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1.
Mol Divers ; 17(3): 471-7, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23636682

RESUMO

An efficient solution-phase parallel synthesis of alkylated guanidines from commercial thioisocyanates and amines is described. In the first step, a thioisocyanate reacts with one equivalent of ammonia or a primary or secondary amine to give a thiourea intermediate. The latter is S-alkylated with n-dodecyl bromide resulting in the corresponding thiouronium bromide. Finally, the reaction of the thiouronium salt with a second equivalent of ammonia or a primary amine yields an alkylated guanidine. All three synthetic steps are easily combined in a one-pot high-yielding procedure with a simple work-up. Ca. 250 guanidine derivatives with high structural and functional diversity were synthesized by the developed method. 35 representatives reported in this study were fully characterized.


Assuntos
Aminas/metabolismo , Guanidinas/síntese química , Isocianatos/metabolismo , Aminas/química , Catálise , Guanidinas/química , Guanidinas/metabolismo , Isocianatos/química , Estrutura Molecular
2.
J Chem Inf Model ; 50(4): 470-9, 2010 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-20297844

RESUMO

A database of 7.9 million compounds commercially available from 29 suppliers in 2008-2009 was assembled and analyzed. 5.2 million structures of this database were identified to be unique and were subjected to an assessment of physical and biological properties and estimation of molecular diversity. The rules of Lipinski and Veber were applied to the molecular weight, the calculated water/n-octanol partition coefficients (Clog P), the calculated aqueous solubility (log S), the numbers of hydrogen-bond donors and acceptors, and the calculated Caco-2 membrane permeability to identify the drug-like compounds, whereas the toxicity/reactivity filters were used to remove the structures with biologically undesired functional groups. This filtering resulted in 2.0 million (39%) structures perfectly suitable for high-throughput screening of biological activity. Modified filters applied to identify lead-like structures revealed that 16% of the unique compounds could be potential leads. Assessment of the biological activities, the analysis of diversity, and the sizes of exclusive sets of compounds are presented.


Assuntos
Bases de Dados Factuais , Compostos Orgânicos/química , Compostos Orgânicos/provisão & distribução , Preparações Farmacêuticas/química , Preparações Farmacêuticas/provisão & distribução , Avaliação Pré-Clínica de Medicamentos , Compostos Orgânicos/metabolismo , Compostos Orgânicos/farmacologia , Relação Estrutura-Atividade
3.
Proc Natl Acad Sci U S A ; 106(27): 10922-7, 2009 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-19549870

RESUMO

A detailed single-crystal X-ray study of conformationally flexible sulfonimide-based dendritic molecules with systematically varied molecular architectures was undertaken. Thirteen crystal structures reported in this work include 9 structures of the second-generation dendritic sulfonimides decorated with different aryl groups, 2 compounds bearing branches of both second and first generation, and 2 representatives of the first generation. Analysis of the packing patterns of 9 compounds bearing second-generation branches shows that despite their lack of strong directive functional groups there is a repeatedly reproduced intermolecular interaction mode consisting in an anchor-type packing of complementary second-generation branches of neighbouring molecules. The observed interaction tolerates a wide range of substituents in meta- and para-positions of the peripheral arylsulfonyl rings. Quantum chemical calculations of the molecule-molecule interaction energies agree at the qualitative level with the packing preferences found in the crystalline state. The calculations can therefore be used as a tool to rationalize and predict molecular structures with commensurate and non-commensurate branches for programming of different packing modes in crystal.

4.
Angew Chem Int Ed Engl ; 48(6): 1030-69, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19130514

RESUMO

In light of the considerable impact synthetic 2D polymers are expected to have on many fundamental and applied aspects of the natural and engineering sciences, it is surprising that little research has been carried out on these intriguing macromolecules. Although numerous approaches have been reported over the last several decades, the synthesis of a one monomer unit thick, covalently bonded molecular sheet with a long-range ordered (periodic) internal structure has yet to be achieved. This Review provides an overview of these approaches and an analysis of how to synthesize 2D polymers. This analysis compares polymerizations in (initially) a homogeneous phase with those at interfaces and considers structural aspects of monomers as well as possibly preferred connection modes. It also addresses issues such as shrinkage as well as domain and crack formation, and briefly touches upon how the chances for a successful structural analysis of the final product can possibly be increased.

5.
Chemphyschem ; 10(1): 265-9, 2009 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-19035606

RESUMO

Novel dendrimers G2PC and G4PC consisting of a p-pentaphenylene core (PC) appended in the para position with two second-generation (G2) or two fourth-generation (G4) sulfonimide branches and two n-octyl chains, as well as a model compound of the pentaphenylene core (G0PC), are prepared. The photophysical properties (absorption, emission, and excitation spectra; fluorescence decay lifetime; and fluorescence anisotropy spectra) of the three compounds are investigated under different experimental conditions (dichloromethane solution and solid state at 293 K, dichloromethane/methanol rigid matrix at 77 K). In the absorption spectra contributions from both the branches and the core can be clearly identified. The fluorescence spectra show only the characteristic fluorescence of the pentaphenylene unit with lambda(max) around 410 nm in fluid solution and 420 nm in the solid state. In solution the fluorescence quantum yields are 0.78, 0.76, and 0.72 for G0PC, G2PC, and G4PC, respectively, and the fluorescence lifetime is about 0.7 ns in all cases. Energy transfer from the chromophoric groups of the dendrimer branches to the core does not occur. The three compounds show the same, high steady-state anisotropy value (0.35) in dilute rigid-matrix solution at 77 K. In dichloromethane at 293 K, the increasing anisotropy values along the series G0PC (0.17), G2PC (0.27), and G4PC (0.32), with increasing molecular volume of the three compounds, show that depolarization takes place by molecular rotation. In the solid state the anisotropy is very low (0.015, 0.017, and 0.035 for G0PC, G2PC, and G4PC, respectively), probably because of fast depolarization via energy migration.

6.
Chemistry ; 14(34): 10797-807, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18942696

RESUMO

We report the synthesis of molecular sheets based on the photochemically initiated dimerization of monomers with lateral anthracene units. The film thickness and composition were investigated by ellipsometry and X-ray photoelectron spectroscopy (XPS). The mechanical stability of the film was sufficient to span it over 45x45 microm-sized holes. Several model reactions were performed to illustrate the underlying chemistry and to assist in analysis. The reported experiments are considered first steps towards the ultimate goal of the rational synthesis of laterally "infinite", one-monomer-unit-thick molecular sheets with a long-range positional order and a periodic covalent-bonding pattern. Such sheets are referred to as 2D polymers and are considered a prime goal of chemical synthesis with intriguing applications.


Assuntos
Ar , Antracenos/síntese química , Membranas Artificiais , Água/química , Antracenos/química , Dimerização , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Tamanho da Partícula , Fotoquímica , Espectrofotometria , Propriedades de Superfície , Raios X
7.
J Org Chem ; 73(9): 3562-5, 2008 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-18358000

RESUMO

Systematic analysis of the persulfonylation of branched aromatic oligoamines with different arylsulfonyl chlorides allowed optimization of the repetitive steps involved in the synthesis of the sulfonimide-based dendrimers. The optimized procedures afforded the fourth generation N- and pentaphenylene-centered dendrimers with 16 and 32 peripheral groups, respectively. Analysis of products of incomplete substitution showed that the amino groups in aromatic oligoamines are persulfonylated consecutively.


Assuntos
Aminas/química , Dendrímeros/síntese química , Compostos de Enxofre/síntese química , Dendrímeros/química , Estrutura Molecular , Compostos de Enxofre/química
8.
J Phys Chem B ; 111(24): 6620-7, 2007 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-17408257

RESUMO

We have investigated the fluorescence properties of dendrimers (Gn is the dendrimer generation number) containing four different luminophores, namely terphenyl (T), dansyl (D), stilbenyl (S), and eosin (E). In the case of T, the dendrimers contain a single p-terphenyl fluorescent unit as a core with appended sulfonimide branches of different size and n-octyl chains. In the cases of D and S, multiple fluorescent units are appended in the periphery of poly(propylene amine) dendritic structures. In the case of E, the investigated luminophore is noncovalently linked to the dendritic scaffold, but is encapsulated in cavities of a low luminescent dendrimer. Depending on the photophysical properties of the fluorescent units and the structures of the dendrimers, different mechanisms of fluorescence depolarization have been observed: (i) global rotation for GnT dendrimers; (ii) global rotation and local motions of the dansyl units at the periphery of GnD dendrimers; (iii) energy migration among stylbenyl units in G2S; and (iv) restricted motion when E is encapsulated inside a dendrimer, coupled to energy migration if the dendrimer hosts more than one eosin molecule.

9.
Photochem Photobiol Sci ; 6(4): 471-9, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17404643

RESUMO

We report the photophysical properties (absorption and emission spectra, quantum yield, and lifetime) of five dendrimers of first generation based on a TREN (tris(2-aminoethyl)amine) skeleton functionalized at the periphery with naphthyl and/or 5-dimethylamino-1-naphthalenesulfonamide (hereafter called dansyl) chromophores. Each dendrimer comprises one tertiary amine unit in the core and three branches carrying a sulfonimido unit at the periphery, each one substituted by two identical or different moieties. In particular, TD6 and TN6 contain dansyl (D) or naphthyl (N) units, respectively, while TD3B3, TN3B3 and TN3D3 contain dansyl, naphthyl or benzyl (B) units at the periphery. The spectroscopic behaviour of these dendrimers has been investigated in acetonitrile solution and compared with that of reference compounds. For all dendrimers the absorption bands are red shifted compared to those of monomeric naphthyl and dansyl reference compounds. Moreover, the intense naphthyl and dansyl fluorescence is greatly quenched because of strong interactions between the two aromatic moieties linked by a sulfonimido unit. Protonation of the amine units of the dendrimers by addition of CF(3)SO(3)H (triflic) acid causes a decrease in intensity of the luminescence and a change in the shape of the emission bands. The shapes of the titration curves depend on the dendrimer, but in any case the effect of acid can be fully reversed by successive addition of base (tributylamine). The obtained results reveal that among the intradendrimer interactions the most important one is that taking place (via mesomeric interaction) between the various chromophores and a pair of sulfonimido groups.

10.
Chemphyschem ; 7(9): 1980-4, 2006 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-16900563

RESUMO

The photophysical properties of three dendrimers containing a p-terphenyl core with appended sulfonimide branches of different size and n-octyl chains have been investigated in dichloromethane solution. In the dendrimer absorption spectra contributions from both the branches and the core are clearly identified. The fluorescence spectra show only the characteristic fluorescence of the terphenyl unit. Energy transfer from the appended chromophoric groups to the core does not occur. In the dendrimers, the terphenyl core exhibits a very high fluorescence quantum yield (ca. 0.75) and a short emission lifetime (0.8 ns). These properties allowed investigations of the fluorescence depolarization caused by rotation of the dendrimers. The dendrimers show a very high steady-state anisotropy in dichloromethane solution at room temperature (0.24 for the largest one), compared to that of the parent terphenyl under the same experimental conditions (<0.01) and in rigid matrix (0.33). Both the n-octyl chains and the sulfonimide branches play important roles to slow down the molecular rotation.


Assuntos
Físico-Química/métodos , Fotoquímica/métodos , Espectrofotometria/métodos , Compostos de Sulfônio/química , Compostos de Terfenil/química , Anisotropia , Dendrímeros , Luz , Cloreto de Metileno/química , Modelos Químicos , Conformação Molecular , Estrutura Molecular , Espectrometria de Fluorescência , Temperatura , Fatores de Tempo
11.
J Am Chem Soc ; 128(27): 8964-74, 2006 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-16819893

RESUMO

The synthesis of "designer" dendrimers and dendrons with sulfonimide units at every branching point is reported. The synthesis is based on a series of (regio)selective functionalization reactions of amines and sulfonamides allowing precise control of the dendrimers' shape, the number of branches in each generation, and their peripheral decoration with functional groups. In principle, structurally different branches can be incorporated at any position within the dendrimer structure at will. Structurally perfect symmetrical and two-faced "Janus"-type dendrimers, as well as dendrimers and dendrons with intended interstices were synthesized on a preparative scale and fully characterized. Oligosulfonimide dendrons of various generations bearing an aryl bromide functional group at their focal points were attached to a p-phenylene core with the aid of Suzuki cross-coupling reactions resulting in dendrimers with photoactive terphenyl cores. The structure and the high purity of all dendritic sulfonimides were confirmed by means of (1)H and (13)C NMR, electrospray ionization mass spectrometry (ESI-MS), and elemental analysis. The utility of MALDI-TOF mass spectrometry for the analytical characterization of these dendrimers was evaluated in comparison to electrospray ionization. Two model branched oligosulfonimides were characterized in the solid state by single-crystal X-ray analysis. Reaction selectivities and conformation of sulfonimide branching points were rationalized by DFT calculations.

12.
J Phys Chem A ; 110(30): 9405-10, 2006 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-16869690

RESUMO

The potential stabilization of normally unstable C20, the smallest fullerene, via its encapsulation inside a tetraureacalix[4]arene dimer has been analyzed using molecular mechanics calculations with different force fields, the self-consistent-charge density-functional tight-binding with dispersion correction (SCC-DFTB-D) model, and standard density-functional-theory (DFT) calculations. The interaction energies obtained for the C20 complex have been compared with analogous values calculated for numerous complexes of the tetraureacalix[4]arene dimer with other guests. Results of the calculations with all force fields and SCC-DFTB-D predict that the binding of C20 occurs with the highest selectivity. On the other hand, standard DFT calculations fail to correctly describe the stabilization of the complexes under study as standard DFT generally does not treat dispersion interactions properly. Predicted relative stabilities of the complexes are discussed in conjunction with available experimental data. Molecular dynamics simulations reveal the instability of the guest-free capsular dimer, which decomposes on a 1-ns time scale, while dimeric complexes with guests remained intact during the 5-ns simulation time, indicating the guest-driven formation of the molecular capsule.

13.
Chemistry ; 12(22): 5685-90, 2006 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-16721887

RESUMO

A series of amide-based molecular knots equipped selectively with fluorescent dansyl and/or pyrenesulfonyl moieties were synthesized from the readily available tris(allyloxy)knotane. UV/Vis absorption spectra, emission spectra, and the emission lifetimes of the fluorescent knotanes were investigated in chloroform at 298 K. The absorption spectra of the knotanes correspond to those of mixtures of their UV-active constituents. The fluorescence quantum yields and lifetimes of the dansyl and pyrenesulfonyl moieties are partly quenched by the knotane platform. In the KN(Da)(2)(Py) species, the fluorescent excited state of the dansyl units (lambda(max)=510 nm) lies at lower energy than the fluorescent excited state of the pyrenesulfonyl unit (lambda(max)=385 nm), the emission of which is accordingly quenched with sensitization of the dansyl fluorescence. In the KN(Ao)(2)(Da), KN(Ao)(Da)(2), and KN(Da)(3) species, the addition of acids causes the protonation of their dansyl units with a consequent decrease in the intensity of the dansyl band at 510 nm and appearance of the emission band of the protonated dansyl unit (lambda(max)=340 nm). Each dansyl unit of KN(Ao)(Da)(2) and KN(Da)(3) undergoes the independent protonation. In these incompletely protonated knotanes the fluorescence of the protonated dansyl units is partly quenched by nonprotonated ones. These processes can be quantitatively reversed upon addition of a base. In KN(Da)(2)(Py), an increase of the fluorescence of its pyrenesulfonyl group is observed when the dansyl groups are protonated. The results obtained show that the readily available and easily functionalizable amide-knotanes can be used as an interesting scaffold to obtain fluorescent switches.

14.
Chemistry ; 11(19): 5625-36, 2005 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-16034993

RESUMO

Mass spectrometry, in particular MALDI-MS, has often been used as a valuable means to characterize dendritic molecules with respect to their molecular masses. Also, it is a valuable tool for analyzing potential defects in their structure which result from incomplete synthetic steps. This article presents a comparison of ESI and MALDI mass spectrometric experiments on dendrimers persulfonylated at their periphery. While the ESI mass spectra easily permit impurities and defects to be identified and thus provide evidence for sample purity, reactions with acidic matrices occur during the MALDI process. The resulting defects are identical to those expected from incomplete substitution. Thus, in these cases, MALDI-MS yields false negative results. With mass-selected, ESI-generated ions, collision experiments were performed in an FT-ICR mass spectrometer cell to provide detailed insight into the fragmentation patterns of the various dendrimers. Different fragmentation patterns are observed depending on the exact structure of the dendrimer. Also, the nature of the charge is important. The fragmentation reactions for protonated species differ much from those binding a sodium or potassium ion. These differences can be traced back to different sites for binding H+ versus Na+ or K+. Tandem MS experiments on mass-selected dendrimer ions with defects can be used to distinguish different types of defects. A concise structural assignment can thus be made on the basis of these experiments. Even mixtures of two isobaric defect variants with the same elemental composition can be identified.

15.
Angew Chem Int Ed Engl ; 44(10): 1456-77, 2005 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-15704147

RESUMO

How and why do molecules tangle or thread? Investigations of molecular knots (knotanes) may shed some light on the mechanisms of (supra)molecular templation and the folding of molecules that result in intertwining. The topological chirality of these fascinating molecules leads to new types of isomerism and paves the way to nanosized molecular motors. Their preparation and derivatization makes high demands on modern synthetic methods and analytical separation since molecular knots are formed in a more or less planned design based on metal coordination or hydrogen-bonding patterns. This Review describes the development of templation techniques for the synthesis of knotanes and their chiral resolution as well as their selective functionalization and use as building blocks in the synthesis of higher knotane assemblies. Such assemblies can possess linear, branched, or even macrocyclic structures which, on the one hand, introduce unprecedented isomeric compositions that arise from multiple topological stereogenic units and, on the other, define new types of artificial macromolecules beyond polymers and dendritic species.

16.
Chemistry ; 10(11): 2804-10, 2004 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-15195311

RESUMO

Selectively functionalized molecular knots (knotanes) of the amide-type have been used as building blocks in syntheses of higher covalent assemblies composed of up to four knotane units. Preparation of linear and branched tetraknotanes consisted of the consecutive selective removal of allyl groups followed by linking of the intermediate hydroxyknotanes with biphenyl-4,4'-disulfonyl chloride. Macrocyclic knotane oligomers involving two, three, and four knotane moieties were obtained by high-dilution cyclization of dihydroxyknotane and biphenyl-4,4'-disulfonyl chloride. Due to their relation with cyclophanes, the latter class of oligomeric knotanes was termed "knotanophanes". Chiral resolution analysis of new oligoknotanes has been attempted on chemically bonded Chiralpak AD stationary phases, however met severe difficulties due to their complex isomeric compositions, and in most cases a significant overlap of the isomer fractions was observed. In spite of the limits of presently available chiral stationary phases that allowed only partial resolution of the synthesized topologies, oligoknotanes have been shown to be of high fundamental interest due to their unprecedented chirality. The chirality descriptions of topologically chiral unsymmetrical dumbbell 4, and the linear tetraknotane 5 are analogous to the Fischer projections of erythrose/threose and hexaric acid, respectively, while the isomeric composition of the branched tetraknotane 8 is completely unique. Moreover, the linear and branched tetraknotanes are constitutional isomers. Chirality of knotanophanes represents, in turn, analogies to known cyclic forms of peptides or sugars with multiple stereogenic centers.

17.
Chemistry ; 10(8): 1878-83, 2004 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-15079826

RESUMO

The growing number of molecular assemblies with unusual geometry and topology requires from time to time a revision of certain aspects of stereochemistry. The present paper analyzes several representatives of intertwined molecules that have bridges connecting their loops. In spite of the experimentally proven chirality, these species lack elements of both classical and topological chirality. Due to the relationship of these types of molecules to the well-recognized topologically nontrivial compounds, such as catenanes and knots, we propose the term "residual topology" illustrated by a simple scheme of excessive or missing bridges that could be excluded or included, respectively, in molecular graphs of these species to render them topologically nontrivial. This concept paper represents, therefore, an update on the currently applied nomenclature.

18.
Org Lett ; 6(7): 1075-8, 2004 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-15040726

RESUMO

A method allowing for an unprecedented controllable functionalization of oligoamines via N,N-bis-sulfonylation with various sulfonyl chlorides has been developed. Depending on the nature of the sufonyl chloride and reaction conditions such as base, time of reaction, and temperature, each amino group can be selectively mono- or bis-sufonylated. The procedure was investigated in detail with the model substance tris(2-aminoethyl)amine and applied for the preparation of dumbbell-shaped coupled dendrons and second-generation sulfonimide-decorated dendrimers.

20.
Chemistry ; 9(15): 3507-17, 2003 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-12898678

RESUMO

The readily available in gram quantities tris(allyloxy)knot of the amide-type 5 (knotane) can be completely and partially deprotected with nBu(3)SnH in the presence of a palladium catalyst resulting in hydroxyknotanes 7-9. These, in turn, react with diethylchlorophosphate giving rise to knotanes equipped with between one and three phosphoryl groups. Sulfonylation of bis(allyloxy)monohydroxyknotane 8 with p-toluenesulfonyl chloride and, following removal of one or two allyl groups from the intermediate monosulfonate 13, give rise to sulfonyloxy-allyloxy-hydroxy- and sulfonyloxy-dihydroxy-knotanes 15 and 14, respectively. This provides a convenient method for the preparation of knotanes with any substitution pattern. All new knotanes have been isolated in preparative amounts and as highly pure substances with an exception of allyloxy-dihydroxyknotane 9. This compound could only be obtained as a mixture with the corresponding monohydroxy-derivative 8. The structures of all synthesized compounds were established by means of FAB and MALDI TOF mass spectrometry, (1)H and (31)P NMR spectroscopy. The triphosphorylated knotane 10 exhibits high solubility in alcohols, allowing its complete enantiomeric resolution with a commercially available chiral HPLC column. (1)H,(1)H DQF-COSY correlation spectroscopy along with H/D exchange experiments and ab initio calculations provided the first detailed (1)H NMR signal assignments of knotanes in [D(6)]DMSO solution. The combination of variable temperature (1)H and (31)P NMR spectroscopy and molecular modeling has been applied to study the conformational behavior of the new knotanes in different solvents. It has been shown that in DMSO solution at room temperature knotanes exist in a relatively rigid nonsymmetrical conformation similar to that found in the solid state while faster conformational exchange leading to the average D(3) symmetrical structure was detected in a number of other solvents.


Assuntos
Amidas/química , Dicroísmo Circular , Espectroscopia de Ressonância Magnética/métodos , Modelos Moleculares , Conformação Molecular , Solventes/química , Espectrometria de Massas de Bombardeamento Rápido de Átomos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Estereoisomerismo
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