Synthesis of 9-(2-Deoxy-2-Fukuoro-β-D- Abinoruranosyl)Hypoxhine. The First Direct Introduction of A 2′-β-Fldoro Substituent in Ppepormed Purine Nucleosides. Studies Directed Toward the Synthesis of 2′-DEOXY-2′-Substituted Arabppmocebosides. 8.1

Abstract

The 3′, 5′-di-O-acetyl-, 3′-, 5′-di-O-balzyl-, 3′-O-acety -5-O-trityl- and 3′-, 5′ -di-O-trityl-2′-O-triflyl-1-benzylhnosine (8c, 15, 20C, and 27, respectively) were prepared and subjected to nucleophilic reaction with TASF. Thus, 3′, 5′-O-(1, 1, 3, 3-tetraisopropyldisiloxanyl)-1-benzylinosine (5c) was triflylated, desilylated, and then acetylated to give 8c. Also, 5c was converted into the 2′-O-tetrahydropyrnyl (W) derivative 11 which was desilylated and then benzylated to give 2′-O-tetrahydropyranyl-O^3′, O^5′, N¹-tribenzylinosine (13). Removal of the THP group from 13 followed by triflylation afforded 2′-O-triflyld-O^3′,O^5′ N¹-tribenzylinosine (15). 3′-O-Acetyl-2′ -O-triflyl-,O^5′,N¹-inosine (20) was prepared frmn 5′ -O-trityl-1-benzylhh (18c) by conversion into the 2′-, 3′-O-(di-n-butylstannylene) derivative which was treated with triflyl chloride and then acetylated. Treatment of 1-benzyl-inosine (4c) with trityl chloride in pyridine containing p-dimethylamino-pyridine afforded a mixture of 2′-, 5′- and 3′-, 5′-di-O-trityl-l-benzylinosine (25 and 26, respectively). These regioiscums were chrcanato-graphically separated. Triflylation of 26 gave 2′-o-triflyl-3′-, 5′-di-O-trityl-1-benzylhoshe (27).

The triflates 8c and 15 only afforded elhination products upon treatment with TASF. However, the trif late group in 20c and 27 was displaced by fluoride with fornation of the 2′-fluoro-arabino nucleosides, 21c and 28, in 10 and 30% yield, respectively. After deprotection of 28, 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)hypowntkine (1, F-ara-H) was obtained in good yield. The conformational influence of the sugar protecting groups on the rate of nucleophilic substitution against elimination is discussed.     

The Synthesis of Some 5-Alkyl (Cycloalkyl)-Substituted 2′ -Deoxy-4′-Thiouridines

Abstract

The silylated pyrimidine bases IIa-d were condensed with the benzyl 3,5-di-O-benzyl-2-deoxy-1,4-dithio-d-erythro-pentofuranoside III in acetonitrile under activation by N-iodosuccinimide, giving ca 1.5: 1/α: β anomeric mixtures of the blocked nucleosides IVa-d and Va-d. in yields of 55–58%. After the separation on a silica column the pure anomers were deprotected by BCI₃ or TiCI₄, providing the free nucleosides VIa-d and VIIa,c,d in moderate to good overall yields. The β- or α-anomeric configuration, anti-glycosidic conformation and prevailing C2′endo(S) thiosugar pucker in the synthesized compounds were established by the combined use of the ¹H, ¹³C NMR and X-ray crystallography.

     

Synthesis and Some Properties of Modified Oligonucleotides. II. Oligonucleotides Containing 2′-Deoxy-2′-fluoro-β-D-arabinofuranosyl Pyrimidine Nucleosides

Abstract

In order to find the effects of unnatural nucleosides on the stability of duplex, several oligonucleotides containing 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-uracil(FAU),-cytosine (FAC) and -thymine (FMAU) were synthesized by two alternative approaches: phosphoramidite method on an ABI 392 synthesizer and H-phosphonate procedure on our GeneSyn I universal module synthesizer. It was shown from the melting profiles that the presence of FMAU has a large stabilizing effect on the duplex. Replacement of thymidine with FAU, or deoxycytidine with FAC resulted in the formation of less stable duplexes. Temperature-dependent CD spectroscopy demonstrated that the structures of the fluorine containing oligomers are very similar to those of unmodified oligomers.     

Conformationally Locked Nucleoside Analogs. Synthesis of 2′-Deoxy-2′-C, 4′-C-Bridged Bicyclic Nucleosides

Abstract

1-α-Methylarabinose was converted, in three steps, to 2-deoxy-2-methyleneribose derivative 3, which was subjected to hydroboration to give 2-α-hydroxymethyl derivative 4 exclusively. 4 was converted to 2,4-bis(hydroxymethyl)ribose derivative 6 in four steps. Mesylation, detritylation, and ring closure, followed by hydrolysis of the mesyl group at O5, gave 3,6-dioxabicyclo[3,2,1]octane derivative 8. After acetylation, 8 was coupled with silylated 6-chloropurine to give desired α- and β-bicyclic-sugar nucleosides.     

Synthesis of 2′-Deoxy-6,2′-Ethano-Cyclouridine1 (Nucleosides and Nucleotides. Part 57)

Abstract

Synthesis of a carbon-bridged cyclouridine,2′-deoxy-6,2′-ethano-cyclouridine, was accomplished starting from a 2′-ketouridine via the 2′-deoxy-2′-iodoethyl-5-chlorouridine derivative through a radical cyclization.     

Synthesis and Incorporation of 5″-Amino- and 5′-Mercapto-5′-Deoxy-2′-O-Methyl Nucleosides Into Hammerhead Ribozymes

Abstract

Novel 5′-amino-5′-deoxy-2′-O-methyl uridine, guanosine and adenosine 3′-O-phosphoramidites 5, 11, and 20, as well as protected 5′-mercapto-5′-deoxy-2′-O-methyl uridine 3′-O-phosphoramidite 23 were synthesized from 2′-O-methyl nucleosides. These analogs were incorporated at the 5′-ends of hammerhead ribozymes to evaluate achiral bridging 5′-N- phosphoramidates and 5′-S-phosphorothioates as alternatives for non- bridging phosphorothioates commonly used for end stabilization against nucleases. Oligonucleotide synthesis and deprotection conditions were optimized for better yields of these modified ribozymes.     

Nucleosides. 140. Stereoselectivity of the Reaction of 1-(2,3-Anhydro-5-O-Benzoyl-β-D-Lyxofuranosyl) Uracil with Ammonium Azide. Isolation and Characterization of 2-Azido-Xylo-Nucleoside Derivatives

Abstract

The composition of the products of reaction of 1-(2,3-anhydro-5-O-benzoyl-β-D-lyxofuranosyl)uracil (1) with NH₄N₃ was studied by a reverse-phase HPLC system which was found to separate the 3-azido-arabino 2 and 2-azido-xylo 3 isomers that were formed. The use of a 10:1 ratio of NH ₄ N ₃ to 1 in refluxing EtOH was found to minimize ring opening at C-2 (7%). The higher stereoselectivity of ring opening produced by using a large excess of NH ₄ N ₃ was suppressed by conducting the reaction in DMF. Preventing the escape of the NH ₃ by-product only resulted in debenzoylation. The isolation of pure, crystalline 3 was achieved by reverse-phase preparative HPLC. Separation from the arabino isomer was also effected by debenzoylation and selective acetonide formation with the xylo isomer, which allowed facile isolation of the latter by normal phase chromatography. Hydrolysis of the acetonide 7 provided unprotected 2-azido-xylo nucleoside 6, which was also obtained by NaOMe treatment of 3. The mechanistic basis for the stereoselectivity of epoxide opening is discussed.     

Nucleosides. 140. Stereoselectivity of the Reaction of 1-(2,3-Anhydro-5-O-Benzoyl-β-D-Lyxofuranosyl)Uracil with Ammonium Azide. Isolation and Characterization of 2-Azido-XYLO-Nucleoside Derivatives.1

Abstract

The composition of the products of reaction of 1-(2,3-anhydro-5-O-benzoyl-β-D-lyxofuranosyl)uracil (1) with NH₄N₃ was studied by a reverse-phase HPLC system which was found to separate the 3-azido-arabino 2 and 2-azido-xylo 3 isomers that were formed. The use of a 10:1 ratio of NH₄N₃ to 1 in refluxing EtOH was found to minimize ring opening at C-2 (7%). The higher stereoselectivity of ring opening produced by using a large excess of NH₄N₃ was suppressed by conducting the reaction in DMF. Preventing the escape of the NH₃ by-product only resulted in debenzoylation. The isolation of pure, crystalline 3 was achieved by reverse-phase preparative HPLC. Separation from the arabino isomer was also effected by debenzoylation and selective acetonide formation with the xylo isomer, which allowed facile isolation of the latter by normal phase chromatography. Hydrolysis of the acetonide 7 provided unprotected 2-azido-xylo nucleoside 6, which was also obtained by NaOMe treatment of 3. The mechanistic basis for the stereo-selectivity of epoxide opening is discussed.     

A Direct and Efficient Synthesis of 5′-Deoxy-2′, 3′-

Abstract

A direct and efficient synthesis of 5′-deoxy-2′,3′-O-isopropylideneinosine, 7, from readily available inosine is described. An example of a potentially general synthesis of N -substituted-5′-deoxyadenosines from 7 is also described.     

The Synthesis of Novel Carbohydrates Amenable to the Synthesis of 2′,3′-Dideoxy-3′-Branched Nucleosides

Abstract

The facile synthesis of several substituted carbohydrates that are amenable for the preparation of 2′,3′-dideoxy-3′-hydroxymethyl nucleosides are reported. Elaboration of a previously reported analog, 5-O-benzoyl-3-deoxy-3-(benzyloxy)methyl-1,2-O-isopropylidene-β-D- ribofuranose (4) has provided two 2,3-dideoxy-3-branched ribose derivatives 5-O-benzoyl-2,3-dideoxy-3-(benzyloxy)methyl-1-O-methyl-β-D-ribofuranose (7) and 1.5-di-O-benzoyl-2,3-dideoxy-3-(benzyloxy)methyl-(α,β)-D-ribofuranose (10). Due to problems involved with the separation of anomeric mixtures when these carbohydrates were condensed with an heterocycle, another versatile synthon 5-O-benzoyl-3-deoxy-3-(benzyloxy)methyl-2-O-t-butyldimethylslyl-1-O- methyl-β-D-ribofuranose (12) was synthesized. The utility of this compound (12) is demonstrated in the total synthesis of 1-[3-deoxy-3-hydroxymethyl-β-D-ribofuranosyl]thymine (20).     

Synthesis and Structure Activity Relationships of 5-Substituted - 4′-thio-β-D-Arabinofuranosylcytosines

Abstract

Four 5-substituted (chloro, fluoro, bromo, methyl) 1-(4-thio-P-Darabinofuranosy1) cytosines and their a anomers were synthesized by a facile route in high yields. All of these nucleosides were evaluated for cytotoxicity against a panel of human tumor cell lines in vitro. Only 5-fluoro-1 -(4-thio-β-D-arabinofuranosyl)cytosine was found to be highly cytotoxic in all the cell lines and was further evaluated in vivo.     

Systematic Synthesis and Antiviral Evaluation of α-L-Arabinofuranosyl and 2′-Deoxy-α-L-Erythro-Pento-Furanosyl Nucleosides of the Five Naturally Occurring Nucleic Acid Bases

Abstract

The α-L-arabinofuranosyl and 2′-deoxy-α-L-erythro-pentofuranosyl analogues of the naturally occurring nucleosides have been synthesized and their antiviral properties examined. The α-L-arabinofuranosyl nucleosides were prepared by glycosylation of purine and pyrimidine aglycons with a suitably peracyl-α-L-arabinose, followed by removal of the protecting groups. Their 2′-deoxy derivatives were obtained by sequential selective 2′-O-deacylation and deoxygenation. All the prepared compounds were tested for their activity against a variety of RNA and DNA viruses, but they did not show significant antiviral activity.     

Nucleosides and Nucleotides. 139. Stereoselective Synthesis of (2′S)-2′-C-Alkyl-2′-deoxyuridines

Abstract

A synthetic method for (2′S)-2′-C-alkyl-2′-deoxyuridines (9) has been described. Catalytic hydrogenation of 1-[2-C-alkynyl-2-O-methoxalyl-3,5-O-TIPDS-β-D-arabino-pentofuranosyl]uracils (5) gave 1-[2-C-(2-alkyl)-2-O-methoxalyl-3,5-O-TIPDS-β-D-arabino-pentofuranosyl]uracils (4) as a major product, which were then subjected to the radical deoxygenation, affording (2′S)-2′-alkyl-2′-deoxy-3′,5′-O-TIPDS-uridines (7) along with a small amount of their 2′R epimers.

     

Synthesis and Antiviral Activities of 5-Substituted 1-(2-Deoxy-2-C-methylene-4-thio-β-D-erythro-pentofuranosyl)uracilst†

Abstract

Various 5-substituted 1-(2-deoxy-2-C-methylene-4-thio-β-D-erythropentofuranosyl)uracils (4′-thioDMDUs) were synthesized from D-glucose via sila-Pummerer-type glycosylation. All of the β-anomers of 5-substituted 4′-thioDMDU, except the 5-hydroxyethyl derivative, showed potent anti-HSV-1 activity (ED₅₀ = 0.016–0.096 μg/mL). 5-Ethyl- and 5-iodo-4′-thioDMDUs were also active against HSV-2 (ED₅₀ = 0.17 and 0.86 μg/mL, respectively). 5-Bromovinyl-4′-thioDMDU was particularly active against VZV (ED₅₀ = 0.013 μg/mL).

     

Synthetic Nucleosides and Nucleotides. XX1. Synthesis of Various 1-β-D-Xylofuranosyl-5-Alkyluracils and Related Nucleosides

Abstract

Treatment of D-xylose (1) with 0.5% methanolic hydrogen chloride under controlled conditions followed by benzoylation and acetolysis afforded crystalline 1-O-acetyl-2, 3, 5-tri-O-benzoyl-α-D-xylofuranose (4) in good yield. Coupling of 4 with 2, 4-bis-trimethylsilyl derivatives of 5-alkyluracils (methyl, ethyl, propyl and butyl) (5a-5d), 5-fluorouracil (5e) and uracil (5f) in acetonitrile in the presence of stannic chloride gave 1-(2,3,5-tri-O-benzoyl-β-D-xylofuranosyl)-nucleosides (6a-6f). Saponification of 6 with sodium methoxide afforded 1-β-D-xylofuranosyl-5-substituted uracils (7a-7f). Condensation of 4 with free adenine in similar fashion and deblocking gave carcinostatic 9-β-D-xylofuranosyladenine (7g).     

Nucleosides and Nucleotides. 232. Synthesis of 2′-C-Methyl-4′-thiocytidine: Unexpected Anomerization of the 2′-Keto-4′-thionucleoside Precursor

The synthesis of 2′-C-methyl-4′-thiocytidine (16) is described. Since the 2′-keto-4′-thiocytidine derivative 2β unexpectedly isomerized to 2α and the methylation of 2β proceeded predominantly from the less hindered α-face to give 7, the desired product 16 was synthesized via the Pummerer reaction of the sulfoxide 14 and N ⁴ -benzoylcytosine.     

Nucleosides. Part 3.1 Synthesis of 2-N-Substituted 1-β-D-Arabinofuranosylisocytosine Derivatives by The Reaction of 2′,5′-Dichloro-2′,5′-Dideoxyuridine with Amines

Abstract

Reaction of 2′,5′-dichloro-2′,5′-dideoxyuridine (1) with ammonia and benzylamine afforded the corresponding 2-N-substituted 1-(5-chloro-5-deoxy-β-D-arabinofuranosyl)-isocytosine derivatives (2 and 10). Reaction of 1 with ammonia, methylamine, cyclohexylamine, and benzylamine followed by treatment with methanolic sodium methoxide gave the corresponding 2-N-substituted 1-(2,5-anhydro-β-D-arabino-furanosyl)isocytosine derivatives (6, 11, and 12).     

Synthesis and Physicochemical Properties of 2′-Deoxy- 2′,2″-difluoro-β-D-ribofuranosyl and 2′-Deoxy-2′,2″- difluoro-α-D-ribofuranosyl Oligonucleotides

Abstract

We present procedures for nucleoside and oligonucleotide synthesis, binding affinity (T _m) and structural analysis (CD spectra) of 2′-deoxy-2′,2″-difluoro-α-D-ribofuranosyl and 2′-deoxy-2′,2″-difluoro-β-D-ribofuranosyl oligothymidylates. Possible reasons for the thermal instability of duplexes formed between these compounds and RNA or DNA targets are discussed.     

Derivatives of 1-(2-Deoxy-2-fluoro-β-D-arabinofuranosyl)-5-phenyluracil and 5-Benzyluracil. Synthesis and Biological Properties

Abstract

A number of 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)uracil and -cytosine nucleosides substituted at the 5 position with a nitrophenyl or nitrobenzyl group were synthesized from 5-phenyl- and 5-benzyluracil via condensation of the fluorinated sugar, followed by nitration. The corresponding amino analogues were also prepared by reduction of the nitro nucleosides. The uracil nucleosides were converted into the corresponding cytosine nucleosides by way of the triazole intermediates. None of these nucleosides exhibited significant activity against herpes simplex virus type 1 in Vero cells. However, cytosine nucleosides containing the o-nitrophenyl, p-nitrophenyl, p-nitrobenzyl or p-aminobenzyl substituent were found to be toxic (even at 1 μM) to uninfected Vero cells, although they were essentially nontoxic in HL-60 cells. The 5′-monophosphates of the uracil nucleosides were inhibitors of the reaction catalyzed by purified Ehrlich ascites carcinoma thymidylate synthase, the 5-phenyluracil nucleotides causing a strong inhibition, competitive vs dUMP, described by the K_i value of 0.01 μM.     

Synthesis and Anticancer Activity of 3-(3-Oxoprop-1-enyl)-Substituted Analogues of Carbocyclic Pyrimidine Nucleosides and 2′,3′-Dideoxy Pyrimidine Nucleosides

Abstract

Various 2′, 3′ -dideoxy and carbocyclic pyrimidine nucleosides, and their corresponding 3-(3-oxoprop-1-enyl) derivatives, have been synthesized and evaluated against murine L1210 and P388 leukemias and Sarcoma 180 and human CCRF-CEM lymphoblastic leukemia. Among the compounds tested, 3-(3-oxoprop-1-enyl)-3′ -fluoro-3′ -deoxythymidine (17), 3-(3-oxoprop-1-enyl)-3′ -azido-3′ -deoxythymidine (15) and 3-(3-oxoprop-1-eny!)-(+)-1-[(lα, 3β, 4α)-3-hydroxy-4-(hydroxymethyl)cyclopentyl]-5-methyl-2,4 (lH,3H)pyrimidinedione (6) were found to be the most active with ED₅₀, values of 0.5,0.2,0.1, and 0.3 μM; 1.2, 0.5,1.0 and 1.0 μM; and 0.8,0.7,1.5, and 3.0μM, respectively. Our preliminary findings indicate that the 3-(3-oxoprop-1-enyl) derivative of carbocyclic thymidine is approximately 7 times more active than the 3-(3-oxoprop-1-enyl) derivative of carbocyclic thymine riboside against L1210 leukemia cells in vitro, with ED₅₀ values of 0.8 μM and 5.5 μM, respectively. These findings suggest that the cytotoxicity of these compounds not only is dependent upon the 3-(3-oxoprop-1-enyl)-substituted group, but also may vary with the sugar moiety.