Synthesis and Anticancer Activity of Phosphinoylated and Phosphonoylated N-Heterocycles Obtained by the Microwave-Assisted Palladium Acetate-Catalyzed Hirao Reaction.

A literature survey showed that different derivatives with the 9-phenyl-9H-carbazole or the dihydroindoline scaffold may be of biological activity including cytotoxic effect. Driven by this experience, P-functionalized derivatives of these N-heterocycles were synthesized. Three N-heterocycles, 9-(4-bromophenyl)-9H-carbazole, 3-bromo-9-phenyl-9H-carbazole and 1-(5-bromoindolin-1-yl)ethan-1-one, were coupled with dialkyl phosphites and diarylphosphine oxides using Pd(OAc)2 (10 %) as the catalyst precursor and triethylamine as the base in ethanol under microwave irradiation. The excess of the Y2 P(O)H reagent (Y=alkoxy, aryl) (30 %) served as the P-ligand in its trivalent tautomeric form (Y2 POH), hence there was no need for the usual P-ligands meaning cost and environmental burden. Hence, the presented method is a "green" approach that proved to be more efficient than the preparation by the traditional method. The products, dialkyl phosphonates and tertiary phosphine oxides obtained in 58-84 % yields were characterized, one of them also by single crystal X-ray analysis, and were subjected to in vitro biological activity evaluation. A (carbazol)yl-phenylphosphonate, an N-phenyl-(carbazol)yl-phosphonate, a (carbazol)yl-phenylphosphine oxide and an N-phenyl-(carbazol)ylphosphine oxide revealed a significant cytotoxic activity on A549 human non-small-cell lung carcinoma and MonoMac-6 acute monocytic leukemia cancer cells. The cytotoxic effect was significant as compared to that of the reference compounds.

A Study of the Bisphosphonic Derivatives from the Pudovik Reaction of Dialkyl α-Oxophosphonates and >P(O)H Reagents: X-ray Structure and Bioactivity.

New hydroxy-methylenebisphosphonic derivatives were prepared with different P-functions. The outcome of the reaction of α-oxophosphonates (YC(O)P(O)(OR)2) and dialkyl phosphites or diarylphosphine oxides depended on the Y substituent of the oxo-compound, the nature of the P-reagent and the amount of the diethylamine catalyst. Starting from dimethyl α-oxoethylphosphonate, in the presence of 5% of diethylamine, the corresponding Pudovik adduct was the single product. While using 40% of the catalyst, the rearranged species with the >P(O)-O-CH-P(O)< skeleton was the exclusive component. A similar reaction of α-oxobenzylphosphonate followed the rearrangement protocol. X-ray crystallography revealed not only the spatial structures of the three products, but also an intricate pattern evolving from the interplay of slight chemical differences, solvent inclusion and disorder as well as H-bridge patterns, which invite further investigation. In vitro activity of the compounds was assessed on different tumor cell cultures using end-point-type cell tetrazolium-based measurements. These structure-activity studies revealed a cytostatic effect for four rearranged derivatives containing aromatic units. One of them had a pronounced effect on MDA-MB 231 and Ebc-1 cells, showing IC50 = 37.8 and 25.9 µM, respectively.

The resolution of acyclic P-stereogenic phosphine oxides via the formation of diastereomeric complexes: A case study on ethyl-(2-methylphenyl)-phenylphosphine oxide.

As an example of acyclic P-chiral phosphine oxides, the resolution of ethyl-(2-methylphenyl)-phenylphosphine oxide was elaborated with TADDOL derivatives, or with calcium salts of the tartaric acid derivatives. Besides the study on the resolving agents, several purification methods were developed in order to prepare enantiopure ethyl-(2-methylphenyl)-phenylphosphine oxide. It was found that the title phosphine oxide is a racemic crystal-forming compound, and the recrystallization of the enantiomeric mixtures could be used for the preparation of pure enantiomers. According to our best method, the (R)-ethyl-(2-methylphenyl)-phenylphosphine oxide could be obtained with an enantiomeric excess of 99% and in a yield of 47%. Complete racemization of the enantiomerically enriched phosphine oxide could be accomplished via the formation of a chlorophosphonium salt. Characterization of the crystal structures of the enantiopure phosphine oxide was complemented with that of the diastereomeric intermediate. X-ray analysis revealed the main nonbonding interactions responsible for enantiomeric recognition.

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction.

A family of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides was synthesized by the microwave-assisted solvent-free addition of dialkyl phosphites and diphenylphosphine oxide, respectively, to imines formed from benzaldehyde derivatives and primary amines. After optimization, the reactivity was mapped, and the fine mechanism was evaluated by DFT calculations. Two α-aminophosphonates were subjected to an X-ray study revealing a racemic dimer formation made through a N-H···O=P intermolecular hydrogen bridges pair.

Resolution of 1-n-butyl-3-methyl-3-phospholene 1-oxide with TADDOL derivatives and calcium salts of O,O'-Dibenzoyl-(2R,3R)- or O,O'-di-p-toluoyl-(2R,3R)-tartaric acid.

The resolution methods applying (-)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane ("TADDOL"), (-)-(2R,3R)-α,α,α',α'-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol ("spiro-TADDOL"), as well as the acidic and neutral Ca(2+) salts of (-)-O,O'-dibenzoyl- and (-)-O,O'-di-p-toluoyl-(2R,3R)-tartaric acid were extended for the preparation of 1-n-butyl-3-methyl-3-phospholene 1-oxide in optically active form. In one case, the intermediate diastereomeric complex could be identified by single-crystal X-ray analysis. The absolute P-configuration of the enantiomers of the phospholene oxide was also determined by comparing the experimentally obtained and calculated CD spectra.

Synthesis of atropisomeric 1-phenylpyrrole-derived amino alcohols: new chiral ligands.

An efficient synthetic method has been developed for the preparation of a new family of atropisomeric amino alcohols with 1-phenylpyrrole backbone. The synthesis is based on the different reactivities of the two carboxylic groups in optically active 1-[2-carboxy-6-(trifluoromethyl)phenyl]-1H-pyrrole-2-carboxylic acid (1). The chemical structures of the key intermediates were confirmed by spectroscopic methods and single crystal X-ray diffraction measurements. The very first application of a new optically active amino alcohol as catalyst for the enantioselective addition of diethylzinc to benzaldehyde demonstrated the practical usefulness of atropisomeric compounds in which there are six-atom chains between the two functional groups.

On the symmetry of wulfenite (Pb[MoO4]) from Meǽica (Slovenia).

Wulfenite [lead(II) molybdate(VI)] is known as a scheelite structure in the I4(1)/a space group. The structure of the unusual `hemimorphic' wulfenite crystals from the Meǽica mine was refined in the noncentrosymmetric space group I ̅4 using a Pb/Mo exchange disorder model with the approximate composition Pb(0.94)Mo(0.06)[MoO(4)]. Pb atoms in the 2b positions are substituted by Mo at about 12%. The crystal is shown to be twinned by inversion. Hemimorphism may result from the short-range chemical ordering of the metal atoms at the 2b positions.

Dichloridobis(2-methoxy-dibenzo[c,e][1,2]oxaphospho-rine-κP)platinum(II) trichloro-methane solvate.

The title compound, [PtCl(2)(C(13)H(11)O(2)P)(2)]·CHCl(3), has a rare PtCl(2) bridging of two dibenzooxaphospho-rine ligands through the metal atom. The Pt(II) ion is in a slightly distorted square-planar environment. The trichloro-methane solvent mol-ecule shows rotational disorder (major occupancy is 0.75) and is placed near to the inversion centre at (1/2, 1/2, 0) in channels parallel to the a axis. The solvent mol-ecule is linked to the complex mol-ecule via inter-molecular bifurcated C-H⋯Cl and C-H⋯O hydrogen bonds. The crystal structure is further stabilized by π-π inter-actions involving the benzene rings, with a centroid-centroid distance of 3.658 (8) Å.

The typical crystal structures of a few representative α-aryl-α-hydroxyphosphonates.

The crystal structures of seven α-aryl-α-hydroxyphosphonates synthesized by the Pudovik reaction of substituted benzaldehydes and dialkyl phosphites, namely dimethyl [(hydroxy)(phenyl)methyl]phosphonate, C9H13O4P, dimethyl [(3,4-dimethoxyphenyl)(hydroxy)methyl]phosphonate, C11H17O6P, dimethyl (1-hydroxy-1-phenylethyl)phosphonate, C10H15O4P, dimethyl [1-hydroxy-1-(4-nitrophenyl)ethyl]phosphonate, C10H14NO6P, dibenzyl [hydroxy(2-nitrophenyl)methyl]phosphonate, C21H20NO6P, dibenzyl [(3-chlorophenyl)(hydroxy)methyl]phosphonate, C21H20ClO4P, and dibenzyl [hydroxy(4-methylphenyl)methyl]phosphonate, C22H23O4P, were studied to gain a better understanding of the organization in this type of molecule in the solid state. The crystals obtained for this series of compounds show a balance between C-OH...O=P chain-linked packing and the dimeric types of hydrogen-bond bridges of intermolecular pairs of such functions. The description is based on primary graph-set descriptors. Using graph-set descriptors one level deeper (i.e. secondary graph sets of the C-H...O type) revealed a similarity in the graph-set descriptors, suggesting a fine interplay of substituent- and shape-dependent effects on strong-weak interactions. It seems that the formation of chains or dimers is governed not only by the presence of a tertiary Cα atom, but also by the nature and crowding of the ortho substituents of the α-aryl group.

Chemical and biological investigation of N-hydroxy-valdecoxib: An active metabolite of valdecoxib.

The inhibition of cyclooxygenase enzymes plays an important role in the treatment of inflammatory diseases. N-Hydroxy-4-(5-methyl-3-phenylisoxazol-4-yl)benzenesulfonamide (3)-a primary metabolite of the highly selective COX-2 inhibitor valdecoxib-was synthesized and stabilized as its monohydrate (3a.H(2)O). The anti-inflammatory properties of 3a.H(2)O were investigated in carrageenan-induced edema and in acute and chronic pain models. Based on our biological investigation, we conclude that N-hydroxy-valdecoxib 3a is an active metabolite of valdecoxib.

New steroid-fused P-heterocycles. Part I. Synthesis and conformational study of dioxaphosphorino[16,17-d]estrone derivatives.

D-ring-fused dioxaphosphorinanes (4-6) in the estrone series were synthetized as epimeric pairs and investigated by NMR and computational methods in order to determine their stereostructures and predominant conformations. The study was performed to evaluate the influence of the rigid sterane framework on the geometry of the condensed hetero ring, with regard to the possible steric effect of the angular methyl group at position 13. Additionally, the steric and electronic effects of the P-substituents on the conformational equilibrium were examined. The distorted-boat conformation of the hetero ring of dioxaphosphorinoestrone 3-methyl ether 4a was confirmed by single-crystal X-ray analysis. This is in good agreement with the observation in solution that, in the case of the boat conformation, the anisotropic shielding effect of the phenyl group of cyclic phosphonate 4a generates an upfield shift for 17-H, as compared with the corresponding chemical shift for epimer 4b. A similar boat conformation was substantiated for derivatives 4b, 5a, 5b and 6b on the basis of the J(H, H) and J(H, P) coupling constants and also ab initio calculations, regardless of the P-configuration. At the same time, the hetero ring of 6a seems to tilt towards a chair-like conformation due to the strong equatorial preference of the N-bis(2-chloroethyl) group.

Resolution of P-stereogenic P-heterocycles via the formation of diastereomeric molecular and coordination complexes (a review).

TADDOL derivatives and the Ca(2+)-salts of tartaric acid derivatives were found to be versatile and generally applicable resolving agents for the preparation of the enantiomers of P-stereogenic heterocyclic phosphine oxides and phosphinates via the formation of the corresponding diastereomeric molecular and coordination complexes. A few of the diastereomeric intermediates were characterized by single crystal X-ray crystallography to gain insights into the binding mode of the corresponding heterocyclic phosphine oxide ("guest") and the resolving agent ("host") and to study the underlying phenomenon of enantiomeric recognition.

Synthesis of novel 17-(5'-iodo)triazolyl-3-methoxyestrane epimers via Cu(I)-catalyzed azide-alkyne cycloadditon, and an evaluation of their cytotoxic activity in vitro.

The regioselective Cu(I)-catalyzed 1,3-dipolar cycloaddition of 3-methoxyestrane 17α- and 17ß-azide epimers (3 and 5) with different terminal alkynes afforded novel 1,4-substituted triazolyl derivatives (8a-f and 11a-f). If the Ph3P in the classical CuAAC process was replaced by Et3N, the formation of small quantities of 5-iodotriazoles (9a-f and 11a-f) was observed. For the preparation of 5-iodo-1,2,3-triazoles (9a-f and 11a-f), an improved method was developed, directly from steroidal azides and terminal alkynes, in reactions mediated by CuI and ICl as iodinating agents. The antiproliferative activities of the structurally related triazoles were determined in vitro with the microculture tetrazolium assay on six malignant human cell lines of gynecological origin (HeLa, A2780, MCF7, MDA-MB-231, MDA-MB-361 and T47D). X-ray analysis revealed the presence of the iodo substituent on the 1,2,3-triazole ring.

Sodium halide complexes of ribose derivatives and their unusual crystal structures.

Crystalline complexes of D-ribose, D-ribono-1,4-lactone and methyl ß-D-ribopyranoside with sodium halides were synthesized and some of their crystal structures determined. Crystal structures of two lactone complexes and a methyl ß-D-ribopyranoside reveal the mode of the salt binding and the intricate interplay of cation coordination and hydrogen bonding in these complexes. When complexed with NaBr, the ribopyranoside is in the (1)C(4) shape whereas ribose with no salt present has the (4)C(1) shape. It is also demonstrated that such complexes can be easily prepared in solid state reaction using a ball mill.

Preparation of 2-amino-2-C-glycosyl-acetonitriles from C-glycosyl aldehydes by Strecker reaction.

Synthesis of new 2-amino-2-C-D-glycosyl-acetonitriles in a Strecker reaction from various C-glycosyl aldehydes, chiral amines, and HCN was carried out. While aminonitriles from glycal and 2-deoxy-ß-D-glycosyl aldehydes were prepared in satisfactory yields, lower yields were obtained with C-glycosyl aldehydes. Strecker reaction with the benzyl-protected 1-C-formyl-D-galactal and S- or R-1-phenylethylamine (S-PEA or R-PEA) yielded predominantly the R-configured C-glycosyl aminoacetonitrile. The direction of the nucleophilic addition appears to be governed by the configuration of the anomeric carbon with ß-linked sugars. Since the stereochemistry of the transition state is unknown according to the configuration of the major product a Felkin-Ahn selectivity can be mainly presumed.

Double diastereocontrol in bifunctional thiourea organocatalysis: iterative Michael-Michael-Henry sequence regulated by the configuration of chiral catalysts.

The importance and reactivity consequences of the double diastereocontrol in noncovalent bifunctional organocatalysis were studied. The results suggest that the bifunctional thioureas can have synthetic limitations in multicomponent domino or autotandem catalysis. Nevertheless, we provided a means to exploit this behavior and used the configuration of the chiral catalyst as a control element in organo-sequential reactions.

Charge flipping at work: a case of pseudosymmetry.

Charge flipping (CF) is an amazingly simple structure solution method that uses single-crystal X-ray diffraction data. It is truly ab initio, no preliminary information on atom types, chemical composition, or space group symmetry is required. The algorithm is iterative and alternates between real and reciprocal spaces. Its simplest version only changes (flips) the sign of the electron density below a threshold, while in reciprocal space, it prescribes the moduli of observed structure factors. In this communication, we apply the algorithm in practice. The selected example presents a whole range of difficulties: it is large, contains only light atoms, is noncentrosymmetric, and shows a particularly awkward pseudosymmetry. To solve it with any of the traditional methods requires many hours of computer time, followed by a day of expert's handwork to find missing and to remove spurious atoms. In contrast, the CF algorithm provides the complete structure in a few seconds and without human intervention. It is also remarkable that the success rate is 100%, that is, any starting point in the high-dimensional phase space leads to the solution. The treatment of translational pseudosymmetry is obviously a favorable case. Similar resistant structures with pseudosymmetries or ambiguous space groups are the practical applications where the CF method could well complement standard software procedures.

A new cryptophane receptor featuring three endo-carboxylic acid groups: synthesis, host behavior and structural study.

Examples of a new type of cryptophane molecule incorporating aromatic groups in the bridges (1-4) and, for the first time, being also supplied with three endo-positional ionizable carboxylic acid functions (1) have been synthesized and characterized. The cryptophane triester 2 yielded a solvate (channel inclusion compound) with trichloromethane and water, the X-ray crystal structure of which is reported. The complexation of 1 with low-molecular-weight alcohols in solution was studied, and the liquid-liquid extraction of different metal ions including alkali (Na(+), Cs(+)), alkaline earth (Mg(2+), Ca(2+), Sr(2+), Ba(2+)), and the lanthanide metal ions Eu(3+) and Yb(3+) in an extraction system containing metal nitrate buffer/H(2)O/1/CHCl(3) was examined. Molecular modeling calculations of the cryptophanes 1 and 2, and of the Eu(3+) complex of 1 were carried out contributing to the discussion.

Supramolecular [6]chochin and "Big Mac" made from chiral Piedfort assemblies.

Facile chemical synthesis of the natural chiral-pool-derived host 1 and its subsequent crystallization ("supramolecular synthesis") from different solvents yielded crystalline assemblies. Crystal structure determinations of five of the so formed solvent-inclusion compounds (1 a-1 e) reveal hexagonal symmetries in four cases. The structural characteristics of these chiral host-guest ensembles with varying stoichiometries can be best described as assemblies formed through intra-pair hydrogen bridges of host molecules into Piedfort pairs of differing complexity. Hitherto undescribed, these Piedfort pairs also form even larger regular assemblies that we designate "Big Mac"-like shapes. In the only nonhexagonal case, six independent host molecules form a huge supramolecular analogue of [6]benzocyclophane, also known as [6]chochin, extending this giant supermolecule through intermolecular hydrogen bonds into macroscopic (mm-size) dimensions. As all these crystals are inherently chiral, and new model systems for solid-state applications can be envisaged.