Synthesis and Biological Evaluation of Pyrazolo[1,5-a]pyrimidine Compounds as Potent and Selective Pim-1 Inhibitors

PIM1 kinase and its diverse substrate in solid tumors

The PIM kinase family, consisting of PIM1, PIM2, and PIM3, is a group of serine/threonine protein kinases crucial for cellular growth, immunoregulation, and oncogenesis. PIM1 kinase is often overexpressed in solid and hematopoietic malignancies, promoting cell survival, proliferation, migration, and senescence by activating key genes. In vitro and in vivo studies have established the oncogenic potential of PIM1 kinases. These kinases have been implicated in tumor progression, metastasis, and resistance to chemotherapy, underscoring their potential as a therapeutic target for cancer therapy. This review delves into the intricate molecular mechanisms through which PIM1 interacts with specific substrates in different tumor tissues, leading to diverse outcomes in various human cancers. Over the past decade, the inhibition of PIM1 in cancers has garnered significant attention as a potential standalone treatment. Various in vitro, in vivo, and early clinical trial data have provided support for this approach to varying extents. Novel compounds that inhibit PIM1 kinase have shown effectiveness and a favorable toxicity profile in preclinical studies. Several of these substances are now being studied in clinical trials due to their promising outcomes. This article provides a thorough examination of the PIM1 kinase pathways and the recent advancements in producing PIM1 kinase inhibitors for the treatment of cancer.

Heterocycle-functional steroidal derivatives: Design, synthesis, bioevaluation and SARs of steroidal pyrazolo[1,5-a]pyrimidines as potential ALK inhibitors

Two series of heterocyclic steroidal pyrazolo[1,5-a]pyrimidines derived from dehydroepiandrosterone (DHEA) and epiandrosterone (EPIA) were designed and synthesized, and these compounds were screened for their potential antiproliferation activities. The preliminary bioassay indicated that some of target compounds exhibited significantly good antiproliferation activities against human melanoma cell line (A875) and human hepatocellular carcinoma (Huh-7) cell lines compared with 5-fluorouracil (5-FU), and some of which present good antiproliferative activities as potential ALK inhibitors. The detailed analysis of structure-activity relationships (SARs) based on the inhibition activities, kinase assay, and molecular docking demonstrated that the antiproliferation activities of these steroidal pyrazolo[1,5-a]pyrimidine might be affected by the β-hydroxyl group of steroidal scaffold and the N atom of pyridine heterocycle. Especially, compound 4c has certain inhibitory effects on the tyrosine protein kinases ALK, CDK2/CyclinE1, FAK, CDK5/P35, CDK9/CyclinT1, CDK5/P25, PIM2, CDK2/CyclinA2, CDK1/CyclinB1, etc., and which displayed highest inhibitory effect on the kinases of ALK with inhibition rate 40.63 % at the concentration of 10 μM, which induced cell death in A875 cells at least partly (initially), by apoptosis.

Visible-Light-Mediated Regioselective C3-H Selenylation of Pyrazolo[1,5-a]pyrimidines Using Erythrosine B as Photocatalyst

A visible-light-induced efficient methodology has been developed for the C-H selenylation of pyrazolo[1,5-a]pyrimidine derivatives employing erythrosine B as the photocatalyst. This is the first report on the regioselective selenylation of pyrazolo[1,5-a]pyrimidines. The efficiency of this methodology for the selenylation of different electron-rich heterocycles like pyrazole, indole, imidazo[1,2-a]pyridine, imidazo[2,1-b]thiazole, and 4-(phenylamino)-2H-chromen-2-one has been also demonstrated. The exploration of erythrosine B as a photocatalyst with a simple and mild procedure, wide substrate scope, and practical applicability and the employment of eco-friendly energy, oxidant, and solvent are the attractive characteristics of this methodology.

Insights into the medicinal chemistry of heterocycles integrated with a pyrazolo[1,5-a]pyrimidine scaffold

Pyrazolo[1,5-a]pyrimidines are the dominant motif of many drugs; for instance, zaleplon and indiplon are sedative agents and ocinaplon was identified as an anxiolytic agent. The importance of this class of compounds lies in its varied and significant biological activities, and accordingly, considerable methods have been devised to prepare these compounds. Hence, other derivatives of this class of compounds were prepared by substitution reactions with different nucleophiles exploiting the activity of groups linked to the ring carbon and nitrogen atoms. The methods used vary through the condensation reactions of the aminopyrazoles with 1,2-allenic, enaminonitriles, enaminones, 1,3-diketones, unsaturated nitriles, or unsaturated ketones. Alternatively, these compounds are prepared through the reactions of acyclic reagents, as these methods were recently developed efficiently with high yields. The current review highlighted the recent progress of the therapeutic potential of pyrazolo[1,5-a]pyrimidines as antimicrobial, anticancer, antianxiety, anti-proliferative, analgesic, and antioxidant agents, carboxylesterase, translocator protein and PDE10A inhibitors, and selective kinase inhibitors.

Targeting Echinococcus multilocularis PIM kinase for improving anti-parasitic chemotherapy

BACKGROUND

The potentially lethal zoonosis alveolar echinococcosis (AE) is caused by the metacestode larval stage of the tapeworm Echinococcus multilocularis. Current AE treatment options are limited and rely on surgery as well as on chemotherapy involving benzimidazoles (BZ). BZ treatment, however, is mostly parasitostatic only, must be given for prolonged time periods, and is associated with adverse side effects. Novel treatment options are thus urgently needed.

METHODOLOGY/PRINCIPAL FINDINGS

By applying a broad range of kinase inhibitors to E. multilocularis stem cell cultures we identified the proto-oncogene PIM kinase as a promising target for anti-AE chemotherapy. The gene encoding the respective E. multilocularis ortholog, EmPim, was characterized and in situ hybridization assays indicated its expression in parasite stem cells. By yeast two-hybrid assays we demonstrate interaction of EmPim with E. multilocularis CDC25, indicating an involvement of EmPim in parasite cell cycle regulation. Small molecule compounds SGI-1776 and CX-6258, originally found to effectively inhibit human PIM kinases, exhibited detrimental effects on in vitro cultured parasite metacestode vesicles and prevented the formation of mature vesicles from parasite stem cell cultures. To improve compound specificity for EmPim, we applied a high throughput in silico modelling approach, leading to the identification of compound Z196138710. When applied to in vitro cultured metacestode vesicles and parasite cell cultures, Z196138710 proved equally detrimental as SGI-1776 and CX-6258 but displayed significantly reduced toxicity towards human HEK293T and HepG2 cells.

CONCLUSIONS/SIGNIFICANCE

Repurposing of kinase inhibitors initially designed to affect mammalian kinases for helminth disease treatment is often hampered by adverse side effects of respective compounds on human cells. Here we demonstrate the utility of high throughput in silico approaches to design small molecule compounds of higher specificity for parasite cells. We propose EmPim as a promising target for respective approaches towards AE treatment.

Pyrazolopyrimidines as anticancer agents: A review on structural and target-based approaches

Pyrazolopyrimidine scaffold is one of the privileged heterocycles in drug discovery. This scaffold produced numerous biological activities in which anticancer is important one. Previous studies showed its importance in interactions with various receptors such as growth factor receptor, TGFBR2 gene, CDK2/cyclin E and Abl kinase, adenosine receptor, calcium-dependent Protein Kinase, Pim-1 kinase, Potent Janus kinase 2, BTK kinase, P21-activated kinase 1, extracellular signal-regulated kinase 2, histone lysine demethylase and Human Kinesin-5. However, there is a need of numerous studies for the discovery of target based potential compounds. The structure activity relationship studies may help to explore the generation of potential compounds in short time period. Therefore, in the present review we tried to explore the structural aspects of Pyrazolopyrimidine with their structure activity relationship against various targets for the development of potential compounds. The current review is the compilation of significant advances made on Pyrazolopyrimidines reported between 2015 and 2020.

Bicyclic 5-6 Systems: Comprehensive Synthetic Strategies for the Annulations of Pyrazolo[ 1,5-a]pyrimidines

Pyrazolopyrimidines are a privileged class of 5-6 bicyclic systems with three or four nitrogen atoms, including four possible isomeric structures. The significance of this class of compounds is that they can be applied in medical and pharmaceutical fields due to their unlimited biological aptitude, hence it is the basic skeleton of several synthetic drugs. The current review aimed to highlight all the synthetic routes that have been applied to construct the pyrazolo[1,5-a]pyrimidine ring systems up to date. The sections in this study included the synthesis of pyrazolo[1,5- a]pyrimidines by condensation reactions of 5-aminopyrazoles with each of β-diketones, 1,5-diketones, β- ketoaldehydes, α-cyanoaldehydes, β-enaminones, enamines, enaminonitriles, ethers, with unsaturated ketones, unsaturated thiones, unsaturated esters, unsaturated dienones "1,2-allenic", unsaturated aldehydes, unsaturated imines, and unsaturated nitriles. The routes adopted to synthesize this class of heterocyclic compounds were extended for ring construction from acyclic reagents and multicomponent reactions under catalytic or catalyst-free conditions.

Therapeutic targeting of PIM KINASE signaling in cancer therapy: Structural and clinical prospects

BACKGROUND

PIM kinases are well-studied drug targets for cancer, belonging to Serine/Threonine kinases family. They are the downstream target of various signaling pathways, and their up/down-regulation affects various physiological processes. PIM family comprises three isoforms, namely, PIM-1, PIM-2, and PIM-3, on alternative initiation of translation and they have different levels of expression in different types of cancers. Its structure shows a unique ATP-binding site in the hinge region which makes it unique among other kinases.

SCOPE OF REVIEW

PIM kinases are widely reported in hematological malignancies along with prostate and breast cancers. Currently, many drugs are used as inhibitors of PIM kinases. In this review, we highlighted the physiological significance of PIM kinases in the context of disease progression and therapeutic targeting. We comprehensively reviewed the PIM kinases in terms of their expression and regulation of different physiological roles. We further predicted functional partners of PIM kinases to elucidate their role in the cellular physiology of different cancer and mapped their interaction network.

MAJOR CONCLUSIONS

A deeper mechanistic insight into the PIM signaling involved in regulating different cellular processes, including transcription, apoptosis, cell cycle regulation, cell proliferation, cell migration and senescence, is provided. Furthermore, structural features of PIM have been dissected to understand the mechanism of inhibition and subsequent implication of designed inhibitors towards therapeutic management of prostate, breast and other cancers.

GENERAL SIGNIFICANCE

Being a potential drug target for cancer therapy, available drugs and PIM inhibitors at different stages of clinical trials are discussed in detail.

Functional Pyrazolo[1,5-a]pyrimidines: Current Approaches in Synthetic Transformations and Uses As an Antitumor Scaffold

Pyrazolo[1,5-a]pyrimidine (PP) derivatives are an enormous family of N-heterocyclic compounds that possess a high impact in medicinal chemistry and have attracted a great deal of attention in material science recently due to their significant photophysical properties. Consequently, various researchers have developed different synthesis pathways for the preparation and post-functionalization of this functional scaffold. These transformations improve the structural diversity and allow a synergic effect between new synthetic routes and the possible applications of these compounds. This contribution focuses on an overview of the current advances (2015-2021) in the synthesis and functionalization of diverse pyrazolo[1,5-a]pyrimidines. Moreover, the discussion highlights their anticancer potential and enzymatic inhibitory activity, which hopefully could lead to new rational and efficient designs of drugs bearing the pyrazolo[1,5-a]pyrimidine core.

Recent Progress on Anticancer Agents Incorporating Pyrazole Scaffold

The search of new anticancer agents is considered as a dynamic field of medicinal chemistry. In recent years, the synthesis of compounds with anticancer potential has increased and a large number of structurally varied compounds displaying potent anticancer activities have been published. Pyrazole is an important biologically active scaffold that possessed nearly all types of biological activities. The aim of this review is to collate literature work reported by researchers to provide an overview on in vivo and in vitro anticancer activities of pyrazole based derivatives among the diverse biological activities displayed by them and also presents recent efforts made on this heterocyclic moiety regarding anticancer activities. This review has been driven from the increasing number of publications, on this issue, which have been reported in the literature since the ending of the 20th century (from 1995-to date).

Synthesis and Structure-Activity Relationship of Tetra-Substituted Cyclohexyl Diol Inhibitors of Proviral Insertion of Moloney Virus (PIM) Kinases

Overexpression of PIM 1, 2, and 3 kinases is frequently observed in many malignancies. Previously, we discovered a potent and selective pan-PIM kinase inhibitor, compound 2, currently in phase I clinical trials. In this work, we were interested in replacing the amino group on the cyclohexane ring in compound 2 with a hydroxyl group. Structure-based drug design led to cellularly potent but metabolically unstable tetra-substituted cyclohexyl diols. Efforts on the reduction of Log D by introducing polar heterocycles improved metabolic stability. Incorporating fluorine to the tetra-substituted cyclohexyl diol moiety further reduced Log D, resulting in compound 14, a cellularly potent tetra-substituted cyclohexyl diol inhibitor with moderate metabolic stability and good permeability. We also describe the development of efficient and scalable synthetic routes toward synthetically challenging tetra-substituted cyclohexyl diol compounds. In particular, intermediate 36 was identified as a versatile intermediate, enabling a large-scale synthesis of highly substituted cyclohexane derivatives.

Efficient Access to 3,5-Disubstituted 7-(Trifluoromethyl)pyrazolo[1,5-a]pyrimidines Involving SNAr and Suzuki Cross-Coupling Reactions

An efficient and original synthesis of various 3,5-disubstituted 7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidines is reported. A library of compounds diversely substituted in C-3 and C-5 positions was easily prepared from a common starting material, 3-bromo-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-5-one. In C-5 position, a S_NAr type reaction was achieved by first activating the C–O bond of the lactam function with PyBroP (Bromotripyrrolidinophosphonium hexafluorophosphate), followed by the addition of amine or thiol giving monosubstituted derivatives, whereas in C-3 position, arylation was performed via Suzuki–Miyaura cross-coupling using the commercially available aromatic and heteroaromatic boronic acids. Moreover, trifluoromethylated analogues of potent Pim1 kinase inhibitors were designed following our concise synthetic methodology.

A novel protocol for catalyst-free synthesis of fused six-member rings to triazole and pyrazole

Herein, an effectual, quick and novel method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine derivatives. This series of fused six-member rings to triazole and pyrazole was prepared via the catalyst-free reaction of dialkyl acetylenedicarboxylates and 3-substituted 1H-1,2,4-triazole or 3-amino-1H-pyrazole-4-carbonitrile. The structures of the prepared products were deduced from their Fourier-transform infrared, elemental analysis and proton and carbon-13 nuclear magnetic resonance spectral data. A novel and green method is described for the synthesis of new triazolo[1,5-a]pyrimidine, triazolo[5,1-b][1,3] thiazine and pyrazolo[1,5-a]pyrimidine derivatives.

A Kinase Inhibitor with Anti-Pim Kinase Activity is a Potent and Selective Cytotoxic Agent Toward Acute Myeloid Leukemia

More than 40 years ago, the present standard induction therapy for acute myeloid leukemia (AML) was developed. This consists of the metabolic inhibitor cytarabine (AraC) and the cytostatic topoisomerase 2 inhibitor daunorubucin (DNR). In light of the high chance for relapse, as well as the large heterogeneity, novel therapies are needed to improve patient outcome. We have tested the anti-AML activity of 15 novel compounds based on the scaffolds pyrrolo[2,3-a]carbazole-3-carbaldehyde, pyrazolo[3,4-c]carbazole, pyrazolo[4,3-a]phenanthridine, or pyrrolo[2,3-g]indazole. The compounds were inhibitors of Pim kinases, but could also have inhibitory activity against other protein kinases. Ser/Thr kinases like the Pim kinases have been identified as potential drug targets for AML therapy. The compound VS-II-173 induced AML cell death with EC₅₀ below 5 μmol/L, and was 10 times less potent against nonmalignant cells. It perturbed Pim-kinase-mediated AML cell signaling, such as attenuation of Stat5 or MDM2 phosphorylation, and synergized with DNR to induce AML cell death. VS-II-173 induced cell death also in patients with AML blasts, including blast carrying high-risk FLT3-ITD mutations. Mutation of nucleophosmin-1 was associated with good response to VS-II-173. In conclusion new scaffolds for potential AML drugs have been explored. The selective activity toward patient AML blasts and AML cell lines of the pyrazolo-analogue VS-II-173 make it a promising drug candidate to be further tested in preclinical animal models for AML.

Discovery of ( R)-8-(6-Methyl-4-oxo-1,4,5,6-tetrahydropyrrolo[3,4- b]pyrrol-2-yl)-3-(1-methylcyclopropyl)-2-((1-methylcyclopropyl)amino)quinazolin-4(3 H)-one, a Potent and Selective Pim-1/2 Kinase Inhibitor for Hematological Malignancies

Pim kinases are a family of constitutively active serine/threonine kinases that are partially redundant and regulate multiple pathways important for cell growth and survival. In human disease, high expression of the three Pim isoforms has been implicated in the progression of hematopoietic and solid tumor cancers, which suggests that Pim kinase inhibitors could provide patients with therapeutic benefit. Herein, we describe the structure-guided optimization of a series of quinazolinone-pyrrolodihydropyrrolone analogs leading to the identification of potent pan-Pim inhibitor 28 with improved potency, solubility, and drug-like properties. Compound 28 demonstrated on-target Pim activity in an in vivo pharmacodynamic assay with significant inhibition of BAD phosphorylation in KMS-12-BM multiple myeloma tumors for 16 h postdose. In a 2-week mouse xenograft model, daily dosing of compound 28 resulted in 33% tumor regression at 100 mg/kg.

3-Formylpyrazolo[1,5- a]pyrimidines as Key Intermediates for the Preparation of Functional Fluorophores

A one-pot route for the regioselective synthesis of 3-formylpyrazolo[1,5- a]pyrimidines 4a-k in good yields through a microwave-assisted process is provided. The synthesis proceeds via a cyclocondensation reaction between β-enaminones 1 with NH-3-aminopyrazoles 2, followed by formylation with an iminium salt moiety (Vilsmeyer-Haack reagent). These N-heteroaryl aldehydes 4 were successfully used as strategic intermediates for the preparation of novel functional fluorophores with yields up to 98%. The structures of the products obtained and regioselectivity of the reactions were determined on the basis of NMR measurements and X-ray diffraction analysis. Since pyrazolo[1,5- a]pyrimidines (PPs) 3 have shown an important fluorescence, photophysical properties of four 2-methylderivatives substituted at position 7 with different acceptor (A) or donor (D) groups were investigated. The compounds evaluated exhibited large Stokes shift in different solvents, but only the substituted p-methoxyphenyl (4-An) showed a strong fluorescence intensity with quantum yields up to 44% due to its greater ICT. Therefore, hybrid systems based on pyrazolo[1,5- a]pyrimidines could be used as fluorescent probes to detect biologically or environmentally relevant species.

Structure-based design of novel quinoxaline-2-carboxylic acids and analogues as Pim-1 inhibitors

We identified a new series of quinoxaline-2-carboxylic acid derivatives, targeting the human proviral integration site for Moloney murine leukemia virus-1 (HsPim-1) kinase. Seventeen analogues were synthesized providing useful insight into structure-activity relationships studied. Docking studies realized in the ATP pocket of HsPim-1 are consistent with an unclassical binding mode of these inhibitors. The lead compound 1 was able to block HsPim-1 enzymatic activity at nanomolar concentrations (IC₅₀ of 74 nM), with a good selectivity profile against a panel of mammalian protein kinases. In vitro studies on the human chronic myeloid leukemia cell line KU812 showed an antitumor activity at micromolar concentrations. As a result, compound 1 represents a promising lead for the design of novel anticancer targeted therapies.

Predictive Model for Site-Selective Aryl and Heteroaryl C-H Functionalization via Organic Photoredox Catalysis

Direct C-H functionalization of aromatic compounds is a useful synthetic strategy that has garnered much attention because of its application to pharmaceuticals, agrochemicals, and late-stage functionalization reactions on complex molecules. On the basis of previous methods disclosed by our lab, we sought to develop a predictive model for site selectivity and extend this aryl functionalization chemistry to a selected set of heteroaromatic systems commonly used in the pharmaceutical industry. Using electron density calculations, we were able to predict the site selectivity of direct C-H functionalization in a number of heterocycles and identify general trends observed across heterocycle classes.

An insight on synthetic and medicinal aspects of pyrazolo[1,5-a]pyrimidine scaffold

Pyrazolo[1,5-a]pyrimidine scaffold is one of the privileged hetrocycles in drug discovery. Its application as a buliding block for developing drug-like candidates has displayed broad range of medicinal properties such as anticancer, CNS agents, anti-infectious, anti-inflammatory, CRF₁ antagonists and radio diagnostics. The structure-activity relationship (SAR) studies have acquired greater attention amid medicinal chemists, and many of the lead compounds were derived for various disease targets. However, there is plenty of room for the medicinal chemists to further exploit this privileged scaffold in developing potential drug candidates. The present review briefly outlines relevant synthetic strategies employed for pyrazolo[1,5-a]pyrimidine derivatives. It also extensively reveals significant biological properties along with SAR studies. To the best of our understanding current review is the first attempt made towards the compilation of significant advances made on pyrazolo[1,5-a]pyrimidines reported since 1980s.

Regioselective Synthesis of 7-(Trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines via Reaction of Pyrazolamines with Enynones

Condensation of enynones readily available from cheap starting material with pyrazolamines provides easy access to fluorescent 7-(trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines. The reaction is straightforward, does not require the use of any additional reagents or catalysts, and can be performed without inert atmosphere. Various substituents and functional groups in both enynone and pyrazolamine are tolerated. The presented method features full regioselectivity, high isolated yields, and simplicity of both setup and product purification. Fluorescent properties of the obtained pyrazolopyrimidines were studied.

Discovery of imidazopyridazines as potent Pim-1/2 kinase inhibitors

High levels of Pim expression have been implicated in several hematopoietic and solid tumor cancers, suggesting that inhibition of Pim signaling could provide patients with therapeutic benefit. Herein, we describe our progress towards this goal using a screening hit (rac-1) as a starting point. Modification of the indazole ring resulted in the discovery of a series of imidazopyridazine-based Pim inhibitors exemplified by compound 22m, which was found to be a subnanomolar inhibitor of the Pim-1 and Pim-2 isoforms (IC₅₀ values of 0.024nM and 0.095nM, respectively) and to potently inhibit the phosphorylation of BAD in a cell line that expresses high levels of all Pim isoforms, KMS-12-BM (IC₅₀=28nM). Profiling of Pim-1 and Pim-2 expression levels in a panel of multiple myeloma cell lines and correlation of these data with the potency of compound 22m in a proliferation assay suggests that Pim-2 inhibition would be advantageous for this indication.

I2-Catalyzed Multicomponent Reactions for Accessing Densely Functionalized Pyrazolo[1,5-a]pyrimidines and Their Disulphenylated Derivatives

New I2-catalyzed multicomponent bicyclization reactions of β-ketonitriles with sulfonyl hydrazides have been established, providing a direct and metal-free access toward unreported pyrazolo[1,5-a]pyrimidin-4-ium sulfonates. The latter could be quantitatively converted into densely functionalized pyrazolo[1,5-a]pyrimidines in the presence of bases. Using sulfonyl hydrazides as a sulfenylating agent, the resulting pyrazolo[1,5-a]pyrimidines enabled I2-catalyzed unprecedented disulphenylations to access fully substituted pyrazolo[1,5-a]pyrimidines through direct C(sp(2))-H bond bifunctionalization.

Design and synthesis of substituted pyrido[3,2-d]-1,2,3-triazines as potential Pim-1 inhibitors

A novel series of substituted pyrido[3,2-d]-1,2,3-triazines were designed and synthesized as Pim-1 inhibitors through scaffold hopping. Most of the derivatives showed potent in vitro Pim-1 inhibitory activities and anti-proliferative effects toward prostate cancer cells. Among them, 6b, 6h and 6m showed the best Pim-1 inhibitory activity with IC50 values of 0.69, 0.60 and 0.80 μM, respectively. Furthermore, compounds 6b, 6i, 6j and 6m showed strong inhibitory activity to human prostate cancer LNcap and PC-3 cell lines with IC50 values at low micromolar level. Structure-activity relationship analysis revealed that appropriate substitutions at C-6 positions contributed to the kinase inhibition and antiproliferative effects. Moreover, western blot assay suggested that 6j could decrease the levels of p-BAD and p-4E-BP1 in a dose-dependent manner in PC-3 cells. Docking studies showed that 3-N of the scaffold formed a hydrogen bond with Lys67, aromatic 4-aniline formed a key π-π stack with Phe49. Taken together, this study might provide the first sight for developing the pyrido[3,2-d]-1,2,3-triazine scaffold as novel Pim-1 inhibitors.

Carbon-Carbon Bond Cleavage Reaction: Synthesis of Multisubstituted Pyrazolo[1,5-a]pyrimidines

A new carbon-carbon bond cleavage reaction was developed for the efficient synthesis of multisubstituted pyrazolo[1,5-a]pyrimidines. This base induced reaction of 1,3,5-trisubstituted pentane-1,5-diones and substituted pyrazoles afforded good yields of the pyrazolo[1,5-a]pyrimidines.