Synthesis of 2-Amino-N'-aroyl(het)arylhydrazides, DNA Photocleavage, Molecular Docking and Cytotoxicity Studies against Melanoma CarB Cell Lines.

Diacylhydrazine bridged anthranilic acids with aryl and heteroaryl domains have been synthesized as the open flexible scaffold of arylamide quinazolinones in order to investigate flexibility versus rigidity towards DNA photocleavage and sensitivity. Most of the compounds have been synthesized via the in situ formation of their anthraniloyl chloride and subsequent reaction with the desired hydrazide and were obtained as precipitates, in moderate yields. All compounds showed high UV-A light absorption and are eligible for DNA photocleavage studies under this "harmless" irradiation. Despite their reduced UV-B light absorption, a first screening indicated the necessity of a halogen at the p-position in relation to the amine group and the lack of an electron-withdrawing group on the aryl group. These characteristics, in general, remained under UV-A light, rendering these compounds as a novel class of UV-A-triggered DNA photocleavers. The best photocleaver, the compound 9, was active at concentrations as low as 2 µΜ. The 5-Nitro-anthranilic derivatives were inactive, giving the opposite results to their related rigid quinazolinones. Molecular docking studies with DNA showed possible interaction sites, whereas cytotoxicity experiments indicated the iodo derivative 17 as a potent cytotoxic agent and the compound 9 as a slight phototoxic compound.

A Convenient Synthesis of Novel Isoxazolidine and Isoxazole Isoquinolinones Fused Hybrids.

Isoxazolidine, isoxazole, and isoquinolinone rings are present in the structure of several natural products and/or pharmaceutically interesting compounds. In this work, facile and efficient pathways have been developed for the preparation of fused frameworks bearing those heterocycles. The successful approaches for both isoxazolidine/isoquinolinone and isoxazole/isoquinolinone hybrid syntheses relied initially on 1,3-dipolar cycloadditions of nitrones and nitrile oxides to indenone and 2-propargylbenzamide, respectively. The construction of the isoquinolinone lactam system followed by performing a selective Schmidt reaction for isoxazolidine derivatives (two steps overall), whereas the isoxazole lactams were reached via an Ullmann-type cyclisation (three steps overall). Key observations were made regarding the stereo- and regioselectivities of the reactions employed, and small libraries of the targeted hybrids were prepared, demonstrating the general applicability of these strategies.

Enantiospecific Total Synthesis and Absolute Configuration Assignment of Chabrolobenzoquinone H.

Chabrolobenzoquinone H (1), a meroditerpene metabolite with cytotoxic activity, is synthesized via a stereoselective Julia-Kocienski olefination between a chiral pool derived aliphatic PT-sulfone and a benzoquinone aldehyde partner. The latter was obtained via consecutive chain extension steps involving a Stille coupling and a stereospecific olefin cross-metathesis reaction followed by malonic ester synthesis and a Krapcho decarboxylation. Furthermore, this total synthesis securely determined the absolute configuration of the targeted natural product.

Total Synthesis of Enantiopure Chabrolonaphthoquinone B Via a Stereoselective Julia-Kocienski Olefination.

The total synthesis of cytotoxic meroditerpenoid naphthoquinone derivative chabrolonaphthoquinone B (1) in an enantiospecific manner is divulged using a chiral pool approach. The key step of our synthetic route is a modified Julia olefination between a sulfone-bearing aliphatic fragment and a Diels-Alder-derived aromatic aldehyde, leading to the stereoselective construction of the E-trisubstituted double bond.

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies.

A number of p-pyridinyl oxime carbamate derivatives were prepared upon the reaction of the corresponding oximes with isocyanates. These novel compounds reacted photochemically in the presence of supercoiled plasmid DNA. Structure-activity relationship (SAR) studies revealed that the substituent on the imine group was not affecting the extend of the DNA damage, whereas the substituent of the carbamate group was critical, with the halogenated derivatives to be able to cause extensive single and double stranded DNA cleavages, acting as "synthetic nucleases", independently of oxygen and pH. Calf thymus-DNA affinity studies showed a good-to-excellent affinity of selected both active and non-active derivatives. Preliminary theoretical studies were performed, in an effort to explain the reasons why some derivatives cause photocleavage and some others not, which were experimentally verified using triplet state activators and quenchers. These theoretical studies seem to allow the prediction of the activity of derivatives able to pass intersystem crossing to their triplet energy state and thus create radicals able to damage DNA. With this study, it is shown that oxime carbamate derivatives have the potential to act as novel effective photobase generating DNA-photocleavers, and are proposed as new leads for "on demand" biotechnological applications in drug discovery and medicine.

Synthesis of inositol phosphate-based competitive antagonists of inositol 1,4,5-trisphosphate receptors.

Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca(2+) channels that are widely expressed in animal cells, where they mediate the release of Ca(2+) from intracellular stores evoked by extracellular stimuli. A diverse array of synthetic agonists of IP3Rs has defined structure-activity relationships, but existing antagonists have severe limitations. We combined analyses of Ca(2+) release with equilibrium competition binding to IP3R to show that (1,3,4,6)IP4 is a full agonist of IP3R1 with lower affinity than (1,4,5)IP3. Systematic manipulation of this meso-compound via a versatile synthetic scheme provided a family of dimeric analogs of 2-O-butyryl-(1,3,4,6)IP4 and (1,3,4,5,6)IP5 that compete with (1,4,5)IP3 for binding to IP3R without evoking Ca(2+) release. These novel analogs are the first inositol phosphate-based competitive antagonists of IP3Rs with affinities comparable to that of the only commonly used competitive antagonist, heparin, the utility of which is limited by off-target effects.

Pyridine and p-Nitrophenyl Oxime Esters with Possible Photochemotherapeutic Activity: Synthesis, DNA Photocleavage and DNA Binding Studies.

Compared to standard treatments for various diseases, photochemotherapy and photo-dynamic therapy are less invasive approaches, in which DNA photocleavers represent promising tools for novel "on demand" chemotherapeutics. A series of p-nitrobenzoyl and p-pyridoyl ester conjugated aldoximes, amidoximes and ethanone oximes were subjected to UV irradiation at 312 nm with supercoiled circular plasmid DNA. The compounds which possessed appropriate properties were additionally subjected to UVA irradiation at 365 nm. The ability of most of the compounds to photocleave DNA was high at 312 nm, whereas higher concentrations were required at 365 nm as a result of their lower UV absorption. The affinity of selected compounds to calf-thymus (CT) DNA was studied by UV spectroscopy, viscosity experiments and competitive studies with ethidium bromide (EB) revealing that all compounds interacted with CT DNA. The fluorescence emission spectra of the pre-treated EB-DNA exhibited a moderate to significant quenching in the presence of the compounds indicating the binding of the compounds to CT DNA via intercalation as concluded also by DNA-viscosity experiments. For the oxime esters the DNA photocleavage and affinity studies aimed to clarify the role of the oxime nature (aldoxime, ketoxime, amidoxime) and the role of the pyridine and p-nitrophenyl moieties both as oxime substituents and ester conjugates.

Total synthesis of enantiopure potassium aeshynomate.

Potassium aeshynomate (1) is the leaf-opening factor of the nyctinastic plant Aeshynomene indica L. In this article a convenient and efficient strategy for the total synthesis of enantiomerically pure 1 is described, starting from the l-arabinose derived chiron ent-6. The realized synthetic scheme involves a postcoupling oxidation approach and securely determines the absolute configuration of the targeted natural product, which remained unknown until now.

Synthesis and cytotoxic evaluation of novel pyrimidine deoxyapiothionucleosides.

The synthesis of novel pyrimidine deoxyapiothionucleosides of D- and L-series was realized following application of a versatile and high-yielding scheme, which utilized inexpensive L- and D-arabinose as starting materials, respectively, and which makes use of a regio- and stereo-selective Pummerer rearrangement reaction for the coupling of the nucleobase with the thiosugar moiety. Some of the targeted compounds have shown selective cytotoxic effects (with IC50<10 µM) against specific cancer cell lines. All of the tested compounds had no cytotoxic effect on the normal cell line tested.

6-Nitro-Quinazolin-4(3H)-one Exhibits Photodynamic Effects and Photodegrades Human Melanoma Cell Lines. A Study on the Photoreactivity of Simple Quinazolin-4(3H)-ones.

Photochemo and photodynamic therapies are minimally invasive approaches for the treatment of cancers and powerful weapons for competing bacterial resistance to antibiotics. Synthetic and naturally occurring quinazolinones are considered privileged anticancer and antibacterial agents, with several of them to have emerged as commercially available drugs. In the present study, applying a single-step green microwave irradiation mediated protocol we have synthesized eleven quinazolinon-4(3H)-ones, from cheap readily available anthranilic acids, in very good yields and purity. These products were irradiated in the presence of pBR322 plasmid DNA under UVB, UVA and visible light. Four of the compounds proved to be very effective DNA photocleavers, at low concentrations, being time and concentration dependent as well as pH independent. Participation of reactive oxygen species was related to the substitution of quinazolinone derivatives. 6-Nitro-quinazolinone in combination with UVA irradiation was found to be in vitro photodestructive for three cell lines; glioblastoma (U87MG and T98G) and mainly melanoma (A-375). Thus, certain appropriately substituted quinazolinones may serve as new lead photosensitizers for the development of promising biotechnological applications and as novel photochemo and photodynamic therapeutics.

A short alternative preparation of the bengazoles polyol side-chain segment.

A new short and efficient synthesis of the bengazoles side chain is reported using a sequential Grignard addition-hydroboration approach on a readily available d-ribose derivative.

Trachycladines and Analogues: Synthesis and Evaluation of Anticancer Activity.

The synthesis of four new analogues of marine nucleoside trachycladine A was accomplished by direct regio- and stereoselective Vorbrüggen glycosylations of 2,6-dichloropurine and 2-chloropurine with a d-ribose-derived chiron. Naturally occurring trachycladines A and B and a series of analogues were examined for their cytotoxic activity against a number of cancer cell lines (glioblastoma, lung, and cervical cancer). Parent trachycladine A and two analogues (the diacetate of the 2,6-dichloropurine derivative and N-cyclopropyl trachycladine A) resulted in a significant decrease in cell viability, with the latter exhibiting a stronger effect. The same compounds enhanced the cytotoxic effect of docetaxel in lung cancer cell lines, whereas additional experiments revealed that their mode of action relies on mitotic catastrophe rather than DNA damage. Moreover, their activity as autophagic flux blockers was postulated.

Alkyl and aryl sulfonyl p-pyridine ethanone oximes are efficient DNA photo-cleavage agents.

Sulfonyloxyl radicals, readily generated upon UV irradiation of p-pyridine sulfonyl ethanone oxime derivatives, effectively cleave DNA, in a pH independent manner, and under either aerobic or anaerobic conditions. p-Pyridine sulfonyl ethanone oxime derivatives were synthesized from the reaction of p-pyridine ethanone oxime with the corresponding sulfonyl chlorides in good to excellent yields. All compounds, at a concentration of 100µM, were irradiated at 312nm for 15min, after incubation with supercoiled circular pBluescript KS II DNA and resulted in extended single- and double- strand cleavages. The cleavage ability was found to be concentration dependent, with some derivatives exhibiting activity even at nanomolar levels. Besides that, p-pyridine sulfonyl ethanone oxime derivatives showed good affinity to DNA, as it was observed with UV interaction and viscosity experiments with CT DNA and competitive studies with ethidium bromide. The compounds interact to CT DNA probably by non-classical intercalation (i.e. groove-binding) and at a second step they may intercalate within the DNA base pairs. The fluorescence emission spectra of pre-treated EB-DNA exhibited a significant or moderate quenching. Comparing with the known aryl carbonyloxyl radicals the sulfonyloxyl ones are more powerful, with both aryl and alkyl sulfonyl substituted derivatives to exhibit DNA photo-cleaving ability, in significantly lower concentrations. These properties may serve in the discovery of new leads for "on demand" biotechnological and medical applications.

Formation of new alkynyl(phenyl)iodonium salts and their use in the synthesis of phenylsulfonyl indenes and acetylenes.

The preparation of phenylsulfonyl indene derivatives and phenylsulfonyl- acetylenes from readily available alkynyl(phenyl)iodonium tetrafluoroborates and triflates was investigated using phenylsulfinate as nucleophile.

Total Synthesis of Vancomycin Aglycon-Part 2: Synthesis of Amino Acids 1-3 and Construction of the AB-COD-DOE Ring Skeleton.

A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies.

Total Synthesis of Vancomycin Aglycon-Part 3: Final Stages.

A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies.

Synthesis of stable aromatic and heteroaromatic sulfonyl-amidoximes and evaluation of their antioxidant and lipid peroxidation activity.

We describe herein the synthesis of stable aromatic and heteroaromatic sulfonyl-amidoximes, from the reaction of amidoximes with the corresponding sulfonyl chlorides, in low to excellent yields. Evaluation of their antioxidant activity has shown that 17 out of 28 compounds highly compete DMSO for hydroxyl radicals, while five of them inhibit lipid peroxidation. Combining the reducing and anti-lipid peroxidation ability it seems that compounds 13 and 31 could be used as lead molecules.

Tetrakisphosphates and bispyrophosphates of myo-inositol derivatives as allosteric effectors of human hemoglobin: Synthesis, molecular recognition, and oxygen release.

Various 2,5- and 1,4-substituted and unsubstituted myo-inositol tetrakisphosphates and bispyrophosphates were prepared following a general synthetic pathway. All final compounds were tested for their capability to induce oxygen release from human hemoglobin. Most of these proved to be efficient allosteric effectors, with similar affinities for hemoglobin to that of myo-inositol hexakisphosphate, which is one of the best known allosteric effectors of hemoglobin. The efficacy was found to be higher for free phosphates than pyrophosphates. As allosteric Hb effectors, these compounds enable enhanced oxygen release. These effects increase with the strength of Hb binding and correspond primarily to electrostatic interactions. Stereochemical and steric factors also play a significant but secondary role in molecular recognition. In view of the central role played by hypoxia in numerous types of diseases, the exploration of myo-inositol phosphate derivatives represents an important avenue in the search for substances which act on the oxygenation status of tissues and may have significant potential in the discovery and development of novel drug candidates.

Polyphosphates and pyrophosphates of hexopyranoses as allosteric effectors of human hemoglobin: synthesis, molecular recognition, and effect on oxygen release.

Polyphosphorylated and perphosphorylated hexopyranose monosaccharides and disaccharides were synthesized from parent or partially protected carbohydrates as potential allosteric effectors of hemoglobin. A study toward the construction of seven- and eight-membered cyclic pyrophosphates was also performed on the sugars which had the proper orientation, protection, and number of phosphates. All final compounds were tested for their efficiency on oxygen release from human hemoglobin. Several compounds presented higher potency than myo-inositol hexakisphosphate, which is the most efficient of the known allosteric effectors of hemoglobin. Structure-activity relationships were analyzed. The affinity and efficiency depend on the number of phosphates attached to the carbohydrate skeleton and are related primarily to the number of negative charges present. Other effects operate, but play a lesser role.

Polyphosphates and pyrophosphates of pentopyranoses and pentofuranoses as allosteric effectors of human hemoglobin: synthesis, molecular recognition, and oxygen release.

Perphosphorylated pentopyranoses and pentofuranoses were synthesized from parent carbohydrates as potential allosteric effectors of hemoglobin (Hb). The construction of seven- and eight-membered cyclic pyrophosphates was also carried out successfully on most of the pentoses. All final compounds were tested for their efficiency on oxygen release from human Hb. Most proved to be efficient allosteric effectors, some of them with an affinity toward Hb and an effect on oxygen release from Hb approaching that of myo-inositol hexakisphosphate, which is one of the most active allosteric effectors of Hb. The efficacy was higher for free phosphates than for pyrophosphates.