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The aim of this work was the investigation of novel organocatalysts for the Michael addition of diethyl malonate to β-nitrostyrene. The methodology of the study included NMR titration, reaction monitoring by NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS), product characterization by MALDI, IR spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and elemental analysis. As a result, evidence of supramolecular interactions between two pairs of components of the reaction was found. In addition to the supramolecular complexes, an unusual reaction, i.e., the Michael addition of NH-bispidines to β-nitrostyrene, was found, which led to previously unknown oligomers of β-nitrostyrene. A new mechanism for the catalytic action of NH-bispidine was proposed, which involved catalysis not by the initial organocatalyst but rather by its adduct with β-nitrostyrene. Thus, in this reaction, N-benzylbispidine acted as an initiator, and the real catalyst was the betaine formed during the initiation stage. [ABSTRACT FROM AUTHOR]

The aim of this work was the investigation of novel organocatalysts for the Michael addition of diethyl malonate to β-nitrostyrene. The methodology of the study included NMR titration, reaction monitoring by NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS), product characterization by MALDI, IR spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and elemental analysis. As a result, evidence of supramolecular interactions between two pairs of components of the reaction was found. In addition to the supramolecular complexes, an unusual reaction, i.e., the Michael addition of NH-bispidines to β-nitrostyrene, was found, which led to previously unknown oligomers of β-nitrostyrene. A new mechanism for the catalytic action of NH-bispidine was proposed, which involved catalysis not by the initial organocatalyst but rather by its adduct with β-nitrostyrene. Thus, in this reaction, N-benzylbispidine acted as an initiator, and the real catalyst was the betaine formed during the initiation stage.

Radioimmunotherapy (RIT) is a promising alternative to conventional treatment options. Here, we present experimental work on the synthesis, radiochemistry, and in vivo performance of a lanthanoid‐selective nonadentate bispidine ligand suitable for 177Lu3+ ion complexation. The ligand (bisp,1) was derivatised with a photoactivatable aryl azide (ArN3) group as a bioconjugation handle for light‐induced labelling of proteins. Quantitative radiosynthesis of [177Lu]Lu‐1+ was accomplished in 10 minutes at 40 °C. Subsequent incubation of [177Lu]Lu‐1+ with trastuzumab, followed by irradiation with light at 365 nm for 15 min, at room temperature and pH 8.0–8.3, gave the radiolabelled mAb, [177Lu]Lu‐1‐azepin‐trastuzumab ([177Lu]Lu‐1‐mAb) in a decay‐corrected radiochemical yield of 14 %, and radiochemical purity (RCP)>90 %. Stability studies and cellular binding assays in vitro using the SK‐OV‐3 human ovarian cancer cells confirmed that [177Lu]Lu‐1‐mAb remained biological active and displayed specific binding to HER2/neu. Experiments in immunocompromised female athymic nude mice bearing subcutaneous xenograft models of SK‐OV‐3 tumours revealed significantly higher tumour uptake in the normal group compared with the control block group (29.8±11.4 %ID g−1 vs. 14.8±6.1 %ID g−1, respectively; P‐value=0.037). The data indicate that bispidine‐based ligand systems are suitable starting points for constructing novel, high‐denticity chelators for specific complexation of larger radiotheranostic metal ion nuclides. [ABSTRACT FROM AUTHOR]

Introduction: The importance of the conformational behavior comprehension for proper prediction of properties for a certain compound or for a class of compounds is indisputable. For 3,7-diacylbispidines (3,7-diacyl-3,7-diazabicyclo[3.3.1]nonanes), only "double chair" (CC) conformers were prior found experimentally in the condensed phase, which differ only in the acyl groups relative orientation, "parallel," pa or "antiparallel," ap. However, 2 other conformer families, "boat-chair," BC and "double twist," TT, are known for other bicyclo[3.3.1]nonane derivatives. Features of these conformers would be useful for the accurate prediction of properties and activities of the compounds. Methods: Second-order perturbation theory ab initio techniques (MP2) in the triple-zeta correlation-consistent orbital basis set cc-pVTZ was employed to optimize the electronic energy for structures, to characterize the optimized structures as potential energy surface minima by energy hessian eigenvalue calculations and to calculate zero-point energy corrections for the minima using the "rigid rotor-harmonic oscillator" approximation to model the molecular ensemble thermodynamics. Additionally, the computational chemical thermodynamics benefits much from the concept of the molecular strain and its energy assessed successfully through the bond separation energy formalism. We combine both approaches in our investigation to find and consistently characterize the conformers previously unknown for the compounds under the studies. Results: Six possible conformers were found for the investigated 3,7-diacetyl-3,7-diazabicyclo[ 3.3.1]nonanes 1-4, formed by combining the skeletal conformation changes with the internal rotation of acyl substituents. The conformational behavior is quite similar for all investigated molecules. In all cases, the CC conformation is optimal for the bicyclic skeleton and ap orientation prevails over pa for 2 acetyl groups. This prevalence is 4-5 kcal mol-1 in CC and less than 1 kcal mol-1 in other skeletal forms, making rotation of 2 acyl groups in BC and TT almost independent. Concerning the skeletal conformations, the common energy sequence CC < BC < TT is found. While the relative BC energy is 6-7 kcal mol-1 over the optimal CC structure, TT forms are all strained by more than 12 kcal mol-1. Conclusions: For the first time, both BC and TT conformers of 3,7-diacetylbispidines were characterized by their strain and conformation energies together with known less strained CC forms. On the basis of our calculations, the relative energies of BC conformers are expected to be close to those of the CC acetyl amide bond rotamers found previously in experiment, therefore, their exclusion from the conformational behavior would look unjustified. On the contrary, TT conformers are found to be much more strained enough to be neglected in the conformational ensemble modeling. [ABSTRACT FROM AUTHOR]

A possibility of manifestation of the anomeric effect of the sp-hybridized carbon atom, which is a component of triple C≡C and C≡N bonds, was studied. The effect of carbon hybridization on the acceptor capacity of the carbon—carbon σ-bonds was evaluated. A high effective electronegativity of the sp-hybridized carbon atom was found to exert a noticeable effect on the magnitude of the anomeric interactions n N → σ ∗ CC . The triple bond in such systems indeed can participate in anomeric interactions, which was proved for N-propargyl substituted bispidines as an example using experimental (XRD) and computational methods. This participation is expressed in the stabilization of the bisectral conformation of the N—CH2—C≡CH and N—CH2—C≡N fragments in the case of N-monosubstituted and N,N′-disubstituted bispidines. The values of charge transfer from an unshared pair of nitrogen atoms to the σ-antibonding orbital of the C≡C—CH2 bond calculated for the model Me2N—CH2—X systems by the NBO method are up to 11.0 kcal mol−1, which is relatively low for the classical anomeric effect: the corresponding value for the N≡C—CH2 fragment is 11.3 kcal mol−1. The anomeric effect manifested by the acetylene group makes it possible to stabilize certain conformations in the bispidine systems containing propargyl substituents, which can affect the reactivity of acetylenes. For the N-benzyl systems (9.4 kcal mol−1) and N-allyl (9.4 kcal mol−1) and N-propyl (10.0 kcal mol−1) derivatives, the hyperconjugation stabilization is weaker and does not play a decisive role in conformational equilibrium. The obtained data are of obvious interest for specialists working in the field of the chemistry of the triple bond of the propargyl type. [ABSTRACT FROM AUTHOR]

The possibility of the complex formation of three bispidines with copper(ii) chloride and acetate in a deuterated DMF solution was studied by NMR titration. For all ligands, the formation of complexes with copper(ii) chloride was clearly detected based on the changes in the signals in the proton NMR spectra. The formation of complexes with copper(ii) acetate was not observed for any of the ligands. The results of the study can be used in the design of metal complex catalysts for the Henry reaction. [ABSTRACT FROM AUTHOR]

Polyamine (PA) catabolism is often reduced in cancer cells. The activation of this metabolic pathway produces cytotoxic substances that might cause apoptosis in cancer cells. Chemical compounds able to restore the level of PA catabolism in tumors could become potential antineoplastic agents. The search for activators of PA catabolism among bicyclononan-9-ones is a promising strategy for drug development. The aim of the study was to evaluate the biological activity of new 3,7-diazabicyclo[3.3.1]nonan-9-one derivatives that have antiproliferative properties by accelerating PA catabolism. Eight bispidine derivatives were synthetized and demonstrated the ability to activate PA catabolism in regenerating rat liver homogenates. However, only three of them demonstrated a potent ability to decrease the viability of cancer cells in the MTT assay. Compounds 4c and 4e could induce apoptosis more effectively in cancer HepG2 cells rather than in normal WI-38 fibroblasts. The lead compound 4e could significantly enhance cancer cell death, but not the death of normal cells if PAs were added to the cell culture media. Thus, the bispidine derivative 4e 3-(3-methoxypropyl)-7-[3-(1H-piperazin-1-yl)ethyl]-3,7-diazabicyclo[3.3.1]nonane could become a potential anticancer drug substance whose mechanism relies on the induction of PA catabolism in cancer cells. [ABSTRACT FROM AUTHOR]

[Display omitted] Two new potent AMPA receptor allosteric modulators, 6-(1,3-benzodioxol-5-yl)-1,11-dimethyl-3,6,9-triazatri-cyclo[7.3.1.13,11]tetradecane-4,8,12-trione and -4,8-dione were synthesized from 1,3-benzodioxol-5-amine and the corresponding 3,7-dichloroacetyl-3,7-diazabicyclo[3.3.1]-nonanes. In a wide concentration range (10−12–10−7 m), the 12-oxo derivative acts as a positive modulator causing the potentiation of the kainate-induced AMPA receptor currents with maximum potentiation at 1 nm (62%) while its analogue without a ketone group has significant (up to 40%) negative modulator effect. Their tentative mechanisms of action were analyzed by means of molecular modelling [ABSTRACT FROM AUTHOR]

The N-arylation of N-Boc-bispidine with arylboronic acids was accomplished under the copper-catalyzed Chan—Lam—Evans reaction conditions. The reaction products were characterized by NMR spectroscopy and X-ray diffraction. The characteristic features of the transannular N⋯N interaction were investigated by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Polyamine (PA) catabolism is often reduced in cancer cells. The activation of this metabolic pathway produces cytotoxic substances that might cause apoptosis in cancer cells. Chemical compounds able to restore the level of PA catabolism in tumors could become potential antineoplastic agents. The search for activators of PA catabolism among bicyclononan-9-ones is a promising strategy for drug development. The aim of the study was to evaluate the biological activity of new 3,7-diazabicyclo[3.3.1]nonan-9-one derivatives that have antiproliferative properties by accelerating PA catabolism. Eight bispidine derivatives were synthetized and demonstrated the ability to activate PA catabolism in regenerating rat liver homogenates. However, only three of them demonstrated a potent ability to decrease the viability of cancer cells in the MTT assay. Compounds 4c and 4e could induce apoptosis more effectively in cancer HepG2 cells rather than in normal WI-38 fibroblasts. The lead compound 4e could significantly enhance cancer cell death, but not the death of normal cells if PAs were added to the cell culture media. Thus, the bispidine derivative 4e 3-(3-methoxypropyl)-7-[3-(1H-piperazin-1-yl)ethyl]-3,7-diazabicyclo[3.3.1]nonane could become a potential anticancer drug substance whose mechanism relies on the induction of PA catabolism in cancer cells.

The reaction of 1,5-dimethyibispidin-9-one with acetone, acting as both a solvent and a reagent, affords 2,2,5,7-tetramethyl-1,3-diazaadamantan-6-one. The structure of the monohydrate of the target compound, which is a hydrogen-bonded supramolecular polymer, was determined by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Radioimmunotherapy (RIT) is a promising alternative to conventional treatment options. Here, we present experimental work on the synthesis, radiochemistry, and in vivo performance of a lanthanoid-selective nonadentate bispidine ligand suitable for 177 Lu 3+ ion complexation. The ligand (bisp,1) was derivatised with a photoactivatable aryl azide (ArN 3 ) group as a bioconjugation handle for light-induced labelling of proteins. Quantitative radiosynthesis of [ 177 Lu]Lu-1 + was accomplished in 10 minutes at 40 °C. Subsequent incubation of [ 177 Lu]Lu-1 + with trastuzumab, followed by irradiation with light at 365 nm for 15 min, at room temperature and pH 8.0-8.3, gave the radiolabelled mAb, [ 177 Lu]Lu-1-azepin-trastuzumab ([ 177 Lu]Lu-1-mAb) in a decay-corrected radiochemical yield of 14 %, and radiochemical purity (RCP)>90 %. Stability studies and cellular binding assays in vitro using the SK-OV-3 human ovarian cancer cells confirmed that [ 177 Lu]Lu-1-mAb remained biological active and displayed specific binding to HER2/neu. Experiments in immunocompromised female athymic nude mice bearing subcutaneous xenograft models of SK-OV-3 tumours revealed significantly higher tumour uptake in the normal group compared with the control block group (29.8±11.4 %ID g -1 vs. 14.8±6.1 %ID g -1 , respectively; P-value=0.037). The data indicate that bispidine-based ligand systems are suitable starting points for constructing novel, high-denticity chelators for specific complexation of larger radiotheranostic metal ion nuclides., (© 2023 Wiley-VCH GmbH.)

A number of new chiral bispidines containing monoterpenoid fragments have been obtained. The bispidines were studied as ligands for Ni-catalyzed addition of diethylzinc to chalcones. The conditions for chromatographic analysis by HPLC-UV were developed, in which the peaks of the enantiomers of all synthesized chiral products were separated, which made it possible to determine the enantiomeric excess of the resulting mixture. It was demonstrated that bispidine-monoterpenoid conjugates can be used as the ligands for diethylzinc addition to chalcone C=C double bond but not as inducers of chirality. Besides products of ethylation, formation of products of formal hydrogenation of the chalcone C=C double bond was observed in all cases. Note, that this formation of hydrogenation products in significant amounts in the presence of such catalytic systems was found for the first time. A tentative scheme explaining the formation of all products was proposed.

A number of chiral chelating conjugates combining a bispidine central backbone and one or two pinene side fragments were synthesized. It was shown for the first time that the synthesized compounds are capable to act as catalysts in the Henry reaction both individually and in the presence of metal salts. It was found that the best catalytic results were shown for bis-tertiary amine combining bispidinone and two (–)-myrtenol fragments, and copper as well as zinc acetates. [ABSTRACT FROM AUTHOR]

Bifunctional chelators as parts of modular metal‐based radiopharmaceuticals are responsible for stable complexation of the radiometal ion and for covalent linkage between the complex and the targeting vector. To avoid loss of complex stability, the bioconjugation strategy should not interfere with the radiometal chelation by occupying coordinating groups. The C9 position of the very stable CuII chelator 3,7‐diazabicyclo[3.3.1]nonane (bispidine) is virtually predestined to introduce functional groups for facile bioconjugation as this functionalisation does not disturb the metal binding centre. We describe the preparation and characterisation of a set of novel bispidine derivatives equipped with suitable functional groups for diverse bioconjugation reactions, including common amine coupling strategies (bispidine‐isothiocyanate) and the Cu‐free strain‐promoted alkyne–azide cycloaddition. We demonstrate their functionality and versatility in an exemplary way by conjugation to an antibody‐based biomolecule and validate the obtained conjugate in vitro and in vivo. [ABSTRACT FROM AUTHOR]

The goal of this work was to obtain novel ligands basedis on 1H-pyrazole-3(5)-carboxylic acids containing the triazole moiety at positions 3(6) or 4. Another goal was to study the possibility of joining pyrazole carboxylic acid fragments with various framework structures to create polychelated ligands that can be used in medicinal chemistry and metal complex catalysis. Methods have been developed for the synthesis of previously unknown N-unsubstituted 5- and 4-azido-1H-pyrazole-3-carboxylic acids from the corresponding available amino derivatives in high yields. For the first time, the joining of bispidines to azoles was carried out using the copper-catalyzed [3+2] cycloaddition reaction. [ABSTRACT FROM AUTHOR]

Investigations on the relative energy of two least-strain conformers for bicyclo[3.3.1]nonane 1, bicyclo[3.3.1]nonan-9-one 2, and their heteroanalogues: 3,7-dimethyl-3,7-diazabicyclo[3.3.1]nonane 3, 3,7-dimethyl-3,7-diazabicyclo[3.3.1]nonan-9-one 4 were performed using the calculations from the first principles (ab initio, DFT) as well as by semiempirical (NDDO, DFTB) and empirical (molecular mechanics, MM) techniques. For these quite simple structures, serious discrepancies in results of modeling between methods of different origins were revealed. Nonempirical calculations state that the "double chair" (CC) form is the most favorable for carbobicyclic structures 1 and 2, while 3,7-dimethyl-3,7-diaza compounds 3 and 4 are in general more prone to adopt the "chair-boat" (CB) conformation. The classical rationalization of these quantum chemistry results leads to the hypothesis similar to one that underlies the Gillespie VSEPR concept, namely that the 3,7-repulsion of lone electron pairs is stronger than the corresponding interaction of hydrogen atoms of C-H bonds. The semiempirical NDDO calculations retain the qualitative correspondence of the results to those of the ab initio calculations, while the results of more recent DFTB approaches are closer to MM in their qualitative inconsistency with high-level ab initio methods. In particular, for 4 the relative energy of CC is severely underestimated, erroneously predicting the predominance of this form over CB. The origin of this failure could lie in the relatively coarse parameterization of common force fields when concerning the subtle interplay between different types of interatomic interactions and could be recovered, although only partially, by the proper choice of the charge scheme to use the atomic-centered charges in the explicit account for the non-valency interactions in the Coulombic form. [ABSTRACT FROM AUTHOR]

1,5-Dimethylbispidinone (1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonan-9-one) reacts with natural ketones, including optically active ones, to give new aminal-type compounds combining diazaadamantane and aliphatic fragments. [ABSTRACT FROM AUTHOR]

The coordination chemistry of the hexadentate bispidine ligand L1 with three pyridine, one pyridazine, and two tertiary amine donors with CuII and ZnII is reported. The substitution of one of the two cis-disposed pyridine donors in-plane with the two tertiary amines of the bispidine backbone by a pyridazine group was predicted to substantially reduce distortion from planarity of the tetradentate subunit and therefore was assumed to lead to higher CuII complex stability. The X-ray single-crystal structures of the ZnII and CuII complexes, which are in excellent agreement with the DFT- and MM-optimized structures, confirmed this prediction but indicated that deviation from planarity is appreciable. This also emerges from solution spectroscopy (UV/Vis/NIR and EPR of the CuII complex), which indicated that the in-plane ligand field is only slightly increased. The geometric parameters together with the lower basicity of pyridazine versus pyridine (pKa=2.33 vs. 5.23) are also in agreement with an only slightly more negative redox potential of the CuII/I couple (E0=-780 vs. -760 mV, MeCN, vs. Fc/Fc+), and the potentiometrically determined CuII stability constant with L1 is slightly lower than that with the parent ligand L2 (log K=12.7 vs. 14.5). Therefore, modification of the donor groups is a more promising approach to increasing the stabilities of these complexes and yields 64CuII chelators that outperform known hexadentate bispidine ligands. [ABSTRACT FROM AUTHOR]

The acylation of unsymmetrical N-benzylbispidinols in aromatic solvents without an external base led to the formation of supramolecular gels, which possess different thicknesses and degrees of stability depending on the substituents in para-positions of the benzylic group as well as on the nature of the acylating agent and of the solvent used. Structural features of the native gels as well as of their dried forms were studied by complementary techniques including Fourier-transform infrared (FTIR) and attenuated total reflection (ATR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering and diffraction (SAXS). Structures of the key crystalline compounds were established by X-ray diffraction. An analysis of the obtained data allowed speculation on the crucial structural and condition factors that governed the gel formation. The most important factors were as follows: (i) absence of base, either external or internal; (ii) presence of HCl; (iii) presence of carbonyl and hydroxyl groups to allow hydrogen bonding; and (iv) presence of two (hetero)aromatic rings at both sides of the molecule. The hydrogen bonding involving amide carbonyl, hydroxyl at position 9, and, very probably, ammonium N-H+ and Cl− anion appears to be responsible for the formation of infinite molecular chains required for the first step of gel formation. Subsequent lateral cooperation of molecular chains into fibers occurred, presumably, due to the aromatic π−π-stacking interactions. Supercritical carbon dioxide drying of the organogels gave rise to aerogels with morphologies different from that of air-dried samples.

The aminomethylation reaction of 9-benzyl-2,4-dioxo-3,9-diazaspiro[5.5]undecane-1,5-dicarbonitrile hydrochloride in the presence of primary aliphatic amines and an excess of 37% aqueous formaldehyde led to the formation of 7-substituted 1'-benzyl-2,4-dioxo-1 H,5 Hspiro[3,7-diazabicyclo[3.3.1]nonane-9,4'-piperidine]-1,5-dicarbonitrile derivatives. [ABSTRACT FROM AUTHOR]

A new (C,N,N)-pincer cyclopalladate unsymmetrical complex of 3-benzyl-7-methyl-3,7-diazabicyclo[3.3.1]nonane (3-benzyl-7-methylbispidine) was synthesized and characterized. Catalytic performance of this complex was examined in the Heck and Suzuki reactions and in the norbornene hydroarylation. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] The structure of reaction products obtained from 3,5-dicyano-4,4-dimethyl-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates, primary amines, and formaldehyde substantially depends on the nature of counter-ion (morpholinium or N-methylmorpholinium), as well as on the primary amine structure and the ratio of reactants. Aminomethylation of these thiolates with highly nucleophilic amines RCHNH and excess formalin (2 equiv and more) produced 7-RCH-9,9-dimethyl-2-oxo-4-thioxo-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarbonitrile salts, which gave the respective bispidines upon acidification. Performing this reaction with aromatic amines in the case of N-methylmorpholinium 3,5-dicyano-4,4-dimethyl-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolate led to analogous bispidines, while the morpholinium salt gave 3-aryl-8,8-dimethyl-7-[(morpholin-4-yl)methyl]-6-oxo-3,4,7,8-tetrahydro-2 H,6 H-pyrido[2,1- b][1,3,5]thiadiazine-7,9-dicarbonitriles. The treatment of thiolates with 1 equiv of НСНО and 1 equiv of RCHNH led to 7-RCH-4-amino-9,9-dimethyl-2-oxo-6-thioxo-3,7-diazabicyclo[3.3.1]non-3-ene-1-carbonitriles. The molecular and crystal structures of key compounds were studied in detail by X-ray structural analysis. [ABSTRACT FROM AUTHOR]

The lithiation-trapping of an N-Boc bispidine-ketal using s-BuLi/TMEDA has been studied. Key findings include an activating effect of the 4-ketal group on the lithiation and complete diastereoselectivity with methylation and Cu-mediated allylation. In contrast, reduced diastereoselectivity was noted for direct allylation and silylation; mechanistic explanations are proposed. [ABSTRACT FROM AUTHOR]

The efficient transformation of the hexadentate bispidinol 1 into carbamate derivatives yields functional bispidines enabling convenient functionalization for targeted imaging. The BODIPY-substituted bispidine 3 combines a coordination site for metal ions, such as radioactive 64CuII, with a fluorescent unit. Product 3 was thoroughly characterized by standard analytical methods, single crystal X-ray diffraction, radiolabeling, and photophysical analysis. The luminescence of ligand 3 was found to be strongly dependent on metal ion coordination: CuII quenches the BODIPY fluorescence, whereas NiII and ZnII ions do not affect it. It follows that, in imaging applications with the positron emitter 64CuII, residues of its origin from enriched 64Ni and the decay products 64NiII and 64ZnII, efficiently restore the fluorescence of the ligand. This allows for monitoring of the emitted radiation as well as the fluorescence signal. The stability of the 64CuII-3 complex is investigated by transmetalation experiments with ZnII and NiII, using fluorescence and radioactivity detection, and the results confirm the high stability of 64CuII-3. In addition, metal complexes of ligand 3 with the lanthanide ions TbIII, EuIII, and NdIII are shown to exhibit emission of the BODIPY ligand and the lanthanide ion, thus enabling dual emission detection. [ABSTRACT FROM AUTHOR]

A new supramolecular synthon, a 2L: 1M complex of bidentate bispidine with transition metal, was suggested. A number of complex compounds of 1,5-dimethylbispidin-9-one with Cu, Ni, and Co salts (perchlorates, chlorides, bromides, nitrates, trifluoroacetates) were synthesized. The structure and composition of complexes obtained were estimated based on the combination of physicochemical methods of analysis (elemental analysis, X-ray diffraction analysis, NMR, IR, and Raman spectroscopy, electron absorption spectroscopy, ESI mass spectrometry, CVA). The composition of most complexes in the solid state corresponds to the formula MLX, and in a number of cases the fragment [ML] is retained in solution, which was shown by NMR spectroscopy for nickel complexes and by mass spectrometry for copper complexes. In the case of copper chloride, the composition of the acetonitrile solutions in the presence of the ligand depends on the ratio of starting compounds and their concentration: an increase in proportion of CuCl and concentration shifts the equilibrium to the side of complexes with higher nuclearity. A 2L: 1M complex of bispidine with metal was for the first time structurally characterized using copper( ii) nitrate derivative as an example. The CVA method showed existence of reversible electrochemical reduction of the metal for a number of complexes (the products of the reaction of 1,5-dimethylbispidin-9-one with nickel( ii) and cobalt( ii) chlorides, as well as with nickel( ii) bromide). According to the IR and Raman spectra, chelation of metals with 1,5-dimethylbispidin-9-one leads to the shift of the absorption band of the ligand carbonyl group from 1700 to 1721-1744 cm. Nickel( ii) and copper( ii) perchlorates and nitrates were concluded to be the most promising complexation agents for the binding of two NH,NH-bispidine ligands in a coordination polymer. [ABSTRACT FROM AUTHOR]

A bicyclic ligand platform for iron(II), which allows total control over the complex's magnetic properties in aqueous solution simply by varying one of the six coordination sites of the bispidine ligand, is reported. To achieve this, an efficient synthetic route to an N5 bispidine framework (ligand L4) that features an unsubstituted N-7 site is established. Then, by choosing appropriate N-7-coordinating substituents, the spin state of choice can be imposed on the corresponding ferrous complexes under environmentally relevant conditions in water and near-room temperature. Importantly, the first low-spin and diamagnetic iron(II) chelates in the bispidine series, both in the solid state and in aqueous solution, are reported. The eradication of head-on steric clashes between pendent coordinating arms is at the origin of this success. A new pair of constitutionally similar ferrous coordination compounds of a multidentate ligand system is obtained, which exhibits a distinctly binary (off-on) magnetic relationship. The new synthetic intermediate L4 may be substituted in just one step by any desired pendent arm, thus allowing access to complexes with finely tuned magnetic properties. [ABSTRACT FROM AUTHOR]

A number of new chiral bispidines containing monoterpenoid fragments have been obtained. The bispidines were studied as ligands for Ni-catalyzed addition of diethylzinc to chalcones. The conditions for chromatographic analysis by HPLC-UV were developed, in which the peaks of the enantiomers of all synthesized chiral products were separated, which made it possible to determine the enantiomeric excess of the resulting mixture. It was demonstrated that bispidine-monoterpenoid conjugates can be used as the ligands for diethylzinc addition to chalcone C=C double bond but not as inducers of chirality. Besides products of ethylation, formation of products of formal hydrogenation of the chalcone C=C double bond was observed in all cases. Note, that this formation of hydrogenation products in significant amounts in the presence of such catalytic systems was found for the first time. A tentative scheme explaining the formation of all products was proposed. [ABSTRACT FROM AUTHOR]

The article discusses the first example of 3,7-diazabicyclo[3.3.1]nonane synthesis by aminomethylation of Guareschi imide salts. It states that 2,6-Dioxopiperidine-3,5-dicarbonitriles, also known as Guareschi imides and salts are prepared by condensation of cyanoacetic ester, ketones, and ammonia. It mentions that the reaction of 3-aryl-2-cyanoacrylamides with cyanoacetylpyrazole serves as the first example of 3,7-diazabicyclo[3.3.1]nonane derivatives synthesis.

Cover Feature: Versatile Bispidine-Based Bifunctional Chelators for 64CuII-Labelling of Biomolecules (Chem. Eur. J. 9/2020) Reductive alkylation at the relatively inert C9-position of bispidols paves the way for generating a number of derivatives ready to be coupled to a variety of targeting vector molecules. As these bispidine derivatives form highly stable complexes with the positron emitter SP 64 sp Cu SP II sp , they are virtually predestined for their application in the field of diagnostic positron emission tomography (PET). [Extracted from the article]

Bifunctional chelators as parts of modular metal-based radiopharmaceuticals are responsible for stable complexation of the radiometal ion and for covalent linkage between the complex and the targeting vector. To avoid loss of complex stability, the bioconjugation strategy should not interfere with the radiometal chelation by occupying coordinating groups. The C9 position of the very stable Cu II chelator 3,7-diazabicyclo[3.3.1]nonane (bispidine) is virtually predestined to introduce functional groups for facile bioconjugation as this functionalisation does not disturb the metal binding centre. We describe the preparation and characterisation of a set of novel bispidine derivatives equipped with suitable functional groups for diverse bioconjugation reactions, including common amine coupling strategies (bispidine-isothiocyanate) and the Cu-free strain-promoted alkyne-azide cycloaddition. We demonstrate their functionality and versatility in an exemplary way by conjugation to an antibody-based biomolecule and validate the obtained conjugate in vitro and in vivo., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The acylation of unsymmetrical N-benzylbispidinols in aromatic solvents without an external base led to the formation of supramolecular gels, which possess different thicknesses and degrees of stability depending on the substituents in para-positions of the benzylic group as well as on the nature of the acylating agent and of the solvent used. Structural features of the native gels as well as of their dried forms were studied by complementary techniques including Fourier-transform infrared (FTIR) and attenuated total reflection (ATR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering and diffraction (SAXS). Structures of the key crystalline compounds were established by X-ray diffraction. An analysis of the obtained data allowed speculation on the crucial structural and condition factors that governed the gel formation. The most important factors were as follows: (i) absence of base, either external or internal; (ii) presence of HCl; (iii) presence of carbonyl and hydroxyl groups to allow hydrogen bonding; and (iv) presence of two (hetero)aromatic rings at both sides of the molecule. The hydrogen bonding involving amide carbonyl, hydroxyl at position 9, and, very probably, ammonium N-H+ and Cl− anion appears to be responsible for the formation of infinite molecular chains required for the first step of gel formation. Subsequent lateral cooperation of molecular chains into fibers occurred, presumably, due to the aromatic π−π-stacking interactions. Supercritical carbon dioxide drying of the organogels gave rise to aerogels with morphologies different from that of air-dried samples. [ABSTRACT FROM AUTHOR]

The coordination chemistry of the hexadentate bispidine ligand L 1 with three pyridine, one pyridazine, and two tertiary amine donors with Cu II and Zn II is reported. The substitution of one of the two cis-disposed pyridine donors in-plane with the two tertiary amines of the bispidine backbone by a pyridazine group was predicted to substantially reduce distortion from planarity of the tetradentate subunit and therefore was assumed to lead to higher Cu II complex stability. The X-ray single-crystal structures of the Zn II and Cu II complexes, which are in excellent agreement with the DFT- and MM-optimized structures, confirmed this prediction but indicated that deviation from planarity is appreciable. This also emerges from solution spectroscopy (UV/Vis/NIR and EPR of the Cu II complex), which indicated that the in-plane ligand field is only slightly increased. The geometric parameters together with the lower basicity of pyridazine versus pyridine (pK a =2.33 vs. 5.23) are also in agreement with an only slightly more negative redox potential of the Cu II/I couple (E o =-780 vs. -760 mV, MeCN, vs. Fc/Fc + ), and the potentiometrically determined Cu II stability constant with L 1 is slightly lower than that with the parent ligand L 2 (log K=12.7 vs. 14.5). Therefore, modification of the donor groups is a more promising approach to increasing the stabilities of these complexes and yields 64 Cu II chelators that outperform known hexadentate bispidine ligands., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)