Potent HIV-1 Protease Inhibitors Research Articles

Synthesis of cyclic peptides as mimics for the constrained conformation of structural analogues of HIV protease inhibitors

A γ-turn induced cyclisation of tripeptides 4 can be performed in a ring-closing metathesis reaction using Grubb's catalyst to the corresponding cyclic peptides 5 . These cyclic peptides mimic the constrained conformation of structural analogues of potential HIV protease inhibitors.

A Study on Docking Mode of HIV Protease and Their Inhibitors.

The capability to propose feasible ways of binding a putative ligand inhibitor to a known receptor site is crucial to the successful structure-based drug design. A computer docking approach is to position or “dock ligand and receptor molecules together in many different ways and then score each orientation by applying a reasonable evaluation function. AutoDock3.0 is an unbiased type docking program in which a user does not have to direct a ligand to an active site, but the system finds an optimal position after a ligand is placed in a random manner. Synthesized derivatives of the intact inhibitor (inh1) of HIV protease were investigated for their docking modes as compared with their Ki values. Among the derivatives, inh3trans and inh6H were found to be more powerful inhibitors of HIV protease than the others. Gibbs free energy calculated by applying molecular mechanics interaction energies was compared with the one obtained by using experimental inhibitory potencies for a series of HIV protease inhibitors, and a fairly good correlation was found between the two. Based on this favorable correlationship between the computational and the experimental results, the computational experiments were pursued for the compounds drawn by Sybyl taking into consideration the fact that unexploited carbon affinity regions (or hydrophobic regions) with sizable volume were detected on the docking study of inh1 and inh8 against HIV protease. Those were compounds with a t-butyl substituted by various hydrophobic side chains. Among those a compound with a benzyl group exhibited the lowest docking energy. Since one of the goals of this paper was to perform the computational drug-design experiment to investigate potential HIV protease inhibitors, the authors would like to leave the clinical investigational work for the expertise of those areas.

2,5-Anhydro sugar diacid and 2,5-anhydro sugar diamine based C2 symmetric peptidomimetics as potential HIV-1 protease inhibitors

Conformationally constrained molecular frameworks of the 2,5-anhydro sugar diacid ( 9) and 2,5-anhydro sugar diamines ( 10, 11) were used to construct architecturally beautiful novel C 2 symmetric peptidomimetics 1– 8. Although none of these compounds showed any significant HIV-1 protease inhibitory activity, further refinements in design may lead to protease inhibitors based on these rigid carbohydrate-derived scaffolds.

Fast microwave-assisted preparation of aryl and vinyl nitriles and the corresponding tetrazoles from organo-halides

Aryl and vinyl nitriles have been prepared in very high yields from the corresponding bromides using palladium-catalyzed reactions with microwave irradiation employed as the energy source. Furthermore, flash heating was used successfully for the conversion of these nitriles into aryl and vinyl tetrazoles by cycloaddition reactions. One-pot transformation of aryl halides directly to the aryl tetrazoles could be accomplished both in solution and on solid support. All reactions were completed in minutes rather than in hours or days as previously reported with the standard thermal heating technique. A very potent HIV-1 protease inhibitor (K(i) = 0. 56 nM), comprising two tetrazole heterocycles as carboxyl group bioisosteres, was prepared in one pot by microwave-promoted cyanation of a bromo precursor and a subsequent cycloaddition reaction. The temperature-time profiles at 13, 20, and 60 W magnetron input power in DMF are presented.

Use of proline bioisosteres in potential HIV protease inhibitors: phenylalanine-2-thiophenoxy-3-pyrrolidinone: synthesis and anti-HIV evaluation

The synthesis of new phenylalanine-2-thiophenoxy-3-pyrrolidinones is described. Anti-HIV recombinant protease assays and HIV infected cell culture assays (observation of syncytia) demonstrated the potent anti-HIV activity of this new class of pseudopeptides.

Solid phase assisted synthesis of HIV-1 protease inhibitors. Expedient entry to unsymmetrical substitution of aC2symmetric template

A solid phase synthesis has been developed leading up to unsymmetrical HIV-1 protease inhibitors that are not readily available by conventional solution phase chemistry (18a–g). To prepare these compounds the hydroxyl group of (1S,2R)-(–)-cis-1-phthalimido-2-indanol (3) was coupled to a Merrifield resin via a dihydropyrane linker. Cleavage of the phthalimido protecting group and reaction of the liberated amine with the bis-activated symmetrical diacid 15 resulted in the resin bound amide 16. Coupling of 16 with amino acids and amines followed by hydrolysis produced the desired unsymmetrical products 18a–g from which potent HIV-1 protease inhibitors were identified, e.g., 18e (ki= 0.1 nM), 18a (ki= 0.2 nM) and 18c (ki= 2 nM).Key words: HIV, inhibitor, protease, solid phase.

(1S)-1-[(4R)-2,2-dimethyl-1,3-dioxolan+-4-yl][-2-hydroxyethylamm onium benzoate, a versatile building block for chiral 2-aminoalkanols: concise synthesis and application to nelfinavir, a potent HIV-protease inhibitor.

A concise synthesis of a versatile chiral C4 building block for 2-aminoalkanols, (1S)-1-[(4R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-hydroxyethylammo nium benzoate (1a), was described. 1 (1a and its enantiomer 1b) acted as four stereoisomers of optically active 2-amino-1,3,4-butanetriol. The versatility of 1 was demonstrated by its application to the practical synthesis of nelfinavir (2), a potent HIV-protease inhibitor, as well as by the stereospecific synthesis of three diastereomers of 2.

5,6-Dihydropyran-2-ones possessing various sulfonyl functionalities: potent nonpeptidic inhibitors of HIV protease.

On the basis of previous SAR findings and molecular modeling studies, a series of compounds were synthesized which possessed various sulfonyl moieties substituted at the 4-position of the C-3 phenyl ring substituent of the dihydropyran-2-one ring system. The sulfonyl substituents were added in an attempt to fill the additional S(3)' pocket and thereby produce increasingly potent inhibitors of the target enzyme. Racemic and enantiomerically resolved varieties of selected compounds were synthesized. All analogues in the study displayed decent binding affinity to HIV protease, and several compounds were shown to possess very good antiviral efficacy and safety margins. X-ray crystallographic structures confirmed that the sulfonamide and sulfonate moieties were filling the S(3)' pocket of the enzyme. However, the additional substituent did not provide improved enzymatic inhibitory or antiviral activity as compared to the resolved unsubstituted aniline. The addition of the sulfonyl moiety substitution does not appear to provide favorable pharamacokinectic parameters. Selected inhibitors were tested for antiviral activity in clinical isolates and exhibited similar antiviral activity against all of the HIV-1 strains tested as they did against the wild-type HIV-1. In addition, the inhibitors exhibited good antiviral efficacies against HIV-1 strains that displayed resistance to the currently marketed protease inhibitors.

Synthesis of N-Alkyl-(α-Aminoalkyl)Phosphine Oxides and Phosphonic Esters as Potential HIV-Protease Inhibitors, Starting fromα-Aminoacids

The synthesis of α-aminophosphonic acid derivatives starting from α-aminoacids is described. These phosphorus peptide mimics could be potential HIV-protease inhibitors.

Structure-activity relationship of orally potent tripeptide-based HIV protease inhibitors containing hydroxymethylcarbonyl isostere.

We designed and synthesized a new class of peptidomimetic human immunodeficiency virus protease inhibitors containing a unique unnatural amino acid, allophenylnorstatine [Apns; (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], with a hydroxymethylcarbonyl isostere as the active moiety. From a structure-activity relationship study of HIV-1 protease inhibition, enzyme selectivity for other aspartyl proteases, the antiviral activity and pharmacokinetics in rats, 24c (KNI-227) and 24d (KNI-272, our first clinical candidate) were found to be selective and orally potent HIV protease inhibitors. Moreover, an improvement of the pharmacokinetic features of KNI-272 provided two long-lasting and highly bioavailable compounds (24g: JE-2178, 24h: JE-2179).

Determination of nelfinavir, a potent HIV protease inhibitor, and its active metabolite M8 in human plasma by high-performance liquid chromatography with photodiode-array detection

We developed and characterized a high-performance liquid chromatographic assay for the determination of nelfinavir (NFV), a potent HIV protease inhibitor, and its active metabolite M8 in human plasma. Extraction of the internal standard, M8 and NFV from the plasma buffered at pH 9.5 was achieved by a liquid–liquid extraction with a mixture of methyl- tert.-butyl ether and hexane. Following two washes of the reconstituted sample with hexane, separation was achieved on an octadecylsilyl analytical column with a mobile phase containing 0.1% trifluoroacetic acid–acetonitrile–methanol (51:46:5, v/v). Detection was performed using an ultraviolet photodiode-array detector. The signal was monitored at a wavelength of 220 nm. The assay was found to be linear and has been validated over the concentration range of 25 to 3000 μg/l for M8 and 25 to 6000 μg/l for NFV, from 500 μl of plasma. Recoveries were 98.9% (SD 8.9%), and 100.2% (SD 11.7%) for M8 and NFV, respectively. Concentrations that gave a signal-to-noise ratio of three (15 μg/l for both M8 and NFV) were selected to determine the limit of detection. The lower limit of quantification (25 μg/l for both M8 and NFV) was defined as the concentration for which the relative standard deviation and the percent deviation from the nominal concentration were lower than 20%.

Asymmetric Synthesis of 1,2,3,4,5,6-Hexahydro-5-hydroxypyrimidin-2-ones as Potential HIV-Protease Inhibitors

Asymmetric Synthesis of 1,2,3,4,5,6-Hexahydro-5-hydroxypyrimidin-2-ones as Potential HIV-Protease Inhibitors

Determination of indinavir in plasma by solid-phase extraction and column liquid chromatography.

Indinavir is a specific and potent HIV protease inhibitor. A new column liquid chromatographic method for the determination of this drug is described. This assay was developed for the clinical monitoring of trough concentrations in AIDS patients, using a 1-mL plasma sample volume. Determination of indinavir was made by a rapid solid-phase extraction procedure with the new polymeric Oasis HLB sorbent followed by a reversed-phase liquid chromatography and a UV detection at 210 nm. A weighted least squares linear regression (weighting factor = 1/y where y = peak height ratio) was used to calculate the equation relating the peak-height ratio of the drug and the internal standard to the concentration of indinavir in the range 10-800 ng/mL (0.014-1.124 microM). At the lower limit of quantification (10 ng/mL), the mean accuracy was 102 +/- 7% and 104 +/- 11% for within- and between-day analysis, respectively. The limit of detection, based on a signal-to-noise ratio of 2:1, was 4 ng/mL (0.006 microM). Compounds of interest were eluted from the extraction cartridges with 300 microL of mobile phase, and mean absolute recoveries of indinavir and internal standard were 66.4% and 80.3%, respectively. No metabolite of indinavir was found to co-elute with the drug or its internal standard. Among the tested drugs, especially nucleoside analogues and the other protease inhibitors used in clinical care, none was found to interfere with the assay at this time. This simple and selective method is suitable for therapeutic indinavir monitoring.

4-Hydroxy-5,6-Dihydro-2 H-pyran-2-ones. 3. Bicyclic and hetero-aromatic ring systems as 3-position scaffolds to bind to S 1′ and S 2′ of the HIV-1 protease enzyme

5,6-Dihydro-2 H-pyran-2-ones are potent inhibitors of HIV-1 protease, which bind to the S 1, S 2, S 1′, and S 2′ pockets and have a unique binding mode with the catalytic aspartyl groups and the flap region of the enzyme. Efforts to explore 3-position heterocyclic scaffolds that bind to the S 1′ and S 2′ pockets have provided a number of selected analogs that display high HIV-1 protease inhibitory activity.

Potent HIV protease inhibitors containing a novel (2-phenylsulfanyl-1-hydroxyethyl)amide isostere

Based on the concept of bioisosterism, we report the design and synthesis of new protease inhibitors. These new compounds incorporate in their backbone the synthon 2-N-Acyl-2-Phenylsulfanyl-1-Hydroxyethyl (I) which confers on the resulting compounds both in vitro activity on MT 4 infected cells and HIV-1 protease inhibition properties.

ChemInform Abstract: Design and Synthesis of New Potent C2‐Symmetric HIV‐1 Protease Inhibitors. Use of L‐Mannaric Acid as a Peptidomimetic Scaffold.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Computational Study of KNI-272, a Potent Inhibitor of HIV-1 Protease: On the Mechanism of Preorganization

The compound KNI-272 is a potent, peptide-like inhibitor of HIV protease. Its conformation when complexed with the protease is close to that which it assumes in its single-molecule crystal. This observation led to the suggestion that KNI-272 gains affinity by being preorganized for binding. On the other hand, one might well expect KNI-272 to be flexible because it possesses 15 rotatable bonds. Moreover, a recent ab initio study of KNI-272 suggests that it is not preorganized because its bound conformation is strained. Here, we use a novel algorithm to study the conformational distribution of this inhibitor. The results show good agreement with a recent NMR analysis of KNI-272 in solution. The calculations indicate that KNI-272 in solution occupies three major conformations, one of which matches the bound conformation and the NMR structure. In addition, the thioproline amide bond tends to be in the trans conformation found in the complex of KNI-272 with HIV protease. Further calculations on hypothetical an...

Comparison of azacyclic urea A-98881 as HIV-1 protease inhibitor with cage dimeric N-benzyl 4-(4-methoxyphenyl)-1,4-dihydropyridine as representative of a novel class of HIV-1 protease inhibitors: a molecular modeling study.

The functional groups of cage dimeric N-alkyl substituted 3,5-bis(hydroxymethyl)-4-(4-methoxyphenyl)-1,4-dihydropyridines are similar to those of cyclic and azacyclic ureas that are potent inhibitors of HIV-1 protease of the dihydroxyethylene- and hydroxyethylene type, respectively. In the following study the conformity of common functional groups is investigated concerning their orientation in space as well as in the enzyme HIV-1 protease. Starting from X-ray crystal data of the centrosymmetric cage dimeric N-benzyl derivative with ester groups, the derivative with hydroxymethylene groups was built and a systematic conformational search was performed for the conformationally important torsion angles considering electrostatic and van der Waals interactions. From the huge number of conformations those comprising centrosymmetrical and C2-symmetrical energy minima were selected and minimized. The three remaining conformers were fitted to the azacyclic urea A-98881 selected from the HIV-1 protease enzyme-inhibitor complex using the centroids of the corresponding aromatic residues and additionally by the field fit option of the Advanced CoMFA module of SYBYL. Interestingly, the energetically most favourable one, which, additionally, possesses C2-symmetry like the active site cavity of HIV-1 protease, showed the best fit. Comparing the electrostatic potential (EP) of the latter with the EP of A-98881 the aromatic residues show excellent accordance. Slight differences in the extent of the EP were found in the areas of the hydroxymethylene groups of the cage dimer and the single hydroxy group as well as the urea carbonyl group of A-98881, respectively. In order to compare the binding possibilities to the enzyme HIV-1 protease for the cage dimer and A-98881, their interaction fields with certain probes (CH3 for alkyl, NHamide, and carbonyl, O- of COO-), representing the decisive functional groups of the active site, have been calculated using GRID and projected into the enzyme placing the structures according to the position of A-98881 in the enzyme-inhibitor complex. The strongest calculated fields of the O- probe were found near Asp 25 for both structures. Another respective conformity consists in the overlap of the fields for the NHamide probe near Ile 50 and 50' for the investigated cage dimer and A-98881.

Vitamin E-TPGS increases absorption flux of an HIV protease inhibitor by enhancing its solubility and permeability.

To investigate the effect of vitamin E-TPGS, d-alpha-tocopheryl polyethylene glycol 1000 succinate, on the solubility and permeability of amprenavir, a potent HIV protease inhibitor. The aqueous solubility of amprenavir was measured as a function of vitamin E-TPGS concentration. Directional transport through Caco-2 cell monolayers was determined in the presence and absence of vitamin E-TPGS and P-glycoprotein inhibitors. Absorption flux was estimated from Caco-2 cell permeability and aqueous solubility. The solubility of amprenavir in a pH 7 buffer at 37 degrees C was 0.036+/-0.007 mg/mL. The solubility linearly increased with increasing vitamin E-TPGS concentration (above 0.2 mg/mL). Polarized transport was demonstrated in the basolateral to apical direction, exceeding apical to basolateral transport by a factor of 6. The active efflux system was inhibited by vitamin E-TPGS and known P-glycoprotein inhibitors verapamil and GF120918. The solubility of amprenavir was improved in the presence of vitamin E-TPGS through micelle solubilization. Vitamin E-TPGS inhibits the efflux system and enhances the permeability of amprenavir. Overall, vitamin E-TPGS enhanced the absorption flux of amprenavir by increasing its solubility and permeability. The enhancement is essential to the development of the novel soft gelatin capsule formulation of amprenavir for use in the clinic.

Design and synthesis of novel conformationally restricted HIV protease inhibitors

A set of HIV protease inhibitors represented by compound 2 has previously been described. Structural and conformational analysis of this compound suggested that conformational restriction of the P 1/P 2 portion of the molecule could lead to a novel set of potent protease inhibitors. Thus, probe compounds 3–7 were designed, synthesized, and found to be potent inhibitors of HIV protease.