Design, synthesis, and biological evaluation of novel tricyclic HIV-1 integrase inhibitors by modification of its pyridine ring

Recent Developments in the Synthesis of HIV-1 Integrase Strand Transfer Inhibitors Incorporating Pyridine Moiety

Human immunodeficiency virus (HIV) causes one of the most dangerous diseases-acquired immunodeficiency syndrome (AIDS). An estimated about 40 million people are currently living with HIV worldwide, most of whom are already on antiretroviral therapy. This makes the development of effective drugs to combat this virus very relevant. Currently, one of the dynamically developing areas of organic and medicinal chemistry is the synthesis and identification of new compounds capable of inhibiting HIV-1 integrase-one of the HIV enzymes. A significant number of studies on this topic are published annually. Many compounds inhibiting integrase incorporate pyridine core. Therefore, this review is an analysis of the literature on the methods for the synthesis of pyridine-containing HIV-1 integrase inhibitors since 2003 to the present.

Quinolines and isoquinolines as HIV-1 inhibitors: Chemical structures, action targets, and biological activities

Human immunodeficiency virus type 1 (HIV-1), a lentivirus that causes acquired immunodeficiency syndrome (AIDS), poses a serious threat to global public health. Since the advent of the first drug zidovudine, a number of anti-HIV agents acting on different targets have been approved to combat HIV/AIDS. Among the abundant heterocyclic families, quinoline and isoquinoline moieties are recognized as promising scaffolds for HIV inhibition. This review intends to highlight the advances in diverse chemical structures and abundant biological activity of quinolines and isoquinolines as anti-HIV agents acting on different targets, which aims to provide useful references and inspirations to design and develop novel HIV inhibitors for medicinal chemists.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

Heterocycles of synthetic and natural origin are a well-established class of compounds representing a broad range of organic molecules that constitute over 60% of drugs and agrochemicals in the market or research pipeline. Considering the vast abundance of these structural motifs, the development of chemical processes providing easy access to novel complex target molecules by introducing environmentally benign conditions with the main focus on improving the cost-effectiveness of the chemical transformation is highly demanding and challenging. Accordingly, sonochemistry appears to be an excellent alternative and a highly feasible environmentally benign energy input that has recently received considerable and steadily increasing interest in organic synthesis. However, the involvement of transition-metal-catalyst(s) in a chemical process often triggers an unintended impact on the greenness or sustainability of the transformation. Consequently, enormous efforts have been devoted to developing metal-free routes for assembling various heterocycles of medicinal interest, particularly under ultrasound irradiation. The present review article aims to demonstrate a brief overview of the current progress accomplished in the ultrasound-assisted synthesis of pharmaceutically relevant diverse heterocycles using transition-metal-free catalysis.

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

Great progress has been made in the tandem annulation of enynes in the past few years. This review only presents the corresponding reactions of 1,3-enyne structural motifs to provide the functionalized pyridine and pyrrole derivatives. The functionalization reactions cover iodination, bromination, trifluoromethylation, azidation, carbonylation, arylation, alkylation, selenylation, sulfenylation, amidation, esterification, and hydroxylation. We also briefly introduce the applications of the products and the reaction mechanisms for the synthesis of corresponding N-heterocycles.

A Review on Quinoline Derived Scaffolds as Anti-HIV Agents

After restricting the proliferation of CD4+T cells, Human Immunodeficiency Virus (HIV), infection persists at a very fast rate causing Acquired Immunodeficiency Syndrome (AIDS). This demands the vigorous need of suitable anti-HIV agents, as existing medicines do not provide a complete cure and exhibit drawbacks like toxicities, drug resistance, side-effects, etc. Even the introduction of Highly Active Antiretroviral Therapy (HAART) failed to combat HIV/AIDS completely. The major breakthrough in anti-HIV discovery was marked with the discovery of raltegravir in 2007, the first integrase (IN) inhibitor. Thereafter, the discovery of elvitegravir, a quinolone derivative emerged as the potent HIV-IN inhibitor. Though many more classes of different drugs that act as anti-HIV have been identified, some of which are under clinical trials, but the recent serious focus is still laid on quinoline and its analogues. In this review, we have covered all the quinoline-based derivatives that inhibit various targets and are potential anti-HIV agents in various phases of the drug discovery.

Pyrroloaryls and pyrroloheteroaryls: Inhibitors of the HIV fusion/attachment, reverse transcriptase and integrase

Heterocyclic compounds execute a very important role in drug design and discovery. This article provides the basic milestones of the research for pyrroloaryl and pyrroloheteroaryl based components targeting HIV viral replication cycle. Anti-HIV activity is elaborated for several classes of pyrrolo-compounds as pyrrolopyridines, pyrrolopyrimidines, pyrrolopyridazines, pyrrolobenzodiazepinones, pyrrolobenzothiazepines, pyrrolobenzoxazepinones, pyrrolophenanthridines, pyrroloquinoxalines, pyrrolotriazines, pyrroloquinolines, pyrrolopyrazinones, pyrrolothiatriazines, arylthiopyrroles and pyrrolopyrazolones targeting two essential HIV enzymes, reverse transcriptase and integrase as well as attachment/fusion of HIV virons to the host CD-4 cell. Such attempts were resulted in a discovery of highly potent anti-HIV agents suitable for clinical trials, for example, BMS-378806, BMS-585248, BMS-626529, BMS-663068, BMS-488043 and BMS-663749, etc. as anti-HIV attachment agents, triciribine, QX432, BI-1 and BI-2 as HIV RT inhibitors which are in preclinical or clinical development. Mechanism of action of compounds presented in this article towards the suppression of HIV attachment/fusion as well as against the activities of HIV enzymes reverse transcriptase and integrase has been discussed. Relationships of new compounds' molecular framework and HIV viral target has been overviewed in order to facilitate further construction of promising anti-HIV agents in future drug discovery process.

Design and synthesis of N-methylpyrimidone derivatives as HIV-1 integrase inhibitors

A series of novel β-diketo derivatives which combined the virtues of dihydroxypyrimidine carboxamide derived from the evolution of DKA and polyhydroxylated aromatics moieties, were designed and synthesized as potential HIV-1 integrase (IN) inhibitors and evaluated their inhibition to the strand transfer process of HIV-1 integrase and anti-HIV-1 activity. The result indicates that 3,4,5-trihydroxylated aromatic derivatives exhibit good inhibition to HIV-1 integrase, but dihydroxylated aromatic derivatives appear little inhibition to HIV-1 integrase. In addition, the preliminary structure-activity relationship (SAR) of these new derivatives was rationalized by docking studies.

Targeting HIV-1 integrase with strand transfer inhibitors

HIV-1 integrase (IN) is a retroviral enzyme essential for integration of genetic material into the DNA of the host cell and hence for viral replication. The absence of an equivalent enzyme in humans makes IN an interesting target for anti-HIV drug design. This review briefly overviews the structural and functional properties of HIV-1 IN. We analyze the binding modes of the established drugs, clinical candidates and a comprehensive library of leads based on innovative chemical scaffolds of HIV-1 IN strand transfer inhibitors (INSTIs). Computational clustering techniques are applied for identifying structural features relating to bioactivity. From bio- and chemo-informatics analyses, we provide novel insights into structure-activity relationships of INSTIs and elaborate new strategies for design of innovative inhibitors.

Crystal structure of 2-[12-methyl-14-phenyl-10,13,14,16-tetra-aza-tetra-cyclo[7.7.0.0(2,7).0(11,15)]hexa-deca-1(16),2,4,6,9,11(15),12-heptaen-8-yl-idene]propandi-nitrile

In the title mol-ecule, C22H12N6, the fused tetracyclic core shows a small lengthwise twist as indicated by the dihedral of 2.7 (2)° between the outer rings. In the crystal, mol-ecules stack along the b-axis direction via offset π-stacking [centroid-centroid distances = 3.5282 (13) and 3.5597 (14) Å] with the stacks weakly associated through C-H⋯N hydrogen bonds. The phenyl ring is rotationally disordered over two orientations with an occupancy ratio of 0.516 (4):0.484 (4).

Inhibiting the HIV integration process: past, present, and the future

HIV integrase (IN) catalyzes the insertion into the genome of the infected human cell of viral DNA produced by the retrotranscription process. The discovery of raltegravir validated the existence of the IN, which is a new target in the field of anti-HIV drug research. The mechanism of catalysis of IN is depicted, and the characteristics of the inhibitors of the catalytic site of this viral enzyme are reported. The role played by the resistance is elucidated, as well as the possibility of bypassing this problem. New approaches to block the integration process are depicted as future perspectives, such as development of allosteric IN inhibitors, dual inhibitors targeting both IN and other enzymes, inhibitors of enzymes that activate IN, activators of IN activity, as well as a gene therapy approach.

A new and efficient method for the synthesis of 3,4-disubstituted pyrrolidine-2,5-diones

A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxy-pyrrolidine-2,5-diones from 3-substituted coumarins and nitromethane has been elaborated. The reaction involved a simple and convenient experimental procedure. The applicability of the rearrangement reaction is determined.

Authentic HIV-1 integrase inhibitors

HIV-1 integrase (IN) is indispensable for HIV-1 replication and has become a validated target for developing anti-AIDS agents. In two decades of development of IN inhibition-based anti-HIV therapeutics, a significant number of compounds were identified as IN inhibitors, but only some of them showed antiviral activity. This article reviews a number of patented HIV-1 IN inhibitors, especially those that possess high selectivity for the strand transfer reaction. These compounds generally have a polar coplanar moiety, which is assumed to chelate two magnesium ions in the binding site. Resistance to those compounds, when given to patients, can develop as a result of IN mutations. We refer to those compounds as authentic IN inhibitors. Continued drug development has so far delivered one authentic IN inhibitor to the market (raltegravir in 2007). Current and future attention will be focused on the development of novel authentic IN inhibitors with the goal of overcoming viral resistance.

tert-Butyl 4-formyl-1H-imidazole-1-carboxyl-ate

In the crystal structure of the title compound, C(9)H(12)N(2)O(3), weak inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into chains. Further weak C-H⋯O hydrogen bonds together with π-π inter-actions [centroid-centroid distance = 3.672 (4) Å] between neighbouring chains lead to a double-chain structure propagating in [100].

Analysis of binding parameters of HIV-1 integrase inhibitors: correlates of drug inhibition and resistance

This study undertook an exploratory data analysis of the binding parameters of HIV-1 integrase inhibitors. The study group involved inhibitors in preclinical development from the diketo acid, pyrroloquinoline and naphthyridine carboxamide families and the most advanced inhibitors Raltegravir and Elvitegravir. Distinct differences were observed in the energetics of binding between the studied classes of inhibitors that also correlated with drug resistant patterns. Quantitative-property-activity-relationships correlated experimental IC(50) values to the binding energy and the logarithm of the partition coefficient between n-octanol and water (clogP). The approach followed here serves as an improved basis for the development of 'second generation' integrase inhibitors.

Preclinical evaluation of GS-9160, a novel inhibitor of human immunodeficiency virus type 1 integrase

GS-9160 is a novel and potent inhibitor of human immunodeficiency virus type 1 (HIV-1) integrase (IN) that specifically targets the process of strand transfer. It is an authentic inhibitor of HIV-1 integration, since treatment of infected cells results in an elevation of two-long terminal repeat circles and a decrease of integration junctions. GS-9160 has potent and selective antiviral activity in primary human T lymphocytes producing a 50% effective concentration (EC(50)) of approximately 2 nM, with a selectivity index (50% cytotoxic concentration/EC(50)) of approximately 2,000. The antiviral potency of GS-9160 decreased by 6- to 10-fold in the presence of human serum. The antiviral activity of GS-9160 is synergistic in combination with representatives from three different classes of antiviral drugs, namely HIV-1 protease inhibitors, nonnucleoside reverse transcriptase inhibitors, and nucleotide reverse transcriptase inhibitors. Viral resistance selections performed with GS-9160 yielded a novel pattern of mutations within the catalytic core domain of IN; E92V emerged initially, followed by L74M. While E92V as a single mutant conferred 12-fold resistance against GS-9160, L74M had no effect as a single mutant. Together, these mutations conferred 67-fold resistance to GS-9160, indicating that L74M may potentiate the resistance caused by E92V. The pharmacokinetic profile of GS-9160 in healthy human volunteers revealed that once-daily dosing was not likely to achieve antiviral efficacy; hence, the clinical development of this compound was discontinued.

HIV-1 integrase inhibitors: 2005-2006 update

HIV-1 integrase (IN) catalyzes the integration of proviral DNA into the host genome, an essential step for viral replication. Inhibition of IN catalytic activity provides an attractive strategy for antiretroviral drug design. Currently two IN inhibitors, MK-0518 and GS-9137, are in advanced stages of human clinical trials. The IN inhibitors in clinical evaluation demonstrate excellent antiretroviral efficacy alone or in combination regimens as compared to previously used clinical antiretroviral agents in naive and treatment-experienced HIV-1 infected patients. However, the emergence of viral strains resistant to clinically studied IN inhibitors and the dynamic nature of the HIV-1 genome demand a continued effort toward the discovery of novel inhibitors to keep a therapeutic advantage over the virus. Continued efforts in the field have resulted in the discovery of compounds from diverse chemical classes. In this review, we provide a comprehensive report of all IN inhibitors discovered in the years 2005 and 2006.

Tricyclic HIV integrase inhibitors: potent and orally bioavailable C5-aza analogs

A series of C5-aza tricyclic HIV integrase inhibitors was prepared. A highly potent and orally bioavailable compound (compound 9) was identified and selected for development.

The chloroxoquinolinic derivative 6-chloro-1,4-dihydro-4-oxo-1-(β-D-ribofuranosyl) quinoline-3-carboxylic acid inhibits HSV-1 adsorption by impairing its adsorption on HVEM

In this paper, we describe that the oxoquinolinic acid derivative (compound A) inhibited HSV-1 adsorption on Vero cells. This effect was achieved with an EC(50) value of 10 +/- 2.0 microM and with low cytotoxicity, since the CC(50) value for compound A was >1000 microM. Moreover, we demonstrate for the first time that adsorption inhibition was due to the blockage of the interactions between HSV-1 and the cellular receptor herpes virus entry mediator (HVEM). These results show that compound A can prevent HSV-1 infection in Vero cells, encouraging further studies to determine at what level compound A inhibits HSV-1-HVEM interactions.

A peptide with HIV-1 reverse transcriptase inhibitory activity from the medicinal mushroom Russula paludosa

Hot water extracts of 16 species of mushrooms, including both edible and medicinal mushrooms, were screened for human immunodeficiency virus (HIV)-1 reverse transcriptase (RT) inhibitory activity. Extracts of Lactarius camphoratus, Trametes suaveolens, Sparassis crispa, Pleurotus sajor-caju, Pleurotus pulmonarius, and Russula paludosa elicited over 50% inhibition when tested at the concentration of 1 mg/ml. The extract of R. paludosa demonstrated the highest inhibitory activity on HIV-1 RT (97.6%). Fraction SU2, purified from R. paludosa extract by anion exchange chromatography on DEAE-cellulose and gel filtration on Superdex 75, exhibited potent inhibitory activity on HIV-1 RT. At the concentrations of 1 mg/ml, 0.2 mg/ml, and 0.04 mg/ml, the inhibition ratios were 99.2%, 89.3%, and 41.8%, respectively, giving an IC50 of 11 microM. The molecular mass of SU2 was 4.5 kDa and its N-terminal amino acid sequence was determined to be KREHGQHCEF. The peptide was devoid of hemagglutinating, ribonuclease, antifungal, protease, protease inhibitory, and laccase activities.