SYNTHESIS OF 3′-DEOXY-3′-C-HYDROXYMETHYL ANALOGUES OF TIAZOFURIN AND RIBAVIRIN

On the basis of potent biological activity of 3′-branched-3′-deoxynucleoside analogues, novel ribavirin and tiazofurin derivatives with 3′-C-hydroxymethyl substituent were synthesized, starting from D-xylose.     

THIOSUGARS. VIII.* PREPARATION OF NEW 4′-THIO-L-LYXO PYRIMIDINE NUCLEOSIDE ANALOGUES

Reaction of 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-L-lyxofuranose with silylated pyrimidine bases and subsequent deprotection with boron tribromide led to 4′-thio-L-lyxo pyrimidine nucleosides. The 5-bromo-6-methyl derivative was prepared from methyl 2,3,5-tri-O-acetyl-4-thio-L-lyxofuranoside. Deacetylation was performed with sodium methoxide. The anomers were separated by HPLC and their configurations assigned by NMR spectroscopy and X-ray structural analyses. The biological activity of the nucleosides was tested.

     

PREPARATION OF BASE-DEUTERATED 2′-DEOXYADENOSINE NUCLEOSIDES AND THEIR SITE-SPECIFIC INCORPORATION INTO DNA

We report a four-step synthesis of 2′-deoxy-2-deuteroadenosine from 2′-deoxyadenosine in 38% overall yield. The more accessible 2′-deoxy-8-deuteroadenosine was also prepared and incorporated into DNA by automated solid phase synthesis (80% deuterium) using N ⁶-benzoyl-2′-deoxy-8-deuteroadenosine-3′-O-(2-cyanoethyl-N,N-diisopropylphosphoramidite) in combination with acetyl-protected deoxycytidine and phenoxyacetyl-protected purine phosphoramidites.     

SYNTHESIS AND STUDY OF CONFORMATIONALLY RESTRICTED 3′-DEOXY-3′,4′-EXO-METHYLENE NUCLEOSIDE ANALOGUES

Hitherto unknown restricted 3′-deoxy-3′,4′-exo-methylene nucleoside derivatives bearing the nucleic acid naturally occurring pyrimidine bases have been synthesized. The compounds were tested for their activity against HIV, HBV, and several RNA viruses, but they did not show significant antiviral effect.     

SYNTHESIS AND ANTI-HIV ACTIVITY OF THYMIDINE ANALOGUES BEARING A 4′-CYANOVINYL GROUP AND SOME DERIVATIVES THEREOF

Treatment of 3′-O-tert-butyldimethylsilyl-2′,5′-dideoxy-5′-oxothymidine (4) with potassium or magnesium nitromethanide afforded in good yield the resolvable epimeric mixture of the expected blocked nitronucleosides 5 which upon dehydration led to the corresponding E-nitroenofuranosylthymidine 6. Nucleophilic attack of cyanide onto the nitrovinyl group led to a nucleoside analogue bearing a terminal 1-cyanovinyl group (7), a soft electrophilic group which, upon reaction with benzeneselenol, underwent a conjugate addition to the phenylselenonucleoside derivative 9. All these compounds, eventually de-O-silylated, were subject of in vitro biological testing, some exhibiting interesting cytotoxic or antiviral properties.     

SYNTHESIS OF 2′-C-METHYL-β-D-RIBOFURANOSYLIMIDAZO[4,5-D]PYRIDAZINE DERIVATIVES (2-AZA-3-DEAZAPURINE NUCLEOSIDE ANALOGUES)

In order to evaluate their antiviral properties, two imidazo[4,5-d]pyridazine 2-C-methyl-β-D-ribofuranonucleoside derivatives have been synthesized.     

MICROWAVE ASSISTED HIGH YIELDING PREPARATION OF N-PROTECTED 2′-DEOXYRIBONUCLEOSIDES USEFUL FOR OLIGONUCLEOTIDE SYNTHESIS

ABSTRACT

A rapid and high yielding method for the synthesis of precursors of synthons for DNA synthesis, N-protected 2′-deoxyribonucleosides is described, which occur under mild conditions using microwave irradiation. The desired material, N-protected nucleosides, was obtained in 93–96% yield in few minutes. The final products were then characterized by ¹H-NMR and MALDI-TOF and compared with the standard samples. The method is amenable to small to moderate scale of synthesis.     

SYNTHESIS OF 5-METHYLAMINO-2′-DEOXYURIDINE DERIVATIVES

Reductive amination of 3′,5′-O-(tetraisopropyldisilyloxane-1,3-diyl)-2′-deoxy-5-formyluridine with several aliphatic and aromatic amines, in various solvents, is described. In the case of aliphatic amines, the expected C-5 substituted methylamino pyrimidine nucleosides are formed along with by-products deriving from opening of the pyrimidine ring. Relative amounts of the by-products depend upon the polarity of the solvent employed.     

SYNTHESIS AND ANTIVIRAL EVALUATION OF C-4-HYDRAZIDE DERIVATIVES OF 2′,3′-DIDEOXYCYTIDINE

Syntheses of three hitherto unknown derivatives of 2′,3′-dideoxycytidine, namely C-4-(salicylic hydrazide)-ddC, C-4-(N-butyloxycarbonyl-isoleucine hydrazide)-ddC and its N-unprotected chlorhydrate salt have been carried out. These compounds do not induce inhibition of HIV-1 replication in cell culture experiments. Nevertheless, the modifications on the base moiety increased in all cases the lipophilicity of the parent molecule with an acceptable water solubility compared to ddC.     

SULFOXIDE-METAL EXCHANGE FOR THE SYNTHESIS OF THE 2′-TRIBUTYLSTANNYL DERIVATIVE OF 2′,3′-DIDEHYDRO-2′,3′-DIDEOXYURIDINE (d4U): A GENERAL ENTRY TO 2′-CARBON-SUBSTITUTED ANALOGUES OF d4U

ABSTRACT

Methods are described for the synthesis of the 2′-tributylstannyl derivative of 2′,3′-didehydro-2′, 3′-dideoxyuridine (d4U). Two approaches were investigated: radical-mediated desulfonylative stannylation of the 2′-benzenesulfonyl derivative of d4U and sulfoxide-metal exchange reaction of the 2′-benzenesulfinyl derivative. The latter approach was found to give the desired 2′-stannyl derivative in good yield. It was also shown that manipulations of the stannyl group allowed the introduction of a variety of carbon-substituents to the 2′-position by applying the Stille reaction. The whole reaction sequence has opened up a highly general entry to 2′-carbon-substituted analogues of d4U.     

SYNTHESIS OF 3′-UREIDOADENOSINE ANALOGUES AND THEIR BINDING AFFINITY TO THE A3 ADENOSINE RECEPTOR

Novel 3′-ureidoadenosine analogues were synthesized from 1,2:5,6-di-O-isopropylidene-D-glucose in order to lead to stronger hydrogen bonding at the A₃ adenosine receptor than the corresponding 3′-aminoadenosine derivatives. However, all synthesized 3′-ureidoadenosine analogues have lost their binding affinities to the all subtypes of adenosine receptors, indicating that bulky 3′-urea moiety led to conformational distortion.     

EFFICIENT SYNTHESIS OF D-[1′-13C]-RIBONUCLEOSIDES FOR INCORPORATION INTO OLIGO-RNA

Syntheses of the monomer building blocks used for the solid-phase synthesis of specifically 1′-¹³C-labeled oligoribonucleotides from the D-[1-¹³C]ribose is presented. Procedure has been used for the selective formation of 2′-O-silylated ribonucleosides. After 5′-O-dimethoxytritylation, the synthesis of D-[1′-¹³C] ribonucleoside phosphoramidites has been achieved.     

SYNTHESIS OF CERTAIN 2′-DEOXYURIDINE DERIVATIVES CONTAINING SUBSTITUTED PHENOXY GROUPS ATTACHED TO C-5′; EVALUATION AS POTENTIAL dUTP ANALOGUES

Derivatives of 2′-deoxyuridine in which the 5′-OH group is replaced by a 2,3,6-trifluoro-5-hydroxy-4-nitrophenoxy or a 4-carboxy-2,3,6-trifluoro-5-hydroxyphenoxy group have been prepared for evaluation as possible dUTP analogues. They showed a weak ability to displace radiolabelled dUTP from a dUTP-binding antiserum. The corresponding compounds lacking the three fluorine substituents were prepared for comparison.     

MICROWAVES SYNTHESIS OF SOLID SUPPORTS FOR THE SYNTHESIS OF 3′-AMINOALKYL OLIGODEOXYNUCLEOTIDES

Phthalimido-alkyl alcohol solid supports were rapidly prepared from solid supported phthalic anhydride and amino alcohol condensation induced by microwaves. These supports were used to synthesize 3′-aminoalkyl oligodeoxynucleotides allowing a two step deprotection necessary to avoid aminolink alkylation.     

STRUCTURE-ACTIVITY RELATIONSHIP OF 5′-SUBSTITUTED FLUORO-NEPLANOCIN A ANALOGUES AS POTENT INHIBITORS OF S-ADENOSYLHOMOCYSTEINE HYDROLASE

Four 5′-substituted fluoro-neplanocin A analogues 1a–d were designed and synthesized, and the inhibitory activity against SAH was in the following order: NH₂ > SH > F, N₃, indicating a hydrogen bonding donor is essential for inhibitory activity.     

SYNTHESIS OF CARBOCYCLIC ANALOGS OF 2′,3′-DIDEOXYSANGIVAMYCIN, 2′,3′-DIDEOXYTOYOCAMYCIN,AND 2′,3′-DIDEOXYTRICIRIBINE

Syntheses and antiviral activity of new carbocyclic analogs of 2′, 3′-dideoxysangivamycin, 2′,3′-dideoxytoyocamycin and 2′,3′-dideoxytriciribine is described. The key intermediate, carbocyclic 4-chloro- 5-iodopyrrolopyrimidine, was synthesized in good yield via a novel iodination method using I₂ and CF₃COOAg. This carbocyclic 4-chloro-5-iodopyrrolopyrimidine then allowed for a concise synthesis of the desired 4,5-disubstituted carbocyclic nucleosides.     

PREPARATION OF OLIGODEOXYNUCLEOTIDE 5′-TRIPHOSPHATES USING SOLID SUPPORT APPROACH

We report a synthetic procedure for conversion of oligonucleotides to their 5′-triphosphate derivatives with moderate yield. The oligonucleotides were synthesized on solid support using standard phosphoramidite protocols. The DMT protection group was removed and the 5′-OH was phosphitylated using 2-chloro-4H-1,3,2-benzodioxaphosphorin-4-one followed by reaction with tributyammonium pyrophosphate and iodine oxidation. After subsequent removal from support and complete deprotection, the products were isolated by anion-exchange HPLC chromatography. Structures of several 5′-triphosphate derivatives have been proven by phosphorus NMR, Mass-spectrometry and by HPLC comparison with authentic samples.     

3′-DEOXYRIBOFURANOSE DERIVATIVES OF 1-DEAZA AND 3-DEAZA-ADENOSINE AND THEIR ACTIVITY AS ADENOSINE DEAMINASE INHIBITORS

2,6-Dichloro-1-deazapurine and 2,6-dichloro-3-deazapurine were coupled with 1,2-O-diacetyl-5-O-benzoyl-3-deoxy-β-D-ribofuranose. Deprotection of the obtained compounds and reaction with liquid ammonia gave the desired 2-chloroadenine nucleosides, which were dechlorinated to afford the corresponding 1-deaza and 3-deazaadenosine derivatives. Biological studies performed on ADA from calf intestine showed that these new nucleosides are inhibitors of the enzyme.     

SYNTHESIS AND ANTIVIRAL EVALUATION OF 3′-C-TRIFLUOROMETHYL NUCLEOSIDE DERIVATIVES BEARING ADENINE AS THE BASE

3′-deoxy-3′-C-trifluoromethyl- (3), 2′,3′-dideoxy-3′-C-trifluoromethyl- (5) and 2′,3′-dideoxy-2′,3′-didehydro-3′-C-trifluoromethyladenosine (6) derivatives have been synthesized and their antiviral properties examined. All these derivatives were stereospecifically prepared by glycosylation of adenine with a trifluoromethyl sugar precursor (1), followed by appropriate chemical modifications. The prepared compounds were tested for their activity against HIV, but they did not show an antiviral effect.     

EFFICIENT PRODUCTION OF URIDINE 5′-DIPHOSPHO-N-ACETYLGLUCOSAMINE BY THE COMBINATION OF THREE RECOMBINANT ENZYMES AND YEAST CELLS

Uridine 5′-diphospho N-acetylglucosamine (UDP-GlcNAc) is an important nucleotide sugar in the biochemistry of all living organisms, and it is an important substrate in the synthesis of oligosaccharides. In the present work, three bioactive enzymes, namely, glucokinase (YqgR), GlcNAc-phosphate mutase (Agm1), and N-acetylglucosamine-1-phosphate uridyltransferase (GlmU), were produced effectively as soluble form in recombinant Escherichia coli. These three enzymes and dried yeast together were used to construct a multistep enzymatic system, which could produce UDP-GlcNAc efficiently with N-acetylglucosamine (GlcNAc) as the substrate. After the optimization of various reaction conditions, 31.5 mMUDP-GlcNAc was produced from 50 mMGlcNAc and 50 mMUMP.