Chemodivergent phosphonylation of diazocarboxylates: light-on vs. light-off reactions.

By tapping into the divergent reactivity of diazocarboxylates under thermal and photocatalytic conditions, we could develop chemodivergent phosphonylation protocols for α-diazocarboxylates with trialkyl phosphites. While the thermal reaction led to N-P bond formation affording phosphonylated hydrazones, the visible light-mediated reaction furnished phosphonylated aryl carboxylates through C-P bond formation. Both reactions are notable for their operational simplicity and mild conditions affording products in good yields without the requirement of a metal, base or photocatalyst.

Use of an anti-CD200-blocking antibody improves immune responses to AML in vitro and in vivo.

Treatment of relapsed/resistant acute myeloid leukaemia (AML) remains a significant area of unmet patient need, the outlook for most patients remaining extremely poor. A promising approach is to augment the anti-tumour immune response in these patients; most cancers do not activate immune effector cells because they express immunosuppressive ligands. We have previously shown that CD200 (an immunosuppressive ligand) is overexpressed in AML and confers an inferior overall survival compared to CD200low/neg patients. Here we show that a fully human anti-CD200 antibody (TTI-CD200) can block the interaction of CD200 with its receptor and restore AML immune responses in vitro and in vivo.

Redox-Neutral 1,3-Dipolar Cycloaddition of 2H-Azirines with 2,4,6-Triarylpyrylium Salts under Visible Light Irradiation.

A novel visible light mediated redox-neutral 1,3-dipolar cycloaddition of 2H-azirines with 2,4,6-triarylpyrylium tetrafluoroborate salts providing tetrasubstituted pyrroles has been developed. The 2,4,6-triarylpyrylium salt acts as dipolarophile as well as photosensitizer in the reaction, under blue light irradiation. The control experiments indicated single electron oxidation of 2H-azirines by photoexcited pyrylium salts, followed by coupling between an azaallenyl radical cation and triarylpyranyl radical as the key mechanistic feature. The mild conditions, wide substrate scope, and complete regioselectivity are the noticeable attributes of the reaction.

Regioselective synthesis of functionalized pyrazole-chalcones via a base mediated reaction of diazo compounds with pyrylium salts.

A base-mediated reaction of triaryl/alkyl pyrylium tetrafluoroborate salts with α-diazo-phosphonates, sulfones and trifluoromethyl compounds affords the corresponding functionalized pyrazole-chalcones as 5-P-5 and 3-P-3 tautomeric mixture. The reaction proceeds through an initial nucleophilic addition of diazo substrates to pyrylium salts followed by a base-mediated pyrylium ring-opening and intramolecular 1,5-cyclization to afford formal 1,3-dipolar cycloaddition products. The products underwent a Nazarov-type cyclization upon hydride reduction followed by acidic-workup, furnishing the corresponding indenyl-pyrazoles in high yields.

Visible light catalyzed synthesis of quinolines from (aza)-Morita-Baylis-Hillman adducts.

A mild and efficient protocol for the synthesis of quinoline scaffolds from (aza)-MBH adducts under visible light catalysis has been established. The reaction involves visible light catalyzed generation of amidyl radicals from (aza)-MBH adducts followed by intramolecular radical cyclization. The reaction exhibits a wide substrate scope, good functional group tolerance and high regioselectivity. This is the first example of utilizing (aza)-MBH adducts for the generation of amidyl radicals and synthesizing aza-heterocycles under visible light photoredox catalyzed reaction conditions.

Intramolecular trapping of ammonium ylides with N-benzoylbenzotriazoles in aqueous medium: direct access to the pseudoindoxyl scaffold.

The present work documents an operationally simple, clean and practical method for accessing the 2,2-disubstituted indolin-3-one (pseudoindoxyl) scaffold. The rhodium carbenoid mediated reaction between N-o-alkylamino benzoylbenzotriazoles and aryl diazoacetates occurs smoothly in water and exploits the leaving group ability of the benzotriazole moiety to install the carbonyl function in the product. Other highlights of the methodology are a wide substrate scope and experimental practicality given the re-use of the benzotriazole byproduct for starting material preparation.

Visible light catalyzed reaction of α-bromochalcones with chalcones: direct access to the urundeuvine scaffold.

The α-keto vinyl radicals generated from α-bromochalcones under visible light photoredox catalyzed conditions were trapped by chalcones. The subsequent intramolecular cyclization of the resulting benzylic radicals led to the synthesis of dihydronaphthalenes, which were conveniently oxidized to the corresponding naphthalenes. The strategy was adopted successfully for synthesizing derivatives of urundeuvine chalcones, which are otherwise accessible only from natural sources.

Visible light catalyzed Mannich reaction between tert-amines and silyl diazoenolates.

The present work documents the α-C-H functionalization of tertiary amines via the visible light catalyzed Mannich reaction with silyl diazoenolates. The reaction takes place at room temperature with an organic dye, Rose Bengal, as a photocatalyst and oxygen as the oxidant. The resulting multifunctional products bearing an α-diazo-ß-keto group undergo Rh-carbenoid mediated cyclization, affording stable ammonium ylides in high yields.

Unsaturated Phosphonates as Hauser Acceptors for the Synthesis of Phosphonylated Dihydroxynaphthalenes and Naphthoquinones.

The unsaturated phosphonates were utilized as Hauser acceptors successfully for the first time. The products phosphonylated 1,4-dihydroxynaphthalenes were isolated in good yields in short reaction time and were further oxidized to the corresponding 1,4-naphthoquinones in quantitative yields. The reaction provides an efficient and straightforward approach for the synthesis of pharmacologically privileged disubstituted naphthalene-1,4-diols and naphtha-1,4-diones bearing a phosphonate group at the 2-position and various (het)aryl groups at the 3-position.

Access to the Phosphorylindenopyrazole Scaffold via a Metal-Free Domino Reaction of Diazoalkylphosphonates with 3-Bromophthalides.

A novel strategy is reported here for the synthesis of an indenopyrazole scaffold bearing a phosphonate group. The entire sequence includes nucleophilic addition-elimination, Seyferth-Gilbert homologation, transphosphorylation, and a 1,3-dipolar cycloaddition reaction of diazoalkylphosphonates in a perfect "domino" manner.

Synthesis of α-diazo-ß-keto esters, phosphonates and sulfones via acylbenzotriazole-mediated acylation of a diazomethyl anion.

We report a method for the synthesis of α-diazo-ß-keto esters, phosphonates and sulfones via acylation of corresponding diazomethyl anions with N-acylbenzotriazoles. The N-o-amino-acylbenzotriazoles exhibited an unprecedented transphosphorylation reaction leading to diazoacetyl phenylphosphoramidates.

Anticancer and Antioxidant activity of Zingiber officinale Roscoe rhizome.

Dietary components present in foods, spices and herbs are source of natural compounds viz. phenols, flavonoids, tocopherols, ascorbic acid and carotenoids with potential benefits. Ginger is one such herb commonly used throughout the world as a spice for dietary as well as medicinal purpose since ancient period. Here, we investigated the methanolic extract of Zingiber officinale rhizome (ZOME) for anticancer activity against human cervical cancer HeLa cells and breast cancer MDA-MB-231 cells and antioxidant activity using 1,1-diphenyl-2-picryl hydroxyl (DPPH) scavenging assay, 2,2'-azinobis-3-ethylbenzothiozoline-6-sulfonic acid (ABTS) cation decolorization test. Antiproliferative activity was substantiated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and colony formation assay for cell viability and cell proliferation, Hoechst staining was performed to examine apoptosis. Our results demonstrated that ZOME inhibited the proliferation and colony formation in HeLa and MDA-MB-231 cells, in a dose- and time-dependent manner and induced typical changes in nuclear morphology, chromatin condensation and fragmentation, membrane shrinkage and blebbing in both cells indicated apoptotic property of Z. officinale. ZOME exhibited potent antiradical activity against DPPH and ABTS. On the basis of the results of the present study, it may be suggested that Z. officinale has promising anticancer and antioxidant properties. Since, Z officinale has been commonly used throughout the world as a spice for dietary as well as for medicinal purposes since prehistoric times. Therefore, enriched use of Z. officinale as dietary material could be recommended in ethno-medicine for the management of cervical and breast cancers. Moreover, further studies are needed to isolate and characterize the potent compounds for further adjuvant therapy against such malignancies.

Synthesis of α-diazo-ß-keto esters, phosphonates and sulfones via acylbenzotriazole-mediated acylation of a diazomethyl anion.

We report a method for the synthesis of α-diazo-ß-keto esters, phosphonates and sulfones via acylation of corresponding diazomethyl anions with N-acylbenzotriazoles. The N-o-amino-acylbenzotriazoles exhibited an unprecedented transphosphorylation reaction leading to diazoacetyl phenylphosphoramidates.

Attenuated neuroprotective effect of riboflavin under UV-B irradiation via miR-203/c-Jun signaling pathway in vivo and in vitro.

BACKGROUND: Riboflavin (RF) or vitamin B2 is known to have neuroprotective effects. In the present study, we report the attenuation of the neuroprotective effects of RF under UV-B irradiation. Preconditioning of UV-B irradiated riboflavin (UV-B-RF) showed attenuated neuroprotective effects compared to that of RF in SH-SY5Y neuroblostoma cell line and primary cortical neurons in vitro and a rat model of cerebral ischemia in vivo. RESULTS: Results indicated that RF pretreatment significantly inhibited cell death and reduced LDH secretion compared to that of the UV-B-RF pretreatment in primary cortical neuron cultures subjected to oxygen glucose deprivation in vitro and cortical brain tissue subjected to ischemic injury in vivo. Further mechanistic studies using cortical neuron cultures revealed that RF treatment induced increased miR-203 expression which in turn inhibited c-Jun expression and increased neuronal cell survival. Functional assays clearly demonstrated that the UV-B-RF preconditioning failed to sustain the increased expression of miR-203 and the decreased levels of c-Jun, mediating the neuroprotective effects of RF. UV-B irradiation attenuated the neuroprotective effects of RF through modulation of the miR-203/c-Jun signaling pathway. CONCLUSION: Thus, the ability of UV-B to serve as a modulator of this neuroprotective signaling pathway warrants further studies into its role as a regulator of other cytoprotective/neuroprotective signaling pathways.

Cell permeable vanX inhibitors as vancomycin re-sensitizing agents.

VanX is an induced zinc metallo d-Ala-d-Ala dipeptidase involved in the viable remodeling of bacterial cell wall that is essential for the development of VREF. Here we report two cyclic thiohydroxamic acid-based peptide analogs that were designed, synthesized and investigated as vancomycin re-sensitizing agents. These compounds exhibit low micromolar inhibitory activity against vanX, with low cytotoxicity and were shown to increase vancomycin sensitivity against VREF. The improved pharmacological properties of these novel inhibitors over previous transition state mimics should provide an enhanced platform for designing potent vanX inhibitors for overcoming vancomycin resistance.

Identification of novel inhibitors of human Chk1 using pharmacophore-based virtual screening and their evaluation as potential anti-cancer agents.

Kinases are one of the major players in cancer development and progression. Serine threonine kinases such as human checkpoint kinase-1 (Chk1), Mek1 and cyclin-dependent kinases have been identified as promising targets for cancer treatment. Chk1 is an important kinase with vital role in cell cycle arrest and many potent inhibitors targeted to Chk1 have been reported and few are currently in clinical trials. Considering the emerging importance of Chk1 inhibitors in cancer treatment there is a need to widen the chemical space of Chk1 inhibitors. In this study, we are reporting an integrated in silico approach to identify novel competitive Chk1 inhibitors. A 4-features pharmacophore model was derived from a co-crystallized structure of known potent Chk1 inhibitor and subjected to screen Maybridge compound library. Hits obtained from the screening were docked into the Chk1 active site and filtered on the basis of docking score and the number of pharmacophoric features showing conserved interaction within the active site of Chk1. Further, five compounds from the top ranking hits were subjected to in vitro evaluation as Chk1 inhibitor. After the kinase assay, four compounds were found to be active against human Chk1 (IC(50) range from 4.2 to 12.5 µM). Subsequent study using the cdc25-22 mutant yeast cells revealed that one of compound (SPB07479; IC(50) = 4.24 µM) promoted the formation of multinucleated cells, therefore overriding the cell cycle checkpoint. Validation studies using normal and human cancer cell lines, indicated that SPB07479 significantly inhibited proliferation of cervical cancer cells as a single agent and chemosensitized glioma and pancreatic cancer cell lines to standard chemotherapy while sparing normal cells. Additionally SPB07479 did not show significant cytotoxicity in normal cells. In conclusion we report that SPB07479 appear promising for further development of Chk1 inhibitors. This study also highlights the role of conserved water molecules in the active site of Chk1 for the successful identification of novel inhibitors.

Organophotoredox-mediated Formal [3+2]-Cycloaddition of 2H-Azirines with Aryldiazonium Salts: Direct Access to Trisubstituted 1,2,4-Triazoles.

The present work documents an organophotoredox-mediated formal [3+2]-cycloaddition of 2H-azirines with aryl diazonium tetrafluoroborate salts to furnish 1,3,5-trisubstituted 1,2,4-triazoles. The reaction furnishes a regioisomeric mixture of 1,2,4-triazoles in case of unsymmetrically substituted azirines. It is noteworthy that aryl radical generation from diazonium salt under visible light photoredox conditions could be successfully avoided by carefully selecting the reaction conditions.

Nuclear factor I-C overexpression promotes monocytic development and cell survival in acute myeloid leukemia.

Nuclear factor I-C (NFIC) belongs to a family of NFI transcription factors that binds to DNA through CAATT-boxes and are involved in cellular differentiation and stem cell maintenance. Here we show NFIC protein is significantly overexpressed in 69% of acute myeloid leukemia patients. Examination of the functional consequences of NFIC overexpression in HSPCs showed that this protein promoted monocytic differentiation. Single-cell RNA sequencing analysis further demonstrated that NFIC overexpressing monocytes had increased expression of growth and survival genes. In contrast, depletion of NFIC through shRNA decreased cell growth, increased cell cycle arrest and apoptosis in AML cell lines and AML patient blasts. Further, in AML cell lines (THP-1), bulk RNA sequencing of NFIC knockdown led to downregulation of genes involved in cell survival and oncogenic signaling pathways including mixed lineage leukemia-1 (MLL-1). Lastly, we show that NFIC knockdown in an ex vivo mouse MLL::AF9 pre-leukemic stem cell model, decreased their growth and colony formation and increased expression of myeloid differentiation markers Gr1 and Mac1. Collectively, our results suggest that NFIC is an important transcription factor in myeloid differentiation as well as AML cell survival and is a potential therapeutic target in AML.

Exploiting the umpolung reactivity of diazo groups: direct access to triazolyl-azaarenes from azaarenes.

The present work documents electrophilic substitution of azaarenes, mainly isoquinolines, with hypervalent iodine diazo reagents (HIDR) followed by formal [3+2]-dipolar cycloaddition in a tandem fashion. Other azaarenes viz. pyridines and phenanthridines too could be successfully used in the reaction. The methodology capitalizes on the umpolung nature of α-aryliodonio diazo compounds for installing a nucleophile, i.e. azaarene, at their α-position. Subsequent ylide formation and intramolecular 1,5-cyclization furnished 4,3-fused 1,2,4-triazolyl-azaarenes in good yields. The reaction is notable for its mild conditions, operational simplicity and fairly general scope.

Single cell analyses identify a highly regenerative and homogenous human CD34+ hematopoietic stem cell population.

The heterogeneous nature of human CD34+ hematopoietic stem cells (HSCs) has hampered our understanding of the cellular and molecular trajectories that HSCs navigate during lineage commitment. Using various platforms including single cell RNA-sequencing and extensive xenotransplantation, we have uncovered an uncharacterized human CD34+ HSC population. These CD34+EPCR+(CD38/CD45RA)- (simply as EPCR+) HSCs have a high repopulating and self-renewal abilities, reaching a stem cell frequency of ~1 in 3 cells, the highest described to date. Their unique transcriptomic wiring in which many gene modules associated with differentiated cell lineages confers their multilineage lineage output both in vivo and in vitro. At the single cell level, EPCR+ HSCs are the most transcriptomically and functionally homogenous human HSC population defined to date and can also be easily identified in post-natal tissues. Therefore, this EPCR+ population not only offers a high human HSC resolution but also a well-structured human hematopoietic hierarchical organization at the most primitive level.