First total synthesis of asperilactone B. Revision of absolute stereochemistry of asperilactones B and C.

The first total synthesis and absolute configuration assignment of asperilactone B (I) have been accomplished. Additionally, a revision of the absolute stereochemistry of asperilactone C has been done. The first total synthesis of the opposite enantiomer of asperilactone B (ent-I) has also been achieved, as well as that of C-7 epimers of both asperilactones B (8) and C (9).

Synthesis and biological activity of thiophene bioisosteres of natural styryl lactone goniofufurone and related compounds.

Ten new thiophene derivatives related to goniofufurone have been obtained by multistep synthesis starting from d-glucose. The critical step of the synthesis was the Grignard reaction of 2-thienyl magnesium bromide with a protected dialdose, yielding the C-5 epimeric thiophene derivatives 9 and 10. The mixture was oxidized to the 5-keto derivative 11, which after deprotection was converted to the corresponding keto-lactone 14. Stereoselective reduction of 14 afforded the thiophene mimic of goniofufurone 3. Esterification of 3 with cinnamic or 4-fluorocinnamic acid gave hybrids 5-7. Synthesized analogues were evaluated for their in vitro cytotoxicity against several tumour cell lines. The vast majority of them showed better activity than lead 1. In the culture of K562 cells, compound 3 was more active than the commercial antitumour drug doxorubicin. Structural features of analogues important for their antiproliferative activities were identified by SAR analysis. Pro-apoptotic potential examination of compound 3 on the K562 cell line was performed using flow cytometry, double fluorescence staining and apoptotic morphology screening. Results show that this derivative induces cell membrane disruptions attributable to apoptosis and induces the apoptotic morphology, but decreasing simultaneously the population of cells in the subG1 phase of the cell cycle. The results further suggest that analogue 3 achieves strong cytotoxicity without causing DNA fragmentation. This is clearly indicated by the relatively low incidence of micronuclei, as well as the SAR analysis of all biological effects.

Cu(II) complexes with a salicylaldehyde derivative and α-diimines as co-ligands: synthesis, characterization, biological activity. Experimental and theoretical approach.

Copper(II) complexes with an α-diimine show a wide variety of biological activities, such as antibacterial, antifungal, antioxidant and anticancer. In this work, we synthesized and structurally characterized two novel Cu(II) complexes with methyl 3-formyl-4-hydroxybenzoate (HL) and α-diimines: 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). Crystal structure analysis shows that the formulas of the compounds are [Cu(bipy)(L)(BF4)] (1) and [Cu(phen)(L)(H2O)](BF4)·H2O (2), with BF4- as a ligand in complex 1, which is rarely coordinated to metals. Both complexes have a square pyramidal geometry, while DFT calculations showed that the most stable structures of complexes 1 and 2 in a water/DMSO mixture are square-planar derivatives [Cu(bipy)(L)]+ and [Cu(phen)(L)]+. The antibacterial activity of compounds was evaluated in vitro on four Gram-negative and four Gram-positive bacterial strains. Complex 2 showed greater antibacterial activity towards all bacterial strains comparable to the control compound Amikacin. Complex 2 exerted a strong cytotoxic effect against the tested cancer cell lines (IC50 values ranging from 0.32 to 0.44 µM). Both complexes caused apoptotic cell death in HeLa cells and a noticeable in vitro antiangiogenic effect. In the concentration range of 5 to 100 µM, the complexes showed the absence of a genotoxic effect and displayed a protective effect against oxidative DNA damage induced by H2O2 in human peripheral blood cells. The interaction between the compounds and calf-thymus DNA was evaluated by diverse techniques suggesting a tight binding, which was also confirmed by molecular docking. In addition, it was found that the complexes bind tightly and reversibly to bovine and human serum albumin.

On the Selectivity in the Synthesis of 3-Fluoropiperidines Using BF3-Activated Hypervalent Iodine Reagents.

Fluorinated piperidines find wide applications, most notably in the development of novel therapies and agrochemicals. Cyclization of alkenyl N-tosylamides promoted by BF3-activated aryliodine(III) carboxylates is an attractive strategy to construct 3-fluoropiperidines, but it suffers from selectivity issues arising from competitive oxoaminations and the inability to easily modulate the reactions diastereoselectivity. Herein, we report an itemized optimization of the reaction conditions carried out on both cyclic and acyclic substrates and outline the origins of substrate- and reagent-based stereo-, regio-, and chemoselectivity. Extensive mechanistic studies encompassing multinuclear NMR spectroscopy, deuterium labeling, rearrangements on stereodefined substrates, and careful structural analyses (NMR and X-ray) of the reaction products are performed. This revealed the processes and interactions crucial for achieving controlled preparation of 3-fluoropiperidines using I(III) chemistry and has provided an advanced understanding of the reaction mechanism. In brief, we propose that BF3-coordinated I(III) reagents attack C═C to produce the corresponding iodiranium(III) ion, which then undergoes diastereodetermining 5-exo-cyclization. Transiently formed pyrrolidines with an exocyclic σ-alkyl-I(III) moiety can further undergo aziridinium ion formation or reductive ligand coupling processes, which dictate not only the final product's ring size but also the chemoselectivity. Importantly, the selectivity of the reaction depends on the nature of the ligand bound to I(III) and the presence of electrolytes such as TBABF4. Reported findings will facilitate the usage of ArI(III)-dicarboxylates in the reliable construction of fluorinated azaheterocycles.

Bioisosteric ferrocenyl 1,3-thiazolidine-4-carboxylic acid derivatives: In vitro antiproliferative and antimicrobial evaluations.

To improve the antiproliferative effect of ALC67 (diastereomeric mixture of ethyl 2-phenyl-3-propioloyl-1,3-thiazolidine-4-carboxylate), its structure was modified via (i) bioisosteric substitution of the phenyl ring by the ferrocene unit and (ii) replacing the propiolamide side-chain in ACL67 with other acyl groups having differing electrophilicities. In this way, a small library of methyl N-acyl-2-ferrocenyl-1,3-thiazolidine-4-carboxylates (13 compounds in total) was created and characterized by spectral and crystallographic means. The last N-acylation step was highly diastereoselective toward the cis-diastereomer. In solution, most of the obtained compounds existed as a mixture of two rotamers and displayed a preference for the syn-orientation around the CN bond. A twisted 5T4 envelope conformation was adopted by the derivative containing the N-phenoxyacetyl group in the crystalline state. Two derivatives with chloroacetyl and bromoacetyl groups in the N-3 side chain were cytotoxic to fibroblasts and hepatocellular cancer cells in the low micromolar range (IC50(MRC5) = 9.0 and 11.8 µM, respectively, and IC50(HepG2) = 10.6 and 18.4 µM, respectively) causing an effect similar to the lead compound (IC50(HepG2) = 10.0 µM) and cisplatin (IC50(MRC5) = 4.0 µM and IC50(HepG2) = 7.7 µM). Several derivatives also manifested modest antimicrobial effects against the studied microbial strains (MICs in the range from 0.44 to 4.0 µmol/mL). Our findings demonstrated that the introduction of a ferrocene core facilitated the preparation of optically pure analogs of ALC67 and that the cytotoxicity of compounds may be enhanced by adding proper electrophilic centers to the N-acyl side-chain.

The first total synthesis and revision of absolute stereochemistry of natural cytotoxic lactone cleistanolate.

Development of a synthetic route applicable to d-ribose and d-xylose enabled the synthesis of cleistanolate putative structure, its five stereoisomers, and led to revision and confirmation of absolute stereochemistry of the natural product. Key steps of the synthesis included zinc-mediated THF ring-opening and stereoselective dihydroxylation under the Upjohn conditions. The first total synthesis of cleistanolate was completed in eight steps starting from d-xylose. The C-5 stereocenter of the natural product was assigned the correct (5S)-stereochemistry. Cytotoxicity of natural product was briefly investigated.

Natural product protulactone A: Total synthesis from D-galactose, X-ray analysis and biological evaluation.

Synthesis of protulactone A (PLA, 1) and twelve of its analogues have been achieved starting from d-galactose. PLA was isolated in the crystalline state, and its crystal structure was determined utilizing X-ray crystallography, which confirmed the assumed stereochemistry at all stereocenters. All tested compounds displayed antiproliferative activity against a panel of tumour cell lines, and all of them were non-cytotoxic toward the normal cells (MRC-5). Natural product PLA (1) was the most active against the K562 and MCF-7 cell lines (IC50 6.52 and 2.20 µM, respectively). Some of the synthesized derivatives showed very potent cytotoxicity, especially analogues 11, 13 and 15 (IC50 1.08-1.14 µM against MCF-7), and 9 and 14 (IC50 1.29 and 1.64 µM against K562). SAR analysis indicated important structural motifs for antiproliferative activity. Unfortunately, PLA (1), its C-7 epimer (2) and demethylated analogue (3) did not display a significant antimicrobial activity (two Gram-positive and two Gram-negative bacteria and one fungal strain) and they also cannot affect the ability to modulate bacterial communication.

Design, synthesis, and biological evaluation of thiazole bioisosteres of goniofufurone through in vitro antiproliferative activity and in vivo toxicity.

The synthesis of several new goniofufurone bioisosteres was achieved in which the phenyl residue was replaced by a thiazole ring. The key steps of the synthesis included the initial condensation of cyanohydrin benzoates with cysteine ethyl ester hydrochloride, followed by the subsequent reaction of resulting C-4' epimeric thiazolines with DBU, to introduce 5-deoxy functionality and to elaborate the thiazole ring in one step. Synthesized compounds showed potent growth inhibitory effects against selected human tumour cell lines, especially bioisostere 4, which in the culture of MCF-7 cells displayed the highest activity (IC50 = 0.19 nM) of all compounds under evaluation. This molecule exhibited 64474-fold higher antiproliferative activity than lead 2 and was1053-fold more active than the commercial antitumour agent doxorubicin in the culture of MCF-7 cells. The structural features of the tested compounds responsible for their antiproliferative activity have been identified by preliminary SAR analysis. The toxicity of the most active compound 4 was assessed by an in vivo experiment in a zebrafish model (Danio rerio), whereupon it was found non-toxic at any of the tested concentrations up to 125 µM.

A novel binuclear hydrazone-based Cd(II) complex is a strong pro-apoptotic inducer with significant activity against 2D and 3D pancreatic cancer stem cells.

A novel binuclear Cd complex (1) with hydrazone-based ligand was prepared and characterized by spectroscopy and single crystal X-ray diffraction techniques. Complex 1 reveals a strong pro-apoptotic activity in both human, mammary adenocarcinoma cells (MCF-7) and pancreatic AsPC-1 cancer stem cells (CSCs). While apoptosis undergoes mostly caspase-independent, 1 stimulates the activation of intrinsic pathway with noteworthy down regulation of caspase-8 activity in respect to non-treated controls. Distribution of cells over mitotic division indicates that 1 caused DNA damage in both cell lines, which is confirmed in DNA interaction studies. Compared to 1, cisplatin (CDDP) does not achieve cell death in 2D cultured AsPC-1 cells, while induces different pattern of cell cycle changes and caspase activation in 2D cultured MCF-7 cells, implying that these two compounds do not share similar mechanism of action. Additionally, 1 acts as a powerful inducer of mitochondrial superoxide production with dissipated trans-membrane potential in the majority of the treated cells already after 6 h of incubation. On 3D tumors, 1 displays a superior activity against CSC model, and at 100 µM induces disintegration of spheroids within 2 days of incubation. Fluorescence spectroscopy, along with molecular docking show that compound 1 binds to the minor groove of DNA. Compound 1 binds to the human serum albumin (HSA) showing that the HSA can effectively transport and store 1 in the human body. Thus, our current study strongly supports further investigations on antitumor activity of 1 as a drug candidate for the treatment of highly resistant pancreatic cancer.

Novel O-methyl goniofufurone and 7-epi-goniofufurone derivatives: synthesis, in vitro cytotoxicity and SAR analysis.

Novel goniofufurone (1) and 7-epi-goniofufurone (2) derivatives bearing a methoxy group at the C-5 and/or C-7 positions were prepared and their in vitro antitumour activity against some human tumour cell lines was evaluated. Some of the analogues displayed powerful antiproliferative effects against the studied tumour cells, but almost all of them were non-cytotoxic toward the normal cells (MRC-5). A SAR study reveals that the introduction of a methoxy group at the C-7 position may increase the antiproliferative effects of the analogues. The most active compounds are 7-O-methyl derivatives of goniofufurone (3) and 7-epi-(+)-goniofufurone (6), which exhibited 1177- and 451-fold higher potencies than the leads 1 and 2 toward the MDA-MB 231 cell line. At the same time, compound 3 is almost 1.5-fold more active than the commercial drug doxorubicin (DOX) against the same cell line. Flow cytometry data confirmed that the cytotoxic effects of these analogues are mediated by apoptosis, additionally revealing that these molecules induced changes in the K562 cell cycle distribution.

Anticancer potential of new steroidal thiazolidin-4-one derivatives. Mechanisms of cytotoxic action and effects on angiogenesis in vitro.

The synthesis and cytotoxic activities determination of new steroidal mono- and bis(thiazolidin-4-ones) 4a-f and 5a-f have been performed. Their anticancer action was also evaluated in comparison to previously synthesized and reported corresponding steroidal thiosemicarbazones. All compounds were obtained as stereoisomeric mixtures with different configuration (E or Z) in the hydrazone moiety at the C-3 position. After several consecutive crystallizations diastereomerically pure major (E)-isomers of mono-thiazolidin-4-ones were isolated. The structure and stereochemistry of 2,4-thiazolidinedione,2-[(17-oxoandrost-4-en-3-ylidene)hydrazone] were confirmed by X-ray analysis. A pathway for the formation of thiazolidin-4-one ring was proposed. The steroid thiazolidinone derivatives examined in this study exerted selective concentration-dependent cytotoxic activities on six tested malignant cell lines. Ten out of twelve examined compounds exhibited strong cytotoxic effects on K562 cells (IC50 values from 8.5µM to 14.9µM), eight on HeLa cells (IC50 values ranging from 8.9µM to 15.1µM) while against MDA-MB-361 cells six compouds exerted similar or even higher cytotoxic action (IC50 values from 12.7µM to 25.6µM) than cisplatin (21.5µM) which served as a positive control. Eight of these ten compounds showed high selectivity in the cytotoxic action against HeLa and K562 cancer cell lines when compared with normal human fibroblasts MRC-5 and normal human PBMC. The study of mechanisms of the anticancer activity of the two selected compounds, mono- and bis(thiazolidin-4-one) derivatives of 19-norandrost-4-ene-3,17-dione 4a and 5a, revealed that both of these compounds induced apoptosis in HeLa cells through extrinsic and intrinsic signalling pathways. Treatment of EA.hy926 cells with sub-toxic concentrations of these compounds led to the inhibition of cell connecting and sprouting, and tube formation. The synthesized compounds exhibited poor antioxidant activity.

Design, synthesis and in vitro antitumour activity of new goniofufurone and 7-epi-goniofufurone mimics with halogen or azido groups at the C-7 position.

A series of new antitumour lactones containing the [3.3.0] bicyclic furano-lactone core and the halogen or azido group at the C-7 position have been designed, synthesized, and evaluated for their in vitro antitumour activity against a panel of human tumour cell lines. Some of the analogues displayed powerful antiproliferative effects to certain human tumour cells, but all of them were devoid of any cytotoxicity towards the normal foetal lung fibroblasts (MRC-5). A SAR study reveals the structural features of these lactones that may affect their antiproliferative activity. These are: the nature of substituent present at the C-7 position, stereochemistry at the C-7 position, the absence of phenyl group at the C-7 position. Flow cytometry data indicate that the cytotoxic effects of the synthesized analogues in a culture of K562 cells are mediated by apoptosis, additionally revealing that these molecules induced changes in cell cycle distribution of these cells. Results of Western blot analysis suggested that the most of synthesized compounds induce apoptosis in K562 cells in caspase-dependent way.

Mannich bases of 1,2,4-triazole-3-thione containing adamantane moiety: Synthesis, preliminary anticancer evaluation, and molecular modeling studies.

A series of 18 novel N-Mannich bases derived from 5-adamantyl-1,2,4-triazole-3-thione was synthesized and characterized using NMR spectroscopy and X-ray diffraction technique. All derivatives were evaluated for their anticancer potential against four human cancer cell lines. Several tested compounds exerted good cytotoxic activities on K562 and HL-60 cell lines, along with pronounced selectivity, showing lower cytotoxicity against normal fibroblasts MRC-5 compared to cancer cells. The effects of compounds 5b, 5e, and 5j on the cell cycle were investigated by flow cytometric analysis. It was found that these compounds cause the accumulation of cells in the subG1 and G1 phases of the cell cycle and induce caspase-dependent apoptosis, while the anti-angiogenic effects of 5b, 5e, and 5j have been confirmed in EA.hy926 cells using a tube formation assay. Further, the interaction of Bax protein with compound 5b was investigated by means of molecular modeling, applying the combined molecular docking/molecular dynamics approach.

Synthesis, characterization, cytotoxicity and antiangiogenic activity of copper(II) complexes with 1-adamantoyl hydrazone bearing pyridine rings.

Three novel copper complexes with tridentate N2O ligand di(2-pyridil) ketone 1-adamantoyl hydrazone (Addpy) of the formula [Cu(II)2Cu(I)2(Addpy)2Br2(µ-Br4)] (1), catena-poly[CuCl(µ-Addpy)(µ-Cl)CuCl2]n (2) and [Cu(Addpy)(NCS)2] (3) were synthesized. Complexes are characterized by X-ray crystallography, spectral (UV-Vis, FTIR), electrochemical (CV) analyses, and magnetochemical measurements. Investigation of anticancer potential of Cu(II) complexes, mode of cell death, apoptosis, and inhibition of angiogenesis were performed. All tested malignant cell lines (HeLa, LS174, A549, K562, and MDA-MB-231) showed high sensitivity to the examined Cu(II) complexes. It has been shown that the complexes induce apoptosis in the caspase 3-dependent manner, whereas the anti-angiogenic effects of 1, 2, and 3 have been confirmed in EA.hy926 cells using a tube formation assay.

Synthesis and antiproliferative activity of goniobutenolides A and B, 5-halogenated crassalactone D derivatives and the corresponding 7-epimers.

A new synthesis of goniobutenolides A (1) and B (2) and the corresponding 7-epimers has been achieved starting from diacetone d-glucose. The key step of the synthesis is a new one-pot sequence that commenced with Z-selective Wittig (or Horner-Wadsworth-Emmons) olefination, followed by successive γ-lactonisation and ß-elimination. The above-mentioned unsaturated lactones were then converted to the corresponding 5-halogenated crassalactone D derivatives by using the appropriate haloetherification protocol. The most of synthesized compounds exhibited potent cytotoxic activities against a panel of tumour cell lines. The main structural features responsible for their antitumour potency have been revealed by means of SAR analysis. Flow cytometry data suggested that cytotoxic effects of these compounds in the culture of K562 cells might be mediated by apoptosis, additionally revealing that these molecules induced changes in cell cycle distribution of these cells. Results of semi-quantitative Western blot analysis indicate that the most of synthesized compounds induce apoptosis in a caspase-dependent manner.

Mixed-ligand MnII and CuII complexes with alternating 2,2'-bipyrimidine and terephthalate bridges.

The novel polymeric complexes catena-poly[[diaquamanganese(II)]-µ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')-[diaquamanganese(II)]-bis(µ-terephthalato-κ(2)O(1):O(4))], [Mn2(C8H4O4)2(C8H6N4)(H2O)4]n, (I), and catena-poly[[[aquacopper(II)]-µ-aqua-µ-hydroxido-µ-terephthalato-κ(2)O(1):O(1')-copper(II)-µ-aqua-µ-hydroxido-µ-terephthalato-κ(2)O(1):O(1')-[aquacopper(II)]-µ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')] tetrahydrate], {[Cu3(C8H4O4)2(OH)2(C8H6N4)(H2O)4]·4H2O}n, (II), containing bridging 2,2'-bipyrimidine (bpym) ligands coordinated as bis-chelates, have been prepared via a ligand-exchange reaction. In both cases, quite unusual coordination modes of the terephthalate (tpht(2-)) anions were found. In (I), two tpht(2-) anions acting as bis-monodentate ligands bridge the Mn(II) centres in a parallel fashion. In (II), the tpht(2-) anions act as endo-bridges and connect two Cu(II) centres in combination with additional aqua and hydroxide bridges. In this way, the binuclear [Mn2(tpht)2(bpym)(H2O)4] entity in (I) and the trinuclear [Cu3(tpht)2(OH)2(bpym)(H2O)4]·4H2O coordination entity in (II) build up one-dimensional polymeric chains along the b axis. In (I), the Mn(II) cation lies on a twofold axis, whereas the four central C atoms of the bpym ligand are located on a mirror plane. In (II), the central Cu(II) cation is also on a special position (site symmetry -1). In the crystal structures, the packing of the chains is further strengthened by a system of hydrogen bonds [in both (I) and (II)] and weak face-to-face π-π interactions [in (I)], forming three-dimensional metal-organic frameworks. The Mn(II) cation in (I) has a trigonally deformed octahedral geometry, whereas the Cu(II) cations in (II) are in distorted octahedral environments. The Cu(II) polyhedra are inclined relative to each other and share common edges.

(E)-4-[(2-carbamoylhydrazinylidene)methyl]-3-hydroxy-5-hydroxymethyl-2-methylpyridin-1-ium nitrate.

The title compound, C9H13N4O3(+)·NO3(-), is the first structurally characterized Schiff base derived from semicarbazide and pyridoxal. Unusually for an unsubstituted semicarbazone, the compound adopts a syn conformation, in which the carbonyl O atom is in a cis disposition relative to the azomethine N atom. This arrangement is supported by a pair of hydrogen bonds between the organic cation and the nitrate anion. The cation is essentially planar, with only a hydroxymethyl O atom deviating significantly from the mean plane of the remaining atoms (r.m.s. deviation of the remaining non-H atoms = 0.01 Å). The molecules are linked into flat layers by N-H···O and C-H···O hydrogen bonds. O-H···O hydrogen bonds involving the hydroxymethyl group as a donor interconnect the layers into a three-dimensional structure.

4-Di-chloro-methyl-4-methyl-5-(nitro-meth-yl)cyclo-hex-2-enone.

In the title compound, C9H11Cl2NO3, the six-membered ring adopts a screw-chair conformation. In the crystal, two different C-H⋯O hydrogen bonds involving the same acceptor atom connect the mol-ecules into a chain extending along the c-axis direction.