Rational Design and Synthesis of Novel Dimeric Diketoacid-Containing Inhibitors of HIV-1 Integrase: Implication for Binding to Two Metal Ions on the Active Site of Integrase

Discovery of diketoacid-containing compounds as HIV-1 integrase (IN) inhibitors played a major role in validating this enzyme as an important target for the development of therapeutics against HIV infection. In fact, S-1360, the first clinically used IN inhibitor containing a triazole ring as a bioisostere of a carboxylic acid moiety belongs to this class of compounds. To understand the role of divalent metal-chelating in the inhibition of IN (J. Med. Chem. 2002, 45, 5661-5670), we designed and synthesized a series of novel dimeric diketo-containing compounds with the notion that such dimeric compounds may simultaneously bind to two divalent metal ions on the active site of IN. We rationalized that the two diketo subunits separated by uniquely designed linkers can potentially chelate two metal ions that are either provided from one IN active site or two active sites juxtaposed together in a higher order tetramer. Herein, we show that all the new compounds are highly potent against purified IN with varied selectivity for strand transfer, and that some of the analogues exert potent inhibition of the cytopathic effect of HIV-1 in infected CEM cells. This study represents the first attempt to rationally target two divalent metal ions on the active site of IN and may have potential implications for the design of second generation diketoacid-containing class of inhibitors.

Discovery of alpha,gamma-diketo acids as potent selective and reversible inhibitors of hepatitis C virus NS5b RNA-dependent RNA polymerase

alpha,gamma-Diketo acids (DKA) were discovered from screening as selective and reversible inhibitors of hepatitis C virus NS5b RNA-dependent RNA polymerase. The diketo acid moiety proved essential for activity, while substitution on the gamma position was necessary for selectivity and potency. Optimization led to the identification of a DKA inhibitor of NS5b polymerase with IC(50) = 45 nM, one of the most potent HCV NS5b polymerase inhibitors reported.

Easy access to various natural keto polyunsaturated fatty acids and their corresponding racemic alcohols

Various optically active hydroxy derivatives of polyunsaturated fatty acids were easily oxidised to their corresponding keto derivatives using Dess-Martin periodinane. The reaction was run on the millimolar scale with good yields and without appreciable isomerisation of the surrounding double bonds. Reduction of these keto compounds to yield back the starting alcohols, but now as racemic mixtures, was also conducted using CeCl(3)-NaBH(4), once again without noticeable modification of the stereochemistry of the double bonds. These reactions proved the usefulness of the chemoenzymatic access to oxylipins through the use of lipoxygenases with various regiospecificity, combined with chemical transformations of the formed hydro(pero)xides.

Highly efficient preparation of aryl beta-diketo acids with tert-butyl methyl oxalate

An improved and efficient oxalylation of aryl methyl ketones was accomplished with tert-butyl methyl oxalate. This is the key step in constructing the pharmacophore of aryl beta-diketo acids, which represent a promising new class of HIV-1 integrase inhibitors. Structurally diverse aryl beta-diketo acids, including bisdiketo acids, can be prepared rapidly in impressive yields under mild conditions with this method. Advantages over conventional methods with dimethyl (or diethyl) oxalate were observed in both yield and reaction time.

Efficient synthesis of enantiopure beta-amino-gamma-keto acids from l-homoserine

[reaction: see text] A variety of beta-amino-gamma-keto acids were prepared in four steps from commercially available l-homoserine. The reaction sequence is highlighted by a Ni-catalyzed Grignard addition to a N-protected derivative of l-homoserine. One of the beta-amino-gamma-keto acids was then used to create a beta-peptide trimer composed solely of beta-amino-gamma-keto acids.

Peptidic alpha-ketocarboxylic acids and sulfonamides as inhibitors of protein tyrosine phosphatases

One common approach for designing protein tyrosine phosphatase (PTPase) inhibitors is to incorporate a nonhydrolyzable phosphotyrosine (pTyr) mimic into a peptide substrate for PTPases. This report describes the synthesis of three such nonhydrolyzable pTyr mimics that contain alpha-ketoacid, alpha-hydroxyacid, and methylenesulfonamide functional groups in place of the phosphate. These pTyr mimics were incorporated into the peptide sequence Ac-Asp-Ala-Asp-Glu-X-Leu-NH(2), where X is the pTyr mimic, and analyzed for activity against the Yersinia PTPase and PTP1B.

Use of a pharmacophore model to discover a new class of influenza endonuclease inhibitors

Data from both our own and literature studies of the biochemistry and inhibition of influenza virus endonuclease was combined with data on the mechanism of action and the likely active site mechanism to propose a pharmacophore. The pharmacophore was used to design a novel structural class of inhibitors, some of which were found to have activities similar to that of known influenza endonuclease inhibitors and were also antiviral in cell culture.

Azido-containing aryl beta-diketo acid HIV-1 integrase inhibitors

Aryl beta-diketo acids (ADK) comprise a general class of potent HIV-1 integrase (IN) inhibitors, which can exhibit selective inhibition of strand transfer reactions in extracellular recombinant IN assays and provide potent antiviral effects in HIV-infected cells. Recent studies have shown that polycyclic aryl or aryl rings bearing aryl-containing substituents are components of potent members of this class. Reported herein is the first use of azido functionality as an aryl replacement in beta-diketo acid IN inhibitors. The ability of azido-containing inhibitors to exhibit potent inhibition of IN and antiviral protection in HIV-infected cells, renders the azide group of potential value in the further development of ADK-based IN inhibitors.

Effect of bacteriocin-induced cell damage on the branched-chain amino acid transamination by Lactococcus lactis

The effect of the bacteriocin lacticin 3147 on the branched-chain amino acid transamination by Lactococcus lactis IFPL359 was investigated. The bacteriocin provokes membrane permeabilisation of the cells, rendering them non-viable but metabolically active. Free diffusion of amino acids into the cell was facilitated. In addition, membrane permeabilisation promotes further cell lysis. Both facts render the enzymes more accessible to their substrates and hence increase branched-chain amino acid transamination. This research broadens the spectrum of technological applications of lacticin 3147 in the development of cheese flavour.

Hammett analysis of a C-C hydrolase-catalysed reaction using synthetic 6-aryl-2-hydroxy-6-ketohexa-2,4-dienoic acid substrates

A Hammett plot (rho = -0.71) has been measured for C-C hydrolase enzyme BphD from Pseudomonas LB400, using six 6-aryl-2-hydroxy-6-ketohexa-2,4-dienoic acids synthesised by a Heck coupling strategy.

Divalent and trivalent alpha-ketocarboxylic acids as inhibitors of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPases) are important targets for the treatment of insulin resistance in patients with type II diabetes and as antibacterial agents. As a result, there is a growing interest in the development of potent and specific inhibitors for these enzymes. This paper describes a series of inhibitors that contain two or three alpha-ketocarboxylic acid groups that are designed to form multiple contacts with residues inside or near the active site of phosphatases. The inhibitors have been assayed against three PTPases: the Yersinia PTPase, PTP1B, and LAR. The best of the inhibitors has IC(50) values against the Yersinia PTPase and PTP1B of 0.7 and 2.7 microM, respectively. These divalent and trivalent compounds are significantly more potent than their corresponding monovalent analogues. In addition, they show good selectivity for PTP1B and the Yersinia PTPase as compared to LAR.

Discovery of phenyl alanine derived ketoamides carrying benzoyl residues as novel calpain inhibitors

Novel calpain inhibitors derived from phenyl alanine aldehydes or ketoamides carrying a benzoyl residue were prepared and evaluated for their biological potency. A brief structure-activity relationship elucidated the importance of ortho-substitutents in the benzoyl moiety. The most potent derivative, the ketoamide 19c, exhibited a K(i) of 6nM and represents a novel class of reversible, highly potent and non-peptidic calpain inhibitors.

Tandem chain extension-homoenolate formation: the formation of alpha-methylated-gamma-keto esters

A tandem chain extension-homoenolate formation reaction is described. The treatment of beta-keto esters with the Furukawa reagent followed by exposure to a catalytic amount of trimethylsilyl chloride provides access to an ester homoenolate. Reaction: see text.

New synthetic technology for efficient construction of alpha-hydroxy-beta-amino amides via the Passerini reaction

[reaction: see text] The Passerini reaction of N-protected amino aldehydes, isonitriles, and TFA using pyridine-type bases proceeds under mild conditions and directly affords alpha-hydroxy-beta-amino amide derivatives in moderate to high yields. These adducts are readily hydrolyzed to alpha-hydroxy-beta-amino carboxylic acids. Application of these key intermediates to concise syntheses of P(1)-alpha-ketoamide protease inhibitors is illustrated.

Prebiotic transamination

Biological amino acids and alpha keto acids directly condense with decarboxylation and transamination to yield product amino acids. This process is closely related to unusual amino acid decarboxylase enzymes in certain microorganisms and may represent a primordial mode of amino acid metabolism.

[A substitute treatment for dialysis?]

One of the major problems regarding the administration of amino acids by intravenous feeding is the use of racemic mixtures that are forbidden by the pharmacological regulations; other current problems is the high cost of obtaining pure amino acids. Because of this, our group has been working in the obtention of L-amino acids (assimilables by living organisms) and ketoacids (used by the body as precursors of racemic amino acid mixtures) in a less expensive and simpler way, with the aim of using these products for different pathologies.

Peptide alpha-keto ester, alpha-keto amide, and alpha-keto acid inhibitors of calpains and other cysteine proteases

A series of dipeptidyl and tripeptidyl alpha-keto esters, alpha-keto amides, and alpha-keto acids having leucine in the P2 position were synthesized and evaluated as inhibitors for the cysteine proteases calpain I, calpain II, cathepsin B, and papain. In general, peptidyl alpha-keto acids were more inhibitory toward calpain I and II than alpha-keto amides, which in turn were more effective than alpha-keto esters. In the series Z-Leu-AA-COOEt, the inhibitory potency decreased in the order: Met (lowest KI) > Nva > Phe > 4-Cl-Phe > Abu > Nle (highest KI) with calpain I, while almost the reverse order was observed for calpain II. Extending the dipeptide alpha-keto ester to a tripeptide alpha-keto ester yielded significant enhancement in the inhibitory potency toward cathepsin B, but smaller changes toward the calpains. Changing the ester group in the alpha-keto esters did not substantially decrease KI values for calpain I and calpain II. N-Monosubstituted alpha-keto amides were better inhibitors than the corresponding alpha-keto esters. alpha-Keto amides with hydrophobic alkyl groups or alkyl groups with an attached phenyl group had the lower KI values. N,N-Disubstituted alpha-keto amides were much less potent inhibitors than the corresponding N-monosubstituted peptide alpha-keto amides. The peptide alpha-keto acid Z-Leu-Phe-COOH was the best inhibitor for calpain I (KI = 0.0085 microM) and calpain II (KI = 0.0057 microM) discovered in this study. It is likely that the inhibitors are transition-state analogs and form tetrahedral adducts with the active site cysteine of cysteine proteases and form hydrogen bonds with the active site histidine and possibly another hydrogen bond donor in the case of monosubstituted amides. Several inhibitors prevented spectrin degradation in a platelet membrane permeability assay and may be useful for the treatment of diseases which involve neurodegeneration.

Synthesis and pharmacological evaluation of a new class of 2-oxo-8-azaspiro (4,5)decan-1-ones as analogues of the muscarinic agonist RS-86

A new series of 8-substituted-2-oxo-8-azaspiro (4,5)decan-1-ones has been synthesized and compounds tested for their cholinergic properties in comparison with the muscarinic agonist RS-86. Preliminary in vitro and in vivo pharmacological data indicate that none of them is provided with significant cholinergic effects either at central or peripheral level. A possible explanation for the lack of activity is given on the basis of conformational studies.

New steroid haptens for radioimmunoassay: synthesis of steroids substituted with thioether or ester linkages at the 2 alpha-position

Haptens with bridge at the 2-position have not yet been explored. Radioimmunoassays with antibodies directed against 2 alpha-alkyl bridged steroid haptens are expected to be highly specific due to greater topographical exposure and similarity in conformation to the native steroid. The 2 alpha-alkyl bridged haptens were synthesized by first adding a cyclopropane ring to 2-methylene-4-en-3-one. Selective opening of the three-membered ring with trimethyl silyl iodide and transformation of the iodo group gave a carbocyclic acid, the desired analog for conjugation with protein.

[Production of hydroxy and oxo fatty acids by microorganisms as a model of adipocere formation]

Microbial synthesis of hydroxy and oxo fatty acids was studied as one of the model of experimental adipocere formation. Conversion of various fatty acids into 10-hydroxy and 10-oxo fatty acids by Micrococcus luteus was also studied. Fatty acids possessing cis-9-unsaturated forms were converted into 10-hydroxy and 10-oxo fatty acids. On the other hand, enoic acids possessing trans-9-unsaturated form or the ones which do not have double bond at the 9 -carbon position were inactive as substrates. 10-Hydroxypalmitic and 10-hydroxystearic acids were converted into the corresponding 10-oxo fatty acids but the 10-oxo fatty acids were inactive as substrates. To study the mechanism of the formation of 10-hydroxy and 10-oxo fatty acids, the crude enzyme preparation from Flavobacterium meningosepticum solubilized by sonication was used. The mechanism of hydration and dehydrogenation was proved by gas chromatography-mass spectrometry of 10-hydroxy and 10-oxo fatty acids produced from oleic acid in the presence of D2O or H218O. These results indicate that oleic acid is hydrated to 10-hydroxystearic acid at first and then, the latter compound is dehydrogenated to 10-oxostearic acid.

[Studies on anti-allergic agent. I. 1,2,3-trisubstituted-2-propen-1-one derivatives, 3,4-disubstituted-4-oxo-2-butenoic acids and the related compounds]

A new series of 1,2,3-trisubstituted-2-propen-1-one derivatives (9a-v, 10a-j, 13a-c, 14a-j) and 3,4-disubstituted-4-oxo-2-butenoic acids (6a-i, 7a-n) with azole compounds were synthesized. Inhibitory activities against rat passive cutaneous anaphylaxis (PCA) reaction and histamine release from rat mast cells were tested. The ester derivatives (7a-n, 14a-j) exhibited a more potent inhibitory activity against histamine release compared with alkylamine (9a-v), beta-hydroxyethoxy (10a-j) and carboxylic acid (6a-i, 13a-c) derivatives, but somewhat weaker in their anti-PCA activity. Structure-activity relationships were discussed.

Synthesis and biological evaluation of a monocyclic, fully functional analogue of compactin

Compound 8, a monocyclic analogue of compactin, has been prepared and its efficacy as an inhibitor of 3-hydroxy-3-methylglutarylcoenzyme A reductase (HMGR) evaluated. The synthesis (Schemes I and II) requires seven steps starting with di-(-)-menthyl fumarate and employs the useful RR-phosphonate reagent 14 to attach the mevinic acid side chain to aldehyde 13. A molecular mechanics study shows that the preferred conformations of 18 (a model for compactin) and 19 (a model for 8) are nearly identical. Compound 8 inhibits HMGR with IC50 = 320 microM, compared to a corresponding value of 32 nM for the compactin ketone, 5. The factor of 10,000 difference in the two inhibitors corresponds to a difference in binding energy of 5.45 kcal mol-1, or 1.36 kcal mol-1 for each of the four carbons of 5 that are missing in analogue 8. This quantitative difference is consistent with the idea that the decalin moiety of the mevinic acids play a purely hydrophobic role in binding the inhibitors to the enzyme.