes this compound an interesting candidate for further chemical modifications. Influence of the methyl and hydroxymethyl groups on the inhibition potency is discussed.

Photoinduced coupled charge and proton transfers in gradually twisted phenol-pyridinium biaryl series.

A detailed photophysical analysis of a phenol-pyridinium biphenyl series with gradual twisted geometry is presented in this paper. The low-energy CT absorption band of the compounds undergoes a decrease of intensity with a progressive blue shift by increasing the twist angle of the central bond (Theta(AD)). These effects are well described and quantified within the framework of the Mulliken-Murrel approach, which allows us to extend such a model to the charge-shift process. The biaryl compounds exhibit broadened fluorescence bands assigned to the radiative deactivation of a charge shift (CSh) species generated by an intramolecular twisting relaxation of the locally excited (LE) state. Parallel to the rotamerism of the central single bond, excited-state proton-transfer (ESPT) processes are occurring from both excited states and lead to the nonemissive phenolate forms. Solvatochromic shifts of the emission bands are correlated by the Kamlet-Taft parameters (pi*, alpha, and beta). The correlation first confirms the pi* dependence of the CSh band shift but also demonstrates a clear beta dependence. The contribution of the latter parameter to the band hypsochromy is markedly increasing with Theta(AD). Such an unusual effect was ascribed to a much higher ESPT rate relative to the highly twisted conformation with respect to that of more planar geometry. Despite the suppression of the geometrical relaxation in ethanol glass at 77 K, the fluorescence of the phenolate species produced by ESPT from LE state is detected. The relative increase of its fluorescence band intensity with Theta(AD) confirms the gradual enhancement of the excited states acidity.

Photoinduced intramolecular electron transfer in a 2,7-diaminofluorene chromophore decorated with two benzophenone subunits.

An extensive photophysical analysis of a 2,7-bis-(N-4-methoxyphenyl-N-phenylamino)fluorene derivative covalently linked with two benzophenone moieties is presented. A systematic comparison with a model chromophore without benzophenone was performed. For both chromophores, the electronic properties of the ground states are completely equivalent indicating that benzophenone subunits do not exhibit any electronic interaction with the diaminofluorene core. However, at the singlet excited state, the presence of benzophenones induces the occurrence of additional non-radiative de-excitation pathways. Even the intersystem crossing rate is significantly increased with respect to that of the model one. A photoinduced intramolecular electron transfer (PIET) from diaminofluorene to benzophenone subunits is proposed as the most efficient quenching process. At low polar solvent, the emission of an exciplex confirms the PIET process and the occurrence of a partial charge separation between donor and acceptor parts.

Two-photon absorption and polymerization ability of intramolecular energy transfer based photoinitiating systems.

We design a new photoinitiating system where the two-photon absorption of a 2,7 bisaminofluorene moiety leads to the photoactivation of a camphorquinone subunit through a Förster-type intramolecular energy transfer: the application to a two-photon polymerization reaction is demonstrated.

Theoretical and experimental study of the Norrish I photodissociation of aromatic ketones.

A set of selected acetophenone derivatives was investigated using absorption and emission spectroscopy, laser flash photolysis and DFT calculations. The triplet state lifetimes and the activation energy of the cleavage reaction were measured. Computed triplet-triplet absorption spectra were found in very good agreement with the experimental ones. Bond dissociation energies, activation energies, partial charges, ground state geometries were calculated. The transition state theory TST was successfully used to calculate the cleavage rate constants: a very good correlation was found between the experimental and the calculated values. It is found that the entropy change influences the preexponential factor. This study also points out the role of the partial charges in the transition state, although this effect alone does not account for the reaction rate constants.

Synthesis and evaluation of amino-threoses in D- and L-series: are five membered ring amino-sugars more potent glycosidase inhibitors than the six membered ones?

Cyclic D- and L-4-aminothreose were synthesised from ethyl D- and L-tartrate, respectively. D-aminothreose was a potent inhibitor of alpha-glucosidase and of alpha-mannosidase. From the glycosidase inhibition potencies of the four 4-amino-4-deoxy-tetroses, the contribution of binding of each functionality of the 5 and 6 membered ring amino-sugars towards the various glycosidases is discussed.

Synthesis and structure activity relationships of novel non-peptidic metallo-aminopeptidase inhibitors.

Racemic derivatives of 3-amino-2-tetralone were synthesised and evaluated for their ability to inhibit metallo-aminopeptidase activities. New compounds substituted in position 2 by methyl ketone, substituted oximes or hydroxamic acids as well as heterocyclic derivatives were evaluated against representative members of zinc-dependent aminopeptidases: leucine aminopeptidase (E.C. 3.4.11.1), aminopeptidase-N (E.C. 3.4.11.2), Aeromonas proteolytica aminopeptidase (E.C. 3.4.11.10), and the aminopeptidase activity of leukotriene A(4) hydrolase (E.C. 3.3.2.6). Several compounds showed K(i) values in the low micromolar range against the 'one-zinc' aminopeptidases, while most of them were rather poor inhibitors of the 'two-zinc' enzymes. This interesting selectivity profile may guide the design of new, specific inhibitors of target mammalian aminopeptidases with one active site zinc.

Asymmetric synthesis of the L-fuco-nojirimycin, a nanomolar alpha-L-fucosidase inhibitor.

We describe the asymmetric synthesis of the 5-amino-5-deoxy-l-fucose (l-fuco-nojirimycin) which appears as a very potent fucosidase inhibitor with a K(i) value of 1 nM.