Search results for "Squaric acid"
showing 10 items of 17 documents
AAZTA5-squaramide ester competing with DOTA-, DTPA- and CHX-A″-DTPA-analogues: Promising tool for 177Lu-labeling of monoclonal antibodies under mild …
2021
Abstract Background Combining the advantages of both cyclic and acyclic chelator systems, AAZTA (1,4-bis(carboxymethyl)-6-[bis(carboxymethyl)]amino-6-methylperhydro-1,4-diazepine) is well suited for complexation of various diagnostic and therapeutic radiometals such as gallium-68, scandium-44 and lutetium-177 under mild conditions. Due to its specificity for primary amines and pH dependent binding properties, squaric acid (SA) represents an excellent tool for selective coupling of the appropriate chelator to different target vectors. Therefore, the aim of this study was to evaluate radiolabeling properties of the novel bifunctional AAZTA5-SA being coupled to a model antibody (bevacizumab) i…
Targeting fibroblast activation protein (FAP): next generation PET radiotracers using squaramide coupled bifunctional DOTA and DATA5m chelators
2020
Abstract Background Fibroblast activation protein (FAP) is a proline selective serine protease that is overexpressed in tumor stroma and in lesions of many other diseases that are characterized by tissue remodeling. In 2014, a most potent FAP-inhibitor (referred to as UAMC1110) with low nanomolar FAP-affinity and high selectivity toward related enzymes such as prolyl oligopeptidase (PREP) and the dipeptidyl-peptidases (DPPs): DPP4, DPP8/9 and DPP2 were developed. This inhibitor has been adopted recently by other groups to create radiopharmaceuticals by coupling bifunctional chelator-linker systems. Here, we report squaric acid containing bifunctional DATA5m and DOTA chelators relied on UAMC…
Syntheses, crystal structures and magnetic properties of new oxalato-, croconato- and squarato-containing copper(ii) complexesElectronic supplementar…
2003
The preparation and magnetic investigation of five mononuclear copper(II) complexes of formula [Cu(pyim)(C2O4)(H2O)]·2H2O (1), [Cu(pyim)(C4O4)(H2O)2]·2H2O (2), Cu(pyim)(C5O5)·2.5H2O (3), [Cu(H2bim)(C2O4)(H2O)]·H2O (4) and [Cu(bpz)(C5O5)(H2O)] (5) [pyim=2-(2-pyridyl)imidazole, H2bim=2,2′-biimidazole, bpz=2,2′-bipyrazine, C2O42−=dianion of oxalic acid, C4O42−=dianion of squaric acid and C5O52−=dianion of croconic acid] are reported. The crystal structures of 1, 2, 4 and 5 have been determined. The copper atom has a distorted square pyramidal geometry in this family of complexes: two nitrogen atoms from the bidentate nitrogen donor [pyim (1 and 2), H2bim (4) and bpz (5)] and two oxygen atoms e…
Synthesis crystal structure and magnetic properties of [Fe2(bpym)(C5O5)2(H2O)4]·2H2O and two polymorphs of [Fe2(bpym)(C4O4)2(H2O)6]·2H2O (bpym = 2,2′…
1998
Abstract Two dinuclear iron(II) complexes of formulae [Fe2(bpym)(C5O5)2(H2O)4]·2H2O (1) and [Fe2(bpym)(C4O4)2(H2O)6]·2H2O (2) (bpym = 2,2-bipyrimidine, C5O52 = dianion of croconic acid (4,5-dihydroxycylopent-4-ene-1,2,3-trione) and C4O42 = dianion of squaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione)) were prepared and their crystal structures (at 103 K) determined by X-ray diffraction methods. The structure of 1 consists of neutral centrosymmetric [Fe2(bpym)(C5O5)2(H2O)4] units and water molecules of crystallization which are linked by an extensive network of hydrogen bonds. The coordination geometry around each iron atom is that of a compressed octahedron with bpym nitrogen atoms and cr…
Crystal structures and magnetic properties of the squarate-O1,On-bridged dinuclear copper(II) complexes [Cu2(phen)4(C4O4)](CF3SO3)2 · 3H2O (n=2) and …
1999
Abstract Two dinuclear copper(II) complexes of the formula [Cu2(phen)4(C4O4)](CF3SO3)2 · 3H2O (1) and [Cu2(bipy)4(C4O4)](CF3SO3)2 · 6H2O (2) [phen=1,10-phenanthroline, bipy=2,2′-bipyridine and C4O4 2−=dianion of 3,4-dihydroxy-3-cyclobuten-1,2-dione (squaric acid)] have been synthesized and characterized by single-crystal X-ray diffraction. Their structures consist of [Cu2(phen)4(C4O4)]2+ (1) and [Cu2(bipy)4(C4O4)]2+ (2) dinuclear copper(II) cations, uncoordinated CF3SO3 − anions and crystallization water molecules. The copper is in a distorted square pyramidal environment: one squarate-oxygen atom and three phen- (1) or bipy- (2) nitrogen atoms of two phen (1) or bipy (2) terminal ligands f…
Squaric Acid Mediated Synthesis and Biological Activity of a Library of Linear and Hyperbranched Poly(Glycerol)-Protein Conjugates
2012
Polymer-protein conjugates generated from side chain functional synthetic polymers are attractive because they can be easily further modified with, for example, labeling groups or targeting ligands. The residue specific modification of proteins with side chain functional synthetic polymers using the traditional coupling strategies may be compromised due to the nonorthogonality of the side-chain and chain-end functional groups of the synthetic polymer, which may lead to side reactions. This study explores the feasibility of the squaric acid diethyl ester mediated coupling as an amine selective, hydroxyl tolerant, and hydrolysis insensitive route for the preparation of side-chain functional, …
Squaric acid mediated chemoselective PEGylation of proteins: reactivity of single-step-activated α-amino poly(ethylene glycol)s.
2012
The covalent attachment of poly(ethylene glycol) (PEG) to therapeutically active proteins (PEGylation) has become an important method to deal with the pharmacological difficulties of these polypeptides, such as short body-residence times and immunogenicity. However, the derivatives of PEG used for PEGylation lack further functional groups that would allow the addition of targeting or labeling moieties. Squaric acid diethyl ester was used for the chemoselective single-step activation of poly(ethylene glycol)s into the respective ester amides. The resultant selective protein-reactive poly(ethylene glycol)s were investigated with respect to their selectivity towards amino acid residues in bovi…
Selective "one-pot" synthesis of functionalized cyclopentenones.
2012
Double addition (1,2-1,4) of vinyl magnesium bromide to squaric acid derivatives allows the preparation of polyoxygenated cyclopentenones (8) in a "one-pot" procedure. The reaction occurs through the intermediate formation of octatetraenes (6). Protonation of this latter intermediate at -78 °C with TFE occurs selectively at the vinyl CH(2) closer to the metallic centers. DFT studies of the cyclization step justify the observed diastereoselectivity.
Synthesis, Labeling and Preclinical Evaluation of a Squaric Acid Containing PSMA Inhibitor Labeled with 68 Ga: A Comparison with PSMA‐11 and PSMA‐617
2020
The L-lysine urea-L-glutamate (KuE) represents a key motif in recent diagnostic and therapeutic radiopharmaceuticals targeting the prostate specific membrane antigen (PSMA). Using a squaric acid moiety for coupling of KuE with a radioactive label, the squaric acid as a linker in the PSMA ligand seems to mimic the aromatic structure of the naphthylalanine unit on PSMA-617. In this work, we investigate the influence of squaric acid moiety on the biological activity of the compound carrying a KuE motif and three typical chelates. The derivatives TRAM.SA.KuE, DOTAGA.SA.KuE and NODAGA.SA.KuE were all synthesized in straightforward organic reactions and purified by HPLC afterward. Different amoun…
Extended conjugation in stilbenoid squaraines
2019
Abstract Squaraines, two-fold condensation products in 1,3-position of squaric acid, represent dyes or pigments of high actuality. After their first boom in electrophotography diverse applications are presently studied in a wide area of research, which reaches from electrooptical materials to biosensors and compounds used in photodynamic therapy. Absorption and/or emission ranges in the NIR are mandatory for many of these techniques. The present article deals with stilbenoid squaraines, which feature an extended conjugation in their biradicaloid D-π-A-π-D structure. Due to the charge-transfer character of the excitation, boundaries are set for the optimal length of the conjugation. The abso…