- An Unsymmetrical Squaraine-Based Activatable Probe for Imaging Lymphatic Metastasis by Responding to Tumor Hypoxia with MSOT and Aggregation-Enhanced Fluorescent Imaging
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Optoacoustic imaging has great potential for preclinical research and clinical practice, and designing robust activatable optoacoustic probes for specific diseases is beneficial for its further development. Herein, an activatable probe has been developed for tumor hypoxia imaging. For this probe, indole and quinoline were linked on each side of an oxocyclobutenolate core to form an unsymmetrical squaraine. A triarylamine group was incorporated to endow the molecule with the aggregation enhanced emission (AEE) properties. In aqueous media, the squaraine chromophore aggregates into the nanoprobe, which specifically responds to nitroreductase and produces strong optoacoustic signals due to its high extinction coefficient, as well as prominent fluorescence emission as a result of its AEE feature. The nanoprobe was used to image tumor metastasis via the lymphatic system both optoacoustically and fluorescently. Moreover, both the fluorescence signals and three-dimensional multispectral optoacoustic tomography signals from the activated nanoprobe allow us to locate the tumor site and to map the metastatic route.
- Lin, Yi,Sun, Lihe,Zeng, Fang,Wu, Shuizhu
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Read Online
- Efficient far red sensitization of nanocrystalline TiO2 films by an unsymmetrical squaraine dye
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An asymmetric squaraine sensitizer comprising an anchoring group was engineered at the molecular level and synthesized. The functionalized novel squaraine sensitizers upon anchoring onto a TiO2 film exhibit an unprecedented incident photon to current conversion efficiency of 85%. The photovoltaic data of this sensitizer using an electrolyte having composition of 0.6 M M-methyl-N-butyl imidazolium iodide, 0.05 M iodine, 0.1 M LiI, 0.05 M tert-butylpyridine in a 15/85 (v/v) mixture of valeronitrile and acetonitrile revealed a short circuit photocurrent density of 10.5 ± 0.2 mA/cm2, an open circuit voltage of 603 ± 10 mV, and a fill factor of 0.71 ± 0.02, corresponding to an overall conversion efficiency of 4.50% under standard AM 1.5 sunlight. Copyright
- Yum, Jun-Ho,Walter, Pablo,Huber, Simon,Rentsch, Daniel,Geiger, Thomas,Nueesch, Frank,De Angelis, Filippo,Graetzel, Michael,Nazeeruddin, Mohammad K.
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Read Online
- Multiple linker half-squarylium dyes for dye-sensitized solar cells; Are two linkers better than one?
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The synthesis and full characterization of new half-squaraine dyes (Hf-SQ) containing two or three carboxylate-based linker units is reported and these dyes tested in dye-sensitized solar cell (DSC) devices. The data show improved device efficiency for a Hf-SQ dye with two linkers (η = 5.5%) compared to the highest efficiency Hf-SQ previously reported which had only a single linker (η = 5.0%); this is mainly due to improved Voc. To understand the effects of using multiple dye linker groups, device I-V data have been correlated with single crystal X-ray structural analysis and dye electrical properties (both in solution and adsorbed to TiO2) using UV-visible and ATR-IR spectroscopy along with cyclic voltammetry, and also theoretical studies using density functional theory (DFT) calculations. These data show that positioning the linkers near the dye LUMO and so that this enables complete linker chemisorption are key factors for device performance.
- Connell, Arthur,Holliman, Peter J.,Jones, Eurig W.,Furnell, Leo,Kershaw, Christopher,Davies, Matthew L.,Gwenin, Christopher D.,Pitak, Mateusz B.,Coles, Simon J.,Cooke, Graeme
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Read Online
- Cyclic sulfone compound and preparation method, application and pharmaceutical composition thereof
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The invention belongs to the technical field of pharmacy, and relates to a cyclic sulfone compound and a preparation method, application and a pharmaceutical composition thereof. The cyclic sulfone compound is shown as a formula (I), is a CXCR2 antagonist
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Paragraph 0286; 0288; 0289; 0290
(2021/05/29)
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- The Impact of Chiral Citronellyl-Functionalization on Indolenine and Anilino Squaraine Thin Films
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The impact on chiral aggregation in solution processed and thermally annealed thin films of two indolenine and one anilino squaraines with chiral (S)-citronellyl functionalization at the nitrogen of the squaraine backbone is investigated. A pseudo polymor
- Balzer, Frank,Beverina, Luca,Lützen, Arne,Mattiello, Sara,Meerholz, Klaus,Schiek, Manuela,Schmidtmann, Marc,Schulz, Matthias,Schumacher, Marvin F.,Serdar Sariciftci, N.,Zablocki, Jennifer
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- Carboxyl-modified near-infrared squaric acid dye as well as preparation method and application thereof
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The invention discloses a carboxyl-modified near-infrared squaric acid dye as well as a preparation method and application thereof. The carboxyl-modified near-infrared squaric acid dye is prepared by taking a carboxyl-modified 2-methylbenzothiazole derivative and a dicyanovinyl squaric acid derivative as raw materials. The near-infrared squaric acid dye has relatively good stability and excellent optical performance, and particularly, the water solubility of the dye can be enhanced by carboxylic acid groups. When the near-infrared squaric acid dye is used for detecting parallel and mixed G-quadruplex, the G-quadruplex can interact with dye molecules, and a dye absorption spectrum and a fluorescence emission spectrum are changed while the topological structure of the G-quadruplex is not changed, so that the near-infrared squaric acid dye can be used as a fluorescent probe for detecting the parallel and mixed G-quadruplex.
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Paragraph 0016
(2021/08/28)
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- Near-infrared double-acid dye connected with oxygen ether chain as well as preparation method and application thereof
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The invention discloses a near-infrared double-acid dye connected with an oxygen ether chain, and preparation and application thereof. The 2 -methylbenzothiazole derivative and dicyanovinyl modified semiaromatic acid derivative which is linked with an oxygen ether chain is prepared from a raw material. The near-infrared both-side acid dye has good stability and excellent optical performance, and especially the introduction of a sulfonic acid group and an oxygen ether chain can enhance the water solubility of the dye. When the near-infrared double-acid dye is used for detection G - quadruplex, G - quadruplex can interact with the dye molecules, and the change of the dye absorption spectrum and the fluorescence spectrum is caused while G - quadruplex topological structure changes, so that the dye can be used as G - quadruplex. Fluorescent probes for detection.
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Paragraph 0023
(2021/09/08)
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- Novel bisubstrate uridine-peptide analogues bearing a pyrophosphate bioisostere as inhibitors of human O-GlcNAc transferase
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Protein O-linked β-D-N-acetylglucosamine (O-GlcNAc) modification (O-GlcNAcylation), an essential post-translational as well as cotranslational modification, is the attachment of β-D-N-acetylglucosamine to serine and threonine residues of nucleocytoplasmic proteins. An aberrant O-GlcNAc profile on certain proteins has been implicated in metabolic diseases such as diabetes and cancer. Inhibitors of O-GlcNAc transferase (OGT) are valuable tools to study the cell biology of protein O-GlcNAc modification. In this study we report novel uridine-peptide conjugate molecules composed of an acceptor peptide covalently linked to a catalytically inactive donor substrate analogue that bears a pyrophosphate bioisostere and explore their inhibitory activities against OGT by a radioactive hOGT assay. Further, we investigate the structural basis of their activities via molecular modelling, explaining their lack of potency towards OGT inhibition.
- Ryan, Philip,Shi, Yun,von Itzstein, Mark,Rudrawar, Santosh
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- Design and Synthesis of Near-Infrared Mechanically Interlocked Molecules for Specific Targeting of Mitochondria
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The entrapment of squaraine (SQ) within a molecular container to form rotaxane has been shown to improve the dye stability and the fluorescence proficiency inside the mitochondria. The macrocycle provides shelter and protects the near-infrared (NIR) SQ chromophore from nucleophilic attacks made by the exposed thiol of Cys-containing mitochondrial proteins and mitochondrial glutathione. Herein a microwave-assisted template-directed clipping reaction on low-loading 2-chlorotrityl chloride resin is used to develop an NIR unsymmetrical squaraine rotaxane in high quantum yield.
- Chatterjee, Sudipta,Das, Rabi Sankar,Guha, Samit,Mukherjee, Ayan,Saha, Pranab Chandra,Sepay, Nayim
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supporting information
(2020/08/05)
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- An Expedient Synthesis of Tacrine-Squaric Hybrids as Potent, Selective and Dual-Binding Cholinesterase Inhibitors
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The restoration of acetylcholine levels in the brain by inhibition of cholinesterases is currently the most successful therapeutic strategy to treat neurodegenerative disorders. In this context, tacrine has been largely investigated as a starting scaffold for the development of promising new anticholinesterases compounds for the treatment of neurodegenerative illnesses, including Alzheimer’s disease. Here we present a series of compounds containing the tacrine nucleus connected with squaric moiety by a diaminoalkylene chain. The compounds were obtained through a simple and short synthetic route and showed high inhibitory activity against acetylcholinesterase (AChE) within nanomolar IC50 (half maximal inhibitory concentration). The molecular modelling study showed that these compounds act as dual-binding inhibitors of AChE, interacting with both catalytic active site (CAS) and peripheral anionic site (PAS) of the enzyme’s binding cavity. The investigated compounds also demonstrated outstanding selectivity for AChE than in butyrylcholinesterase (BuChE). These results evince these compounds as promising agents for the treatment of neurodegenerative disorders and a fuller synthetic scope jointly with complementary biological evaluations are currently under investigation in our laboratory.
- Afolabi, Blessing A.,Ceschi, Marco A.,Dapont, Henrique,Dardenne, Laurent E.,Guedes, Isabella A.,Lopes, Jo?o P. B.,Pilotti, Renan M.,da Rocha, Jo?o B. T.
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p. 857 - 866
(2020/10/07)
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- Pyridinium ion modified near infrared squaric acid dye as well as preparation and application thereof
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The invention discloses pyridinium ion modified near infrared squaric acid dye as well as a preparation method and application thereof. Pyridinium ion modified trimethyl dihydroindole derivatives anddicyanovinyl square acid derivatives are used as raw materials to prepare the near infrared squaric acid dye. The near infrared squaric acid dye has high stability and excellent optical performance; particularly pyridinium ion groups can enhance the dye water solubility; when the near infrared squaric acid dye is used for aquacide detection, aquacide molecules and dye molecules can mutually act, so that the absorption spectrum and fluorescence spectrum change can be caused, so that the materials can be used as fluorescence probes for aquacide detection, can be used for aquacide fluorescence detection in the environment, and has higher detection sensitivity.
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Paragraph 0023
(2019/06/07)
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- Near-infrared squaraine fluorescent probe for imaging adenosine 5′-triphosphate in live cells
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Adenosine 5′-triphosphate (ATP), as a “molecular currency” for intracellular energy transfer, not only participates in various physiological activities, but also involves in various pathological processes of living cells. Therefore, the establishment of a simple, rapid, sensitive and accurate ATP analysis method is of great significance for the study of its physiological functions. In this work, we rationally design a near-infrared phenylboronic acid group-functionalized dicyanovinyl squaraine (SQ-PBA3), with which a supramolecular assembly was constructed for fluorescent imaging of ATP. In PBS buffer, SQ-PBA3 changes self-assembly when adding cetyltrimethyl ammonium bromide (CTAB) deriving fluorescence response of SQ-PBA3 to ATP with the maximum emission at 700 nm, due to the specificity of phenylboronic acid to diols and the multiple electrostatic interactions between SQ-PBA3, ATP and CTAB molecules. Meanwhile, the probe was successfully applied to monitor intracellular ATP level in MCF-7 cells with high sensitivity and selectivity.
- Wang, Guimei,Jiang, Xiaoxue,Fu, Nanyan
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- Mn(III)-based oxidative radical ring-expansion reaction using squarate derivatives: Selective synthesis of bis(butenolide)s and the acetate monomers
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The Mn(III)-based oxidation of phenyl- and alkyl-substituted hydroxycyclobutenones selectively produced the bis(butenolide)s or the acetate monomers via the 5-endo radical cyclization depending upon the concentration of the reaction. A similar reaction of hydroxycyclobutenones bearing an alkenyl and alkynyl substituent did not produce any bis(butenolide)s or acetate monomers, but the 5-exo and 6-endo radical cyclization products including the unsaturated group. The oxidation of the hydroxycyclobutenones having an unsaturated substituent in the presence of alkenes afforded radical coupling products during the 5-exo radical cyclization. The reaction details, structure determination of the products, and the mechanism for the formation of the products are described.
- Sasaki, Jun-Ichi,Kobayashi, Makoto,Ibe, Y?suke,Nishino, Hiroshi
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p. 958 - 988
(2019/08/01)
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- Phenylboronic acid modified near-infrared squaraine dyes as well as preparation method and application thereof
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The invention discloses phenylboronic acid modified near-infrared squaraine dyes as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing an indole-modified phenylboronic acid derivative with a dicyanyl vinyl squaraine derivative; carrying out dissolution, backflow, pressure-reduction evaporation-removal on a solvent and silica gel column chromatography purification to obtain the near-infrared squaraine dyes. The squaraine dyes have the advantages of better stability and excellent optical performance, in particular to contraposition-substituted phenylboronic acid groups; the squaraine dyes can be partially combined with cis-glycol in an ATP (adenosinetriphosphate) molecule, so that change of absorption spectrum and fluorescence spectrum of the dyes is induced through multiple electrostatic interactions among the dyes, the ATP and CTAB (Cetyl Trimethyl Ammonium Bromide), so that the dyes can be used as fluorescent probes for ATP detection, and the fluorescent probes are used for carrying out fluorescent imaging detection on the ATP in cells; moreover, the probes have the advantages of better biocompatibility and cellular permeability and lower biotoxicity, and has better detection sensitivity on ATP.
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Paragraph 0026
(2018/11/03)
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- Small-Molecule Inhibition of the UNC119–Cargo Interaction
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N-Terminal myristoylation facilitates membrane binding and activity of proteins, in particular of Src family kinases, but the underlying mechanisms are only beginning to be understood. The chaperones UNC119A/B regulate the cellular distribution and signal
- Mejuch, Tom,Garivet, Guillaume,Hofer, Walter,Kaiser, Nadine,Fansa, Eyad K.,Ehrt, Christiane,Koch, Oliver,Baumann, Matthias,Ziegler, Slava,Wittinghofer, Alfred,Waldmann, Herbert
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supporting information
p. 6181 - 6186
(2017/05/22)
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- A series of asymmetric squaraine cyanine small molecule and its preparation method and application
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The invention discloses a series of asymmetrical squarine micromolecules as well as a preparation method and an application thereof. Donor-receptor-donor type asymmetrical squarine micromolecules are formed by adopting two different electron-rich aromatic units as donors and leading 1,3-squaric acid cells with high electronic affinity into a conjugated system as receptors, so that micromolecule materials with low band gaps are acquired, and the absorption spectrum of the micromolecule materials can cover visual and near-infrared regions by 450-800nm; and meanwhile, the compounds prepared through the preparation method are good in dissolubility and film-forming property, which is very favorable for preparing organic solar cells with good performance.
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Paragraph 0051
(2016/10/07)
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- Triggering apoptosis in cancer cells with an analogue of cribrostatin 6 that elevates intracellular ROS
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Elevation of reactive oxygen species (ROS) is both a consequence and driver of the upregulated metabolism and proliferation of transformed cells. The resulting increase in oxidative stress is postulated to saturate the cellular antioxidant machinery, leaving cancer cells susceptible to agents that further elevate their intracellular oxidative stress. Several small molecules, including the marine natural product cribrostatin 6, have been demonstrated to trigger apoptosis in cancer cells by increasing intracellular ROS. Here, we report the modular synthesis of a series of cribrostatin 6 derivatives, and assessment of their activity in a number of cell lines. We establish that placing a phenyl ring on carbon 8 of cribrostatin 6 leads to increased potency, and observe a window of selectivity towards cancer cells. The mechanism of activity of this more potent analogue is assessed and demonstrated to induce apoptosis in cancer cells by increasing ROS. Our results demonstrate the potential for targeting tumors with molecules that enhance intracellular oxidative stress.
- Asby,Radigois,Wilson,Cuda,Chai,Chen,Bienemann,Light,Harrowven,Tavassoli
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supporting information
p. 9322 - 9330
(2016/10/13)
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- Synthesis and biological evaluation of N, N ′-squaramides with high in vivo efficacy and low toxicity: Toward a low-cost drug against Chagas disease
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Access to basic drugs is a major issue in developing countries. Chagas disease caused by Trypanosoma cruzi is a paradigmatic example of a chronic disease without an effective treatment. Current treatments based on benznidazole and nifurtimox are expensive, ineffective, and toxic. N,N′-Squaramides are amide-type compounds that feature both hydrogen bond donor and acceptor groups and are capable of multiple interactions with complementary sites. When combined with amine and carboxylic groups, squaramide compounds have increased solubility and therefore make suitable therapeutic agents. In this work, we introduce a group of Lipinski's rule of five compliant squaramides as candidates for treating Chagas disease. The in vivo studies confirmed the positive expectations arising from the preliminary in vitro studies, revealing compound 17 to be the most effective for both acute and chronic phases. The activity, stability, low cost of starting materials, and straightforward synthesis make amino squaramides appropriate molecules for the development of an affordable anti-Chagasic agent.
- Olmo, Francisco,Rotger, Carmen,Ramírez-Macías, Inmaculada,Martínez, Luis,Marín, Clotilde,Carreras, Lucas,Urbanová, Kristína,Vega, Manel,Chaves-Lemaur, Guillermo,Sampedro, Angel,Rosales, María Jose,Sánchez-Moreno, Manuel,Costa, Antonio
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p. 987 - 999
(2014/03/21)
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- Design and synthesis of novel C2-symmetric chiral shift reagents derived from squaramide and their recognition of anions and chiral carboxylate anions
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The novel, recyclable C2-symmetric chiral shift reagents bearing both squaramide and indanol groups have been synthesized. These squaramides were examined as chiral shift reagents, and they have a wide recognition towards chiral carboxylate anions. The squaramide derived from (1S, 2R)-1-amino-2-indanol can distinguish the absolute configuration of the guest carboxylate anion.
- Zhou, Enshan,Zhang, Jin,Lu, Yuzhi,Dong, Chune
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p. 351 - 364
(2015/01/08)
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- Novel high performance asymmetrical squaraines for small molecule organic solar cells with a high open circuit voltage of 1.12 v
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An asymmetrically substituted squaraine ASQC bearing a 9-carbazyl substituent exhibits an extremely deep HOMO energy level of -5.46 eV and a relatively low bandgap of 1.65 eV, hence renders solution-processed organic solar cells with an impressive Vo
- Yang, Daobin,Yang, Qianqian,Yang, Lin,Luo, Qian,Huang, Yan,Lu, Zhiyun,Zhao, Suling
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supporting information
p. 10465 - 10467
(2013/11/06)
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- Design, synthesis and biological evaluation of novel estrogen-derived steroid metal complexes
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A new series of estrogen-derived metal complexes were synthesized and characterized. The functionalized estrogen receptor ligands were prepared by a four-step synthetic strategy, and then three transition metal Pd, Ni, Zn were introduced readily to give t
- Zhang, Xinlong,Zuo, Ziqing,Tang, Juan,Wang, Kai,Wang, Caihua,Chen, Weiyan,Li, Changhao,Xu, Wen,Xiong, Xiaolin,Yuntai, Kangxiang,Huang, Jian,Lan, Xiaoli,Zhou, Hai-Bing
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supporting information
p. 3793 - 3797
(2013/07/27)
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- The regioselectivity and synthetic mechanism of 1,2-benzimidazole squaraines: Combined experimental and theoretical studies
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In this paper, a synthetic method to produce 1,2-benzimidazole squaraines with a yield of up to 89% is developed. It is found that both strong organic and inorganic bases have a satisfactory catalytic activity for this reaction. Theoretical studies provide detailed explanations for the 1,2 versus 1,3 condensation regiochemistry of the squaraines. The experimental and theoretical studies agree well with each other, paving a practical way to efficiently synthesize 1,2-squaraines. The Royal Society of Chemistry.
- Xia, Guomin,Wu, Zhiwei,Yuan, Yanli,Wang, Hongming
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p. 18055 - 18061
(2013/10/01)
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- Design and synthesis of heterocyclic enamine derivatives based on skeleton of neonicotinoids
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Novel heterocyclic enamine derivatives based on skeleton of neonicotinoids were designed and prepar ed by the substitution reaction between heterocyclic enamines with intermediates of neonicotinoids, which provides readily accessible neonicotinoid analogs
- Liu, Chuanxiang,Yi, Fengping,Zou, Jianzhong
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p. 113 - 116
(2013/01/16)
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- Squaramides as potent transmembrane anion transporters
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Square peg in a round ball: Squaramides are shown to be potent transmembrane anion transporters for both chloride and bicarbonate, performing better than the thiourea and urea analogues. Studies into the nature of this transport point to a mobile carrier mechanism, where the squaramide delivers the anion cargo across the lipid bilayer (see scheme, green sphere=anion). These drug-like molecules provide a platform for the development of a new generation of anion-transport systems. Copyright
- Busschaert, Nathalie,Kirby, Isabelle L.,Young, Sarah,Coles, Simon J.,Horton, Peter N.,Light, Mark E.,Gale, Philip A.
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supporting information; experimental part
p. 4426 - 4430
(2012/06/04)
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- Structural effects on interconversion of oxygen-substituted bisketenes and cyclobutenediones
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(Graph Presented) Cyclobutenediones 5 disubstituted with HO (a), MeO (b), EtO (c), i-PrO (d), t-BuO (e), PhO (f), 4-MeOC6H4O (g), 4-O2NC6H4O (h), and 3,4-bridging OCH 2CH2O (i) substituents upon laser flash photolysis gave the corresponding bisketenes 6a-i, as detected by their distinctive doublet IR absorptions between 2075 and 2106 and 2116 and 2140 cm-1. The reactivities in ring closure back to the cyclobutenediones were greatest for the group 6b-e, with the highest rate constant of 2.95 ×107 s -1 at 25°C for 6e (RO = t-BuO) in isooctane, were less for 6a (RO = OH, k = 2.57 × 106 s-1 in CH3CN), while 6f- i were the least reactive, with the lowest rate constant of 3.8 × 104 s-1 in CH3CN for 6h (RO = 4-O 2NC6H4O). The significantly reduced rate constants for 6f-i are attributed to diminution of the electron-donating ability of oxygen to the cyclobutenediones 5f-h by the ArO substituents compared to alkoxy groups and to angle strain in the bridged product cyclobutenedione 5i. The reactivities of the ArO-substituted bisketenes 6f-h in CH3CN varied by a factor of 50 and gave an excellent correlation of the observed rate constants log k with the σp constants of the aryl substituents. Computational studies at the B3LYP/6-31G(d) level of ring-closure barriers are consistent with the measured reactivities. Photolysis of squaric acid (5a) in solution provides a convenient preparation of deltic acid (7).
- Fu, Nanyan,Allen, Annette D.,Kobayashi, Shinjiro,Tidwell, Thomas T.,Vukovic, Sinisa,Matsuoka, Takeshi,Mishima, Masaaki
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p. 1768 - 1773
(2008/09/18)
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- Synthesis of the substituted 3-cyclobutene-1,2-diones
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A convenient synthesis of the novel squaric acid derivatives is reported. Unsymmetrically substituted 3,4-diamino-3-cyclobutene-1,2-diones and 3-amino-4-hydroxy-3-cyclobutene-1,2-diones were prepared by interaction of diethyl squarate with different nucle
- Ivanovsky, Sergey A.,Dorogov, Mikhail V.,Kravchenko, Dmitry V.,Ivachtchenko, Alexandre V.
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p. 2527 - 2542
(2008/02/10)
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- Copper-mediated synthesis of tertiary diaryl squaramides
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(Chemical Equation Presented) Tertiary aryl squaramides were synthesized by using copper catalyzed C-N bond-formation with L-proline as the ligand. Symmetrical diaryl squaramides could be prepared in a one-pot reaction by using excess aryl bromide with va
- Ramalingam, Vijayakumar,Bhagirath, Niala,Muthyala, Rajeev S.
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p. 3976 - 3979
(2008/02/01)
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- Use of acylsulfonamido-substituted polymethine dyes as fluorescene dyes and/or markers
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The invention relates to a novel polymethine dyes containing at least one acylsulfonamido group of the formula (I) in which n, Y, A and R have the meaning given in the claims, and at least one compound of the formulae (a) to (n) given in the claims. The polymethine dyes according to the invention are suitable for use as dyes and/or labels, in particular for staining or labeling biomolecules.
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Page/Page column 61
(2008/06/13)
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- Design, synthesis and structure of new chiral squaric acid monoaminoalcohols and diaminoalcohols and their use as catalysts in asymmetric reduction of ketones and diketones
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Many chiral squaric acid aminoalcohols and C2-symmetric diaminoalcohols have been synthesized and their in situ formed chiral boron heterocycles have been used as catalysts for the enantioselective reduction of prochiral ketones and diketones by borane to give alcohols with up to 99% enantiomeric excess and 99% yield. The effects of solvent, catalyst-substrate ratio and temperature were also investigated.
- Zhou, Hai-Bing,Zhang, Ji,Lü, Shou-Mao,Xie, Ru-Gang,Zhou, Zhong-Yuan,Choi, Michael C.K,Chan, Albert S.C,Yang, Teng-Kuei
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p. 9325 - 9333
(2007/10/03)
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- An efficient general synthesis of squarate esters
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An efficient and general method for the synthesis of alkyl squarates is presented. This involves the reactions of squaric acid with the desired alcohol in the presence of an orthoformate. This was applicable for the synthesis of dimethyl-, diethyl-, diisopropyl, di-n-butyl and di-t-butyl squarates in yields ranging from 77-97%. It is a convenient and safe method that can be accomplished on a multigram scale.
- Liu, Hiu,Tomooka, Craig S.,Moore, Harold W.
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p. 2177 - 2180
(2007/10/03)
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- Synthesis of Squaric Acid Derivatives by Lewis Acid-catalysed Reaction of its Dichloride, Methyl Ester Chloride, Diethylamide Chloride, and Ethyl Diester with Unsaturated Organosilanes: New Method for C-C Bond Formation on Cyclobutenedione
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The squaric acid family of derivatives, e.g. dichloride 2, methyl ester chloride 3, diethyl amide chloride 4, and ethyl diester 5, reacted with a variety of unsaturated organosilanes 6 in the presence of a catalyst, typically titanium tetrachloride, at -7
- Ohno, Masatomi,Yamamoto, Yoshihiko,Shirasaki, Yuhichi,Eguchi, Shoji
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p. 263 - 272
(2007/10/02)
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- Preparation of 3-Alkoxy-4-alkyl-3-cyclobutene-1,2-diones
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Several squaric acid esters (2a-g) are prepared.They react with Grignard compounds to give the title compounds (11a-n). 1,2- vs. 1,4-Grignard addition and the benzyl-tolyl rearrangement coincidental with the Grignard reaction are discussed.Hydrolysis of compounds 11 leads to 4-alkyl-3-hydroxy-3-cyclobutene-1,2-diones (12).
- Dehmlow, Eckehard V.,Schell, Hans G.
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