The Synthesis of 2-Fluoropurine Nucleosides

Abstract

2-Aminoadenosine, obtained by silylation-amination from guanosine, is readily converted by KNO₂/ HF/Pyridine in up to 80% yield into 2-fluoradenosine, which is a convenient starting material for the preparation of 9(β-D-arabinofuranosyl)-2-fluoroadenine 5′-phosphate (Fludara). N⁶N⁶-Pentamethylene-2-aminoadenosine and guanosine afford likewise the corresponding 2-fluoropurine nucleosides in high yields.     

Utilization of tetrabutylammonium triphenyldifluorosilicate (TBAT) in the synthesis of 6-fluoropurine nucleosides

Tetrabutylammonium triphenydifluorosilicate (TBAT) has been found to be a useful reagent for the conversion of 6-chloropurine nucleosides to 6-fluoropurine derivatives. The 6-chloropurine nucleosides were reacted with trimethylamine to form quaternary trimethylammonium salts which were treated in situ with TBAT in DMF to effect conversion to the 6-fluoro derivatives in yields of 59-72%.     

Synthesis Of 2,2,3-Tris(Hydroxymethyl)Methylenecyclopropane Analogues Of Nucleosides

Synthesis of 2,2,3-tris(hydroxymethyl)methylenecyclopropane analogues 16a, 16b, 17a, and 17b is described. Diethyl ester of Feist's acid 18b was hydroxymethylated via carbanion formation using formaldehyde under simultaneous isomerization to cis diester to give intermediate 19. Reduction followed by acetylation gave triacetate 22. Addition of bromine afforded reagent 23, which was used for alkylation-elimination of adenine and 2-amino-6-chloropurine to provide Z,E-isomeric mixtures of 24a and 24b. Deacetylation and separation furnished the Z-isomers 16a, 16c and E-isomers 17a, 17c. Hydrolytic dechlorination of 16c and 17c gave guanine analogues 16b and 17b. None of the analogues exhibited a significant antiviral activity. Adenosine deaminase is refractory toward adenine analogues 16a and 17a.     

Synthesis of Tubercidin, 6-Chlorotubercidin and Related Nucleosides

Abstract

Tubercidin (7-deazaadenosine, 1a) and several 6-chlorotuber-cidin derivatives were synthesized including 4-amino-6-chloro-7-β-D-ribofuranosylpyrrolo[2,3-d]pyrimidine-3′,5′-cycyclic phosphate 9. Isolation of a side product found in the glycosylation step of the reaction sequence proved to be the N-1 ribosyl-attached isomer as shown by X-ray diffraction analysis. All derivatives were tested for in vitro antiviral and antitumor activity.     

Selective Synthesis and Application to the Synthesis of (E)-Fluorovinyl Nucleosides

A selective method for synthesizing (E)-fluorovinyl was developed. Novel acyclic (E)-fluorovinyl versions of neplanocin A were designed and selectively synthesized as potential antiviral agents. The condensation of the bromide 7 with the nucleosidic bases (5-FU, C, A, G) and the deprotection afforded the desired acyclic fluorovinyl nucleosides. The synthesized compounds 11, 12, 13, and 16 were evaluated for their antiviral activity. The guanine derivative 16 showed toxicity-dependent anti-HIV-1 activity in MT-4 cells.     

Selective Metalation of 6-Methylpurines: Synthesis of 6-Fluoromethylpurines and Related Nucleosides

Abstract

A selective metalation at the 6-CH3 over C-8 of 6-methylpurine derivative 6 was observed with softer counter cation (Na⁺ or K⁺) of the base, while the harder Li⁺ showed no selectivity. In the presence of N-fluorobenzenesulfonamide (NFSI), this property was utilized for the synthesis of 6-fluoromethylpurine derivatives 4 and 5 as potential toxins for suicide gene therapy.     

Synthesis and Reactions of Some Glycosylamine Derivatives of 6-Azauracil Nucleosides

Abstract

Reaction of the silylated 6-azauracil (2) with 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-D-glucose (3) gave 1-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-ß-D-glucopyranosyl)-6-azauracil (4), which gave the free nucleoside 5 on deblocking. Acetalation of 5 gave the monoacetal 6 which was oxidized into the ketone 7. Reduction of 7 gave the allo-nucleoside 9 which on hydrolysis afforded the free nucleoside 10. Alternatively, compound 10 was obtained from mesylation of 6 to give 8 followed by subsequent acetolysis and hydrolysis.     

Synthesis of D-Fructofuranosylpurine Nucleosides

Abstract

The Mitsunobu reaction has been applied to the formation of purine nucleosides of D-fructofuranose. The use of O-benzyl protection results in a predominance of the β-configuration in these novel compounds and both α- and β-D-fructofuranosyladenine are obtained in stereochemically pure form.     

Synthesis of Cyclobutane Nucleosides

2-(6-Chloropurinyl)-3-benzoyloxymethylcyclobutanone can be prepared by reaction of 6-chloropurine with 3-benzoyloxymethyl-2-bromocyclobutanone. The N-alkylation gave both N-9 and N-7 regioisomers. Both regioisomers upon hydride reduction followed by aminolysis gave the corresponding adenine nucleoside analogues. However, the N-7 series led to the hypoxanthine analogues as byproducts.     

Imidazole Nucleosides IV Nucleosides of 5 (4)-Formamido-imidazole-4 (5)carboxamide

Abstract

Nucleosides of 5(4)-aminoimidazole-4(5)-carboxamide were formylated with sodium formate, formic acid and acetic anhydride to the β-D-ribo-, α-D-arabino-, α-L-arabino- and β-D-xylofuranosides of 5-formamidoimidazole-4-carboxamide, and to the β-D-ribo-, β-D-arabi-no-, α-D-arabino- and α-L-arabinopyranosides of 4-formamidoimidazole-5-carboxamide.     

Synthesis of 2′-Deoxypyrimidine Nucleosides via Copper (I) Iodide Catalysis

Abstract

The coupling of various 5-substituted-2,4- disilyl pyrimidines with ã–2-deoxy-3,5-di-p-toluyl ribofuransyl chloride in the presence of copper (I) iodide in chloroform yields predominantly β-nucleosides (>15/1 β/α selectivity in some cases) in >90% overall yields.     

The Synthesis of Novel 5-Trifluoroethoxy Pyrimidine Nucleosides

Abstract

The syntheses of 5-(2, 2, 2-trifluoroethoxy)uracil, 5-(2, 2, 2-trifluoroethoxy)arabinouridine and 5-(2, 2, 2-trifluoroethoxy) uridine are described.     

Synthesis of Some Quinolinium Nucleosides

Abstract

The preparation of a series of quinolinium nucleosides with substituents on the 3-, 4- and 6-position is described.     

Synthesis of Non-Natural Pyrimidine Nucleosides

Abstract

Two new non-natural nucleosides bearing an amide (8) or an amidine (9) function have been synthesized. Their properties and the geometry of the exocyclic double bond have been studied.     

Screening of Catalytically Active Microorganisms for the Synthesis of 6-Modified Purine Nucleosides

Modified nucleosides can be prepared by microbial transglycosylation from cheaper nucleoside precursors using free or immobilised whole cells. An efficient screening method to find transglycosylation activity in␣microorganisms was developed for the synthesis of 6-modified purine nucleosides, such as 6-chloro-, 6-methoxy-, 6-iodo- and 6-mercaptopurine ribonucleoside. Out of 100 microorganisms screened, Bacillus stearothermophilus ATCC 12980 was the best for this purpose.     

The Latest Progress in the Synthesis of Carbocyclic Nucleosides

Abstract

This review presents the latest developments in the field of carba-nucleosides (1994–1998). Special attention is paid to the synthesis of key precursors to those carba-nucleosides that possess significant biological activities or have novel structures.     

Terminal Fluoroolefins. The Synthesis of Novel Carboacyclic Nucleosides

Abstract

A facile preparation of ketone 7 from butanetriol acetonide 5 is reported, and its utility for the synthesis of novel carboacyclic nucleosides 3E, 3Z, 4E and 4Z by the selective manipulation of multiple functionalities is demonstrated.     

Synthesis of Nucleosides with Additional Nucleobases

The syntheses of two nucleosides with additional nucleobases in the 2′-position are presented. The nucleosides have two- and one-carbon linkers to the additional nucleobase, respectively. The two nucleosides are synthesized from different strategies. The nucleoside with two carbons in the linker has been incorporated into oligonucleotides and showed stabilization of a tree-way junction.     

Nucleosides,XLIII1) Synthesis and Properties of 04-Alkylthymidines

Abstract

Various 0⁴-alkylthymidines 14–20 have been synthesized by two different methods. 0⁴-Alkylation takes place with 3′,5′-di-0-acetyl- (2) and 3′,5′-di-0-benzoylthymidine (3) respectively in a silver ion catalysed reaction with alkyl halides, whereas the azolide approach makes use of a nucleophilic displacement of the appropriate intermediate by alkoxides and subsequent deacylation to the free nucleosides. Structural proofs are based on elemental analyses, UV- and ¹H-NMR-spectra.