Pavol Kois

OLIGONUCLEOTIDES WITH ISOPOLAR PHOSPHONATE INTERNUCLEOTIDE LINKAGE: A NEW PERSPECTIVE FOR ANTISENSE COMPOUNDS?

Several types of isopolar modified oligothymidylates and oligoadenylates (15 mers) with the phosphonate -O-P-CH 2-O- internucleotide linkage were prepared. The modified oligonucleotides were subjected to the study of their hybridization properties, resistance against nucleases, and the ability to elicit RNase H activity.

Synthesis of coumarin or ferrocene labeled nucleosides via Staudinger ligation

Background Reaction of azides with triaryl phosphines under mild conditions gives iminophosphoranes which can react with almost any kind of electrophilic reagent, e.g. aldehydes/ketones to form imines or esters to form amides. This so-called Staudinger ligation has been employed in a wide range of applications as a general tool for bioconjugation including specific labeling of nucleic acids. Results A new approach for the preparation of labeled nucleosides via intermolecular Staudinger ligation is described. Reaction of azidonucleosides with triphenylphosphine lead to iminophosphorane intermediates, which react subsequently with derivatives of coumarin or ferrocene to form coumarin or ferrocene labeled nucleosides. Fluorescent properties of coumarin labeled nucleosides are determined. Conclusion New coumarin and ferrocene labeled nucleosides were prepared via intermolecular Staudinger ligation. This reaction joins the fluorescent coumarin and biospecific nucleoside to the new molecule with promising fluorescent and electrochemical properties. The isolated yields of products depend on the structure of azidonucleoside and carboxylic acids. A detailed study of the kinetics of the Staudinger ligation with nucleoside substrates is in progress.

3-Formylchromones IV. The Rearrangement of 3-Formylchromone Enamines as a Simple, Facile Route to Novel Pyrazolo[3,4-b]pyridines and the Synthetic Utility of the Latter

One-pot and facile preparations of 6-(2-hydroxy-5-R-benzoyl)-4-methyl-2-R1- pyrazolo[3,4-b]pyridines 4a-o are described, using the reaction of 3-formyl chromones 1 with 5-amino-1-R1-pyrazoles 2. An enamine-intermediate 2-ethyloxy-6-R-3-(3-methyl-1- phenylpyrazol-5-ylaminomethylene)chroman-4-one 3 was isolated at lower temperatures. Acyloxy-derivatives 5 of compounds 4 were obtained by acylation with acid chlorides or acid anhydrides. Coumarins 6 substituted at the 3- and 4-positions were prepared from the pyrazolo[3,4-b]pyridines 4 by condensation reactions and hydrazones 7 were formed from their reaction with 2,4-dinitrophenyl hydrazine. Reactions under microwave irradiation proceeded significantly faster and with high yields.

Peculiarities of the Interaction of Short Oligonucleotides with Supported Lipid Films and Langmuir Monolayers

Summary. The method of electrostriction was applied to supported bilayer lipid membranes (sBLM) and Langmuir monolayers with the aim to study the peculiarities of the interaction of short oligonucleotides with lipid films and of the duplex formation between complementary oligonucleotides. The bilayer lipid membranes (sBLM) were formed on an agar support, whereas Langmuir monolayers were generated on the air-water interface. As an oligonucleotide, the 15-mer 5′-cholesterolphosphoryl-dT15 (CHpdT15) was synthesized. We could show that the interaction of CHpdT15 with sBLM resulted in a considerable increase of the elasticity modulus perpendicular to the membrane plane (E⊥) and an increase of the surface potential. Interaction of complementary oligodeoxyadenylate (dA15) with sBLM modified by CHpdT15 resulted in a slight increase of the surface potential whereas E⊥ slightly decreased. CHpdT15 forms monomolecular layers on the air/water interface. Interaction of dA15 with such monolayers resulted in an increase of the surface pressure, probably due to an increase of the surface charge of the monolayer; similar effects were observed for lipid monolayers modified by CHpdT15. Prospects of using such interactions for detecting DNA hybridization are discussed.

DNA fragment separations by on-line combination of capillary isotachophoresis – capillary zone electrophoresis with UV detection

A high‐speed DNA fragment separation system based on an on‐line combination of capillary ITP with CZE (CITP‐CZE) and using UV detection at 260 nm was developed. A novel CITP‐CZE buffer system of pH 6.1 was designed for the separation of ten DNA fragments with sizes ranging from 100 to 1000 bp. An effect of underivatized α‐, β‐ and γ‐cyclodextrins on the resolution of DNA fragments in the CZE step of the CITP‐CZE combination was systematically investigated. Methylhydroxyethylcellulose present in the BGE was used to eliminate the EOF. DNA ladder fragments were separated within 10 min with LODs in the range of 1–5 ng/μL (S/N = 3). The RSDs of the migration time and peak area of individual DNA fragments were in the range of 1–3 and 3–9%, respectively. The developed CITP‐CZE system was further applied to the analysis of digest plasmid DNA samples.

Expression of soluble Saccharomyces cerevisiae alcohol dehydrogenase in Escherichia coli applicable to oxido-reduction bioconversions

Six-carbon aldehydes and alcohols belong to flavours and fragrances with wide application in the food, feed, cosmetic, chemical and pharmaceutical sectors. In the present study, we prepared the expression system for production of recombinant yeast alcohol dehydrogenase 1 (YADH1) from Saccharomyces cerevisiae which is suitable also for catalysis of the interconversion of C-6 aldehydes and alcohols. We have demonstrated that an effective three-step strategy can overcome the insolubility problems during YADH1 production in Escherichia coli. We used trxB and gor deficient expression strain, decreased concentration of isopropyl β-D-1-thiogalactopyranoside and lowered temperature to 20°C during induction. Finally, kinetic parameters of recombinant YADH1 were determined and we concluded it is a promising enzyme also for the interconversion of C-6 alcohols/aldehydes in green note volatile production.

Synthesis, reactions and antineoplastic activity of 3-(2-oxo-2H-chromen-3-yl)-2-oxo-2H,5H-pyrano[3,2-c]chromene derivatives

AbstractThe key 3-(2-oxo-2H-chromen-3-yl)-2-oxo-2H,5H-pyrano[3,2-c]chromen-5-yl acetates 3 were synthesized in high yields by cyclocondensation of 4-oxo-4H-chromen-3-carbaldehydes 1 with coumarin-3-acetic acids 2 under mild conditions. The reaction pathway involves aldol condensation and subsequent intramolecular lactonization to afford 2-oxo-2H,5H-pyrano[3,2-c]chromene skeleton 3. Further treatment of acetates 3 with alcohols, water or nitrogen containing compounds led to 5-alkoxy-, 5-hydroxy- or 5-acylamino-2H,5H-pyrano[3,2-c]chromen-2-ones 4-6via nucleophilic substitution of acetyloxy group at C-5. Acetates and hydroxyl derivatives 3 and 5 undergo facile rearrangement in an acid medium yielding 5-hydroxypyrano[2,3-b]chromen-2(10aH)-ones 7. Twelve prepared compounds were evaluated on their antineoplastic activities on 60 human tumour cell line panels in NCI USA. The obtained biological results confirmed that 3-(2-oxo-2H-chromen-3-yl)-2H,5H-pyrano[3,2-c]chromen-2-one represents a new leading skeleton suitable for further antitumour activity study.

A novel and efficient synthesis of 3-aryl-5-(2-hydroxybenzoyl)pyridin-2(1H)-ones by re-cyclization of N-(oxopyranochromenyl)acetamides and their antineoplastic screening

We have developed a novel, simple and efficient methodology for preparation of yet unknown 3-aryl-5-(2-hydroxybenzoyl)pyridin-2(1H)-ones 3(a–g) by EtONa driven re-cyclization of N-(3-aryl-2-oxo-2,5-dihydropyrano[3,2-c]chromen-5-yl)acetamides 2(a–g) in good yields (80–95%). A mechanism for this reaction was proposed. The 3-aryl-2-oxo-2,5-dihydropyrano[3,2-c]chromen-5-yl acetates 1(a–g) were prepared by cyclocondensation from 3-formylchromones (4-oxo-4H-chromene-3-carbaldehydes) and acetic acids in 64–86% yields. Acetamides 2(a–g) were obtained by reaction of 3-aryl-2-oxo-2,5-dihydropyrano[3,2-c]chromen-5-yl acetates 1(a–g) with AcNH2 catalyzed by pTsOH in 80–93% yields. Click chemistry precursors 4(a,d) and 5(a,d) were prepared by propargylation of 3(a,d) in 92–98% yields. They can serve for construction of more complex molecules possessing pyridone skeleton of 3. Eleventh novel compounds 3(a–g), 4(a,d) and 5(a,d) were screened on their anticancer activity on a panel of human tumour cell lines by NCI USA. We found that pyridones 3–5 selectively inhibit the growth of some of the tumour cell lines at 10−5 M (up to -33% compared to a control). The most sensitive tumour cell lines originated from kidney, breast, skin, ovary, blood and lung.Graphical Abstract

2 H -Pyrano[3,2- c ]quinolin-2-ones: their convenient synthesis and selected reactions

Despite the structure attractiveness of 2H-pyrano[3,2-c]quinolin-2-ones 3 their synthesis is not sufficiently developed. Only 35 pyranoquinolinones 3 are registered in the SciFinder database. Unavailability of 3 limits their chemistry exploitation, physical and biological studies. We have developed a convenient and general methodology for the synthesis of 3. Sixteen novel 2H-pyrano[3,2-c]quinolin-2-ones 3 were prepared by a cyclocondensation of easily available 4-oxo-1,4-dihydroquinoline-3-carbaldehydes 1 with monosubstituted acetic acids 2 (-aryl, -arylthio and -heteroaryl). To support chemistry exploitation of pyranoquinolinones 3, oxoquinolinylphenylacrylic acids 4 were obtained by hydrolysis of 3 with NaOH (92–98%). A simple oxidation of 3 by MCPBA was performed to provide oxopyranoquinoline N-oxide 5 (71%). Convenient rearrangement of 5 in refluxing Ac2O curried out 2H-pyrano[3,2-c]quinoline-2,5(6H)-dione 6 in 87% yield. Moreover, some of the prepared pyranoquinolinones 3 possess intensive blue fluorescence properties. Here we described the simple and general synthesis that allows availability of 2H-pyrano[3,2-c]quinolin-2-ones 3. Some transformations of 3 to the novel heterocyclic compounds 4–6 were performed as well in good yields (71–98%). The synthesis of 6 from 3 was not yet described. The developed methodology for the synthesis of 3–6 can stimulate their further physical and pharmacological studies.Graphical Abstract