Stereocontrolled Facile Synthesis and Biological Evaluation of (3′S) and (3′R)-3′-Amino (and Azido)-3′-Deoxy Pyranonucleosides

This article describes the synthesis of (3 ′S) and (3 ′R)-3 ′-amino-3 ′-deoxy pyranonucleosides and their precursors (3 ′S) and (3 ′R)-3 ′-azido-3 ′-deoxy pyranonucleosides. Azidation of 1,2:5,6-di-O-isopropylidene-3-O-toluenesulfonyl-α-D-allofuranose followed by hydrolysis and subsequent acetylation afforded 3-azido-3-deoxy-1,2,4,6-tetra-O-acetyl-D-glucopyranose, which upon coupling with the proper silylated bases, deacetylation, and catalytic hydrogenation, obtained the target 3 ′-amino-3 ′-deoxy-β-D-glucopyranonucleosides. The desired 1-(3 ′-amino-3 ′-deoxy-β-D-allopyranosyl)5-fluorouracil was readily prepared from the suitable imidazylate sugar after azidation followed by a protection/deprotection sequence and reduction of the unprotected azido precursor. No antiviral activity was observed for the novel nucleosides. Moderate cytostatic activity was recorded for the 5-fluorouracil derivatives.     

HYDROLYSIS OF 2′-DEOXY AND 2′-FLUORONUCLEOSIDE-3′-PHOSPHODlESTERS

Abstract

Two nucleoside analogs were synthesized to test the ribose conformational and electronic effects on phosphate hydrolysis at the 3′ position. It was found that under alkaline conditions, a 2′-fluoro-nucleoside (C3′-endo) resulted in a phosphate degradation that was ten times faster than the 2′-deoxynucleoside analog (C2′-endo). In addition to kinetic differences, product distributions will be presented.     

INACTIVATION OF S-ADENOSYL-L-HOMOCYSTEINE HYDROLASE WITH FLUORINATED ANALOGS OF 2′- AND 3′-DEOXY-5′-METHYLTHIOADENOSINE

Fluorinated analogs of 2′- and 3′-deoxy-5′-methylthioadenosine 1–4 caused irreversible inactivation of AdoHcy hydrolase. Based on the ESI-Mass spectra analysis of the inactivated enzyme with the fluorinated analog 1 a mechanism of inactivation is proposed.     

SYNTHESIS OF SOME 2′-FLUORO-2′-DEOXY-3′-C-ETHYNYL AND 3′-C-VINYL-β-D-LYXOFURANOSYL NUCLEOSIDES

1-(2-Fluoro-2-deoxy-β-D-arabinofuranosyl)uracil (5) and 1-(2-fluoro-2-deoxy-β-D-arabinofuranosyl)cytosine (6) were synthesized as reported earlier. Both of these compounds were converted into 2′-fluoro-2′-deoxy-3′-C-ethynyl and 3′-C-vinyl-β-D-lyxofuranosyl nucleosides (16–19) by a multistep sequence. All these new nucleosides were evaluated against seven human tumor cell lines in vitro.     

SYNTHESIS AND BIOLOGICAL EVALUATION OF CONFORMATIONALLY RESTRICTED AND NUCLEOBASE-MODIFIED ANALOGS OF THE ANTICANCER COMPOUND 3′-C-ETHYNYLCYTIDINE (ECYD)

A series of conformationally restricted and nucleobase-modified analogs of the anticancer compound 3′-C-ethynylcytidine (ECyd) and its uracil analog (EUrd) have been synthesized. While none of, the conformationally restricted analogs displayed anticancer activity, 5-iodo-EUrd and 5-bromo-EUrd displayed potent anticancer activity with IC50 values of 35 nM and 0.73 μM.     

Oligomerization of 3′-amino-3′-deoxyguanosine-5′-phosphorimidazolidate on a d(CpCpCpCpC) template

Summary 3-Amino-3-deoxyguanosine-5-phosphorimidazolidate (ImpGnh ₂) oligomerizes more rapidly and regiospecifically than related nucleotide derivatives on a d(CpCpCpCpC) template. The greater nucleophilicity of the amino group leads to efficient oligomerization even when the structure of the double-helical complex formed by the template and the substrate is not optimal for reaction. The use of amine-containing analogues should permit us to develop models of potentially prebiotic polymerization reactions that cannot be studied easily using natural nucleotides.     

利用~1H-NMR模拟谱研究三核苷酸A3′P(CH_3)5′A3′P(CH_3)5′A的构象性质

根据Altona等人的方法.利用~1H—NMR模拟谱分析了A3′P(CH_3)5A3′P(CH_3)5′A的三种非对映异构体:a、b和C的构象状态.发现:在室温下三个核糖环都是S型构象占优势(X_N≤0.44),而且随温度升高S型构象成分增多;两个二核苷酸片段-PAPA和APAP-的磷酸骨架扭角分别与A3′P(CH_3)5′A两种异构体a或b数值接近.差值约5°左右;二核苷酸片段中核糖环的重叠程度与手性磷原子的构型有关、R构型比S构型的核糖环重叠程度小;从而推测,A3′P(CH_3)5′A3′P(CH_3)5′A各种非对映异构体的稳定性为RR>RS.SR>SS,与化学合成中所见相符合.     

Electrochemical Analysis of 3′-Azidothymidine (AZT)

Abstract

3′-Azido-3′-deoxythymidine (AZT) exhibits a two-electron diffusion—controlled polarographic reduction wave, with conversion to 3^′?amino-3′-deoxythymidine. The mechanism of reduction, analytical and clinical applications, and its use for one-step synthesis of amino from azido nucleosides, are described.     

P-CHIRAL OLIGONUCLEOTIDES. 2D ROESY NMR ASSIGNMENT OF ABSOLUTE CONFIGURATION AT PHOSPHORUS AND CONFORMATIONAL ANALYSIS OF 5′-O-MONOMETHOXYTRITYL-(2′-O-DEOXYRIBONUCLEOSIDE) 3′-O-[O-(4-NITROPHENYL)]METHANEPHOSPHONATES

ABSTRACT

Fast and simple methodology for the assignment of the absolute configuration at the phosphorus atom in diastereomerically pure R_P and S_P 5′-O-monomethoxytrityl-2′-O-deoxynucleoside 3′-O-(O-4-nitrophenyl)methanephosphonate (3) was established. The method utilizes 2D ROESY NMR and can be used for the stereochemical analysis of other P-chiral mononucleotides. Configurational analysis shows that the major conformation of the sugar residue in 3 is of the S (South) type. This study will facilitate synthesis of stereoregular methylphosphonate oligonucleotide analogues via the transesterification method.     

THE NMR CONFORMATION STUDY OF THE COMPLEXES OF DEOXYCYTIDINE KINASE (dCK) AND 2′-DEOXYCYTIDINE/2′-DEOXYADENOSINE

The structures of the bound ¹³C/²H double-labelled 2′(R/S), 5′(R/S)-²H₂-1′,2′,3′,4′,5′-¹³C₅-2′-deoxyadenosine and the corresponding 2′-deoxycytidine moieties in the complexes with human deoxycytidine kinase (dCK) have been characterized for the first time by the solution NMR spectroscopy, using Transferred Dipole-Dipole Cross-correlated Relaxation and Transferred nOe experiments. It has been shown that the ligand adopts a South-type sugar conformation when bound to dCK.     

REACTION OF N3-BENZOYL-3′,5′-O-(DI-TERT-BUTYLSILANEDIYL)URIDINE WITH HINDERED ELECTROPHILES: INTERMOLECULAR N3 To 2′-O PROTECTING GROUP TRANSFER

ABSTRACT

The compound N³-benzoyl-3′,5′-O-(di-tert-butylsilanediyl)uridine 2 was alkylated with various alkyl iodides in CH₃CN in the presence of base. Normal 2′-O-alkylated products were obtained with methyl or benzyl iodide. if hindered alkyl iodides with β-branching such as 2-ethylbutyl iodide were used as electrophiles under the same conditions, N³-alkyl-2′-O-benzoyl uridine derivatives were produced. This unexpected transformation is usually dormant with reactive alkylating agents, but expressed with sterically hindered, less reactive electrophiles. This unwanted reaction gives isomeric products whose spectra differ in only subtle ways from target compounds.     

Phosphonoformate Esters of Anti-HIV Nucleosides: 3′-Azido-3′-deoxythymidine and 2′,3′-Dideoxycytidine Derivatives Containing a Small 5′-(0-Alkoxycarbon-ylphosphinyl) or 5′-(O-Cholesterylcarbonylphosphinyl) Substituent

Abstract

A convenient general method of synthesis of 5′-O-(alkoxycarbonyl)phosphonate esters of 2′,3′-dideoxyribonucleosides is presented, using the 5′-O-(methoxycarbonyl)phosphinyl, 5′-0-(ethoxycarbonyl)phosphinyl, and 5′-O-(cholesterylcarbonyl)phosphinyl derivatives of 3′-azido-3′-deoxythymidine (AZT) and the 5′-0-(ethoxycarbonyl)phosphinyl derivative of 2′,3′-dideoxycytidine (ddC) as examples. Reaction of trimethyl phosphonoformate, methyl phosphonoformate, or dimethyl cholesterylcarbonylphosphonate with phosphorus pentachloride in carbon tetrachloride, followed by direct condensation of the resulting phosphonyl chloride with the nucleoside, gave the fully esterified phosphonoformate derivatives, which on treatment with sodium iodide in tetrahydrofuran underwent selective cleavage of the P-OMe or P-OEt groups, leaving the carboxylate esters intact. The resulting products were converted from sodium salts to ammonium salts by ion-exchange chromatography.     

Resistance Profiles of (+) 2′-Deoxy-3′-oxa-4′-thiocytidine and (-) 2′-Deoxy-3′-oxa-4′-thio-5-fluorocytidine

Abstract

Resistant variants were selected in vitro against two novel nucleoside analogues, (+) dOTC and (-) dOTFC using the HIV-1 molecular clone HXB2D. The variants obtained displayed 6.5-fold and 10-fold resistance to these compounds, respectively. Cloning and sequencing of the RT genes of the selected viruses identified two mutations, M184I for (+) dOTC and M184V for (-) dOTFC. Results with mutated recombinant clones of HXB2D confirmed the importance of these mutations in MT-4 cells. The resistance profiles of clinical samples with wild-type or 3TC-resistant phenotypes were also studied; low to moderate levels of cross-resistance were observed against the novel compounds.     

Synthetic and Antiviral Studies of Certain Acyclic 3′-Azido-3′-Deoxythymidine (AZT) Analogues

Abstract

A direct alkylation of trimethylsilylated pyrimidines and azapyrimidines with 1-azido-3-benzyloxy-2-chloromethoxypropane gave acyclic analogues of AZT in a good overall yield. None of the compounds exhibited significant antiviral activity against human immunodeficiency virus and herpes simplex virus.     

SYNTHESIS OF 3′-THIOAMIDO-MODIFIED 3′-DEOXYTHYMIDINE-5′-TRIPHOSPHATES AND THEIR USE AS CHAIN TERMINATORS IN SANGER-DNA SEQUENCING

The thioamide derivatives 3′-deoxy-5′-O-(4,4′-dimethoxytrityl)-3′-[(2-methyl-1-thioxo-propyl)amino]thymidine 1 and 3′-deoxy-5′-O-(4,4′-dimethoxytrityl)-3′-{{6-{[(9H-(fluo-ren-9-ylmethoxy)carbonyl]-amino}-1-thioxohexyl}amino} thymidine 2 were synthesized by regioselective thionation of their corresponding amides 7 and 8 with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphet-ane-2,4-disulfide (Lawesson's reagent). The thioamides were converted into the corresponding 5′-triphosphates 3 and 4. Compound 3 was chosen for DNA sequencing experiments and 4 was further labelled with fluorescein.     

A NEW APPROACH TO THE SYNTHESIS OF 4′-CARBON-SUBSTITUTED NUCLEOSIDES: DEVELOPMENT OF A HIGHLY ACTIVE ANTI-HIV AGENT 2′, 3′-DIDEHYDRO-3′-DEOXY-4′-ETHYNYLTHYMIDINE

Oxidation of 3′-O-TBDMS-4′,5′-unsaturated thymidine 3 with dimethyldioxirane (DMDO) allowed the isolation of the epoxide 4. Upon reacting with organosilicon reagents in the presence of SnCl₄, 4 underwent stereoselective ring opening to give 4′-α-allyl (6), 4′-α-(2-bromoallyl) (7), 4′-α-(cyclopenten-3-yl) (8), and 4′-α-cyano (9) derivatives of thymidine. Reactions of the 3′-epimer 12 with organoaluminum reagents gave 4′-α-methyl (13), 4′-α-vinyl (14), and 4′-α-ethynyl (15) analogues. Compounds 13–15 were transformed into corresponding 2′,3′-didehydro-3′-deoxy derivatives. Evaluation of their ability to inhibit the replication of HIV in cell culture showed that 4′-ethynyl-d4T (19) is more potent and less toxic than the parent compound d4T.     

A Short Syhthesis of 3′-(Methylsulfinyl)-3′-Deoxythymidine and Related Analogues

Abstract

The ring opening of the O-2,3′-anhydrothymidine 5 with the anion of methyl mercaptan gave the 3′-methylthio derivaative 6. Subsequent oxidation and deprotection afforded 3′-(methyl-sulfinyl)-3′-deoxythymidine 2 and its sulfone analogue 3.     

Synthesis of Two 3-(7′-Theophyllyl)glycals, 3-Deoxy-3-(7′-theophyllyl)-d-xylo-hex-1-enopyranose and Methyl 3-Deoxy-3-(7′-theophyllyl)-d-xylo-hex-1-enopyranuronate,and their Derivatives

Two 3-(7′-theophyllyl)glycals, (IV) and (V), were synthesized by fusion of theophylline and the appropriate glycals in the presence of p-toluenesulfonic acid. The structure and stereochemistry of the glycals were determined mainly from NMR analysis of their dihydro and 1,6-anhydro derivatives.     

PREPARATION OF 3′-C-BRANCHED URIDINE ANALOGUES,SUITABLE FOR CONVERSION INTO FUNCTIONALISED 3′-C-METHYLENE DERIVATIVES

A novel method for preparation of 1-[2-O-(tert-butyldimethylsilyl)-3-deoxy-3-C-hydroxymethyl-5-O-monomethoxytrityl-β-D-ribo-pentofuranosyl]uracil by hydroboration of corresponding 3′-deoxy-3′-C-methyleneuridine derivative has been developed. Further conversion of the hydroxyl function into different leaving groups was carried out to afford derivatives suitable for conversion into various 3′-C-branched uridine analogues through substitution.