Milena Masojídková

Synthesis of branched 9-[2-(2-phosphonoethoxy)ethyl]purines as a new class of acyclic nucleoside phosphonates which inhibit Plasmodium falciparum hypoxanthine–guanine–xanthine phosphoribosyltransferase

The malarial parasite Plasmodium falciparum (Pf) lacks the de novo pathway and relies on the salvage enzyme, hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT), for the synthesis of the 6-oxopurine nucleoside monophosphates. Specific acyclic nucleoside phosphonates (ANPs) inhibit PfHGXPRT and possess anti-plasmodial activity. Two series of novel branched ANPs derived from 9-[2-(2-phosphonoethoxy)ethyl]purines were synthesized to investigate their inhibition of PfHGXPRT and human HGPRT. The best inhibitor of PfHGXPRT has a K(i) of 1 microM. The data showed that both the position and nature of the hydrophobic substituent change the potency and selectivity of the ANPs.

Antiviral activity of triazine analogues of 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (cidofovir) and related compounds.

Treatment of 5-azacytosine sodium salt with diisopropyl [(2-chloroethoxy)methyl]phosphonate followed by removal of ester groups with BrSi(CH3)3 afforded 1-[2-(phosphonomethoxy)ethyl]-5-azacytosine (3). Reaction of 5-azacytosine with [(trityloxy)methyl]-(2S)-oxirane followed by etherification with diisopropyl (bromomethyl)phosphonate and removal of ester groups gave 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (1). The synthesis of 6-azacytosine congener 2 was analogous using N4-benzoylated intermediates. Compound 1 was shown to exert strong activity against a broad spectrum of DNA viruses including adenoviruses, poxviruses, and herpesviruses (i.e., herpes simplex viruses, varicella zoster virus, and human cytomegalovirus). Decomposition of 1 in alkaline solutions resulted in products 17 and 18. While the N-formylguanidine derivative 17 proved active, the carbamyolguanidine derivative 18 was devoid of antiviral activity.

Acyclic Nucleoside Bisphosphonates: Synthesis and Properties of Chiral 2-Amino-4,6-bis[(phosphonomethoxy)alkoxy]pyrimidines

2-Amino-4,6-bis[(phosphonomethoxy)alkoxy]pyrimidines bearing two equal or different achiral or chiral phosphonoalkoxy chains have been prepared either by aromatic nucleophilic substitution of 2-amino-4,6-dichloropyrimidine or by alkylation of 4,6-dihydroxy-2-(methylsulfanyl)pyrimidine with appropriate phosphonate-bearing building block. Alkylation of 4,6-dihydroxy-2-(methylsulfanyl)pyrimidine proved to be the method of choice for efficient preparation of variety of bisphosphonates. The enantiomeric purity of selected compounds was determined by capillary electrophoresis. Antiviral activity of bisphosphonates is discussed.

Geminal hydroxy phosphonate derivatives of nucleosides: A novel class of nucleoside 5′-monophosphate analogues

Abstract A novel type of phosphonate-based, isopolar, nonisosteric 5′-nucleotide analogue, the nucleoside 5′-hydroxy phosphonates, was prepared by Abramov nucleophilic addition of various phosphorous acid esters to nucleoside 5′-aldehydes. The newly formed compounds are distinguished by chirality of the 5′-carbon atom. The configuration of the 5′-epimers was assigned from NMR spectra.

Synthesis of ester prodrugs of 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-2,6-diaminopurine (HPMPDAP) as anti-poxvirus agents.

9-(S)-[3-Hydroxy-2-(phosphonomethoxy)propyl]-2,6-diaminopurine (HPMPDAP) and its cyclic form were selected for further evaluation as potential drug candidates against poxvirus infections. To increase bioavailability of these compounds, synthesis of their structurally diverse ester prodrugs was carried out: alkoxyalkyl (hexadecyloxypropyl, octadecyloxyethyl, hexadecyloxyethyl), pivaloyloxymethyl (POM), 2,2,2-trifluoroethyl, butylsalicylyl, and prodrugs based on peptidomimetics. Most HPMPDAP prodrugs were synthesized in the form of monoesters as well as the corresponding cyclic phosphonate esters. The activity was evaluated not only against vaccinia virus but also against different herpes viruses. The most potent and active prodrugs against vaccinia virus were the alkoxyalkyl ester derivatives of HPMPDAP, with 50% effective concentrations 400-600-fold lower than those of the parent compound. Prodrugs based on peptidomimetics, the 2,2,2-trifluoroethyl, the POM, and the butylsalicylyl derivatives, were able to inhibit vaccinia virus replication at 50% effective concentrations that were equivalent or ∼10-fold lower than those observed for the parent compounds.

Acyclic nucleoside phosphonates with 5-azacytosine base moiety substituted in C-6 position.

Two methods for preparation of 6-substituted derivatives of anti DNA-viral agent 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (HPMP-5-azaC) were developed: (1) ammonia mediated ring-opening reaction of diisopropyl esters of HPMP-5-azaC (4) to carbamoylguanidine derivatives followed by ring-closure reaction with orthoesters and (2) condensation reaction of 6-substituted 5-azacytosines with diisopropyl (1S)-[2-hydroxy-1-tosyloxymethyl)ethoxy]methylphosphonate (15). Deprotection of diisopropyl esters to free phosphonic acids was performed with bromotrimethylsilane in acetonitrile followed by hydrolysis. In contrast to parent compound HPMP-5-azaC, a substantial decrease of antiviral activity in case of 6-substituted analogues occurred. Surprisingly, N-3 isomer of 6-methyl-HPMP-5-azaC in the form of isopropyl ester revealed activity against RNA viruses (Sindbis virus).

2′,3′-O-Phosphonoalkylidene derivatives of ribonucleosides: Synthesis and reactivity

Abstract A novel type of nucleotide analogues, the 2′,3′-O-(1-diethylphosphono)alkylidene derivatives of ribonucleosides was prepared by redox reaction of diethyl chlorophosphite with various nucleoside orthoesters. Some of these compounds undergo interesting rearrangements when treated with nucleophiles. The configuration of the title compounds was determined by 2D-ROESY experiments. Biological activity of partially protected nucleotide analogues is also discussed.

SYNTHESIS OF ACYCLIC NUCLEOTIDE ANALOGUES DERIVED FROM N-SUBSTITUTED 6-(1-AMINOETHYL)PURINES VIA 6-ACETYLPURINE DERIVATIVES

Abstract The Stille coupling of 9-2-[bis(2-propoxy)phosphonylmethoxy]ethyl-6-chloropurines with 1-(ethoxyvinyl)tributyltin afforded 6-(1-ethoxyvinyl)purine derivatives. Their acid hydrolysis gave 6-acetylpurine derivatives that after reductive amination using various primary and secondary amine hydrochlorides and sodium cyanoborohydride followed by deprotection afforded the title N-substituted 6-(1-aminoethyl)-9-(2-phosphonomethoxyethyl)purine derivatives.

3′,5′-O-Phosphonoalkylidene derivatives of 1-(2-deoxy-β-D-threo-pentofuranosyl)thymine: Synthesis and reactivity

Abstract Various 3′,5′-O-(1-phosphonoalkylidene) derivatives of 1-(2-deoxy-β-D- threo -pentofuranosyl)thymine bearing a substituent in the ω-position of the alkylidene chain were prepared by the redox reaction of diethyl chlorophosphite with six-membered 3′,5′-orthoesters of xylo -dT. Susceptibility of ω-haloalkylidene derivatives for nucleophilic substitution is discussed. The configuration of the final phosphonates was determined by 2D-ROESY NMR experiments.

Nucleosidyl-O-Methylphosphonates: a pool of monomers for modified oligonucleotides.

An unique set of 5′‐O‐ and 3′‐O‐phosphonomethyl derivatives of four natural 2′‐deoxyribonucleosides, 1‐(2‐deoxy‐β‐D‐threo‐pentofuranosyl)thymine, 5′‐O‐ and 2′‐O‐phosphonomethyl derivatives of 1‐(3‐deoxy‐β‐D‐erythro‐pentofuranosyl)thymine, and 1‐(3‐deoxy‐β‐D‐threo‐pentofuranosyl)thymine has been synthesized as a pool of monomers for the synthesis of modified oligonucleotides. The phosphonate moiety was protected with 4‐methoxy‐1‐oxido‐2‐pyridylmethyl ester group, serving also as an intramolecular catalyst in the coupling step.