3′-C-Trifluoromethyl Ribonucleosides

Deoxytrifluoromethylation of Alcohols

Deoxy-functionalization of alcohols represents a class of reactions that has had a profound impact on modern medicine. In particular, deoxyfluorination is commonly employed as a means to incorporate high-value fluorine atoms into drug-like molecules. Recently, the trifluoromethyl (CF₃) group has garnered attention from medicinal chemists due to its ability to markedly improve the pharmaceutical properties of small-molecule drug candidates. To date, however, there remains no general means to accomplish the analogous deoxygenative trifluoromethylation of alcohols. We report herein a copper metallaphotoredox-mediated direct deoxytrifluoromethylation, wherein alcohol substrates are activated in situ by benzoxazolium salts for C(sp³)-CF₃ bond formation.

Synthesis of 3′-β-carbamoylmethylcytidine (CAMC) and its derivatives as potential antitumor agents

3'-beta-Carbamoylmethylcytidine (CAMC) and its derivatives were synthesized using an intramolecular Reformatsky-type reaction promoted by SmI2 as the key step. In vitro tumor cell growth inhibitory activity was evaluated and CAMC was found to exhibit potent cytotoxicity against various human tumor cell lines. From a structure-activity relationship study it was postulated that the cytotoxic mechanism of action of CAMC did not require phosphorylation at the 5'-hydroxyl group. This study provides a novel strategy for the development of a new type of antitumor nucleoside.

Synthesis and studies of 3'-C-trifluoromethyl-beta-D-ribonucleosides bearing the five naturally occurring nucleic acid bases

3'-C-Trifloromethyl-beta-D-ribonucleoside derivatives bearing the five naturally occurring nucleic acid bases have been synthesized. All these derivatives were prepared by glycosylation reactions of purine and pyrimidine bases with a suitable peracylated 3-C-trifluoromethyl ribofuranose precursor. After deprotection, the resulting title nucleoside analogues were tested for their inhibitory properties against the replication of HIV, HBV and several RNA viruses. However, none of these compounds showed significant antiviral activity.

Phosphonyl, phosphonothioyl, phosphonodithioyl, and phosphonotrithioyl radicals: generation and study of their addition onto alkenes

The treatment of benzyl dialkyl phosphites and dithiophosphites with benzeneselanyl chloride generates an Arbuzov-type transformation leading to the dialkyl selenophosphates 19a and 19b and to selenophosphorodithioates 21a and 21b. Interaction of these substrates with Lawesson's reagent yields the corresponding selenophosphorothioates 20a and 20b and the selenophosphorotrithioates 22a and 22b. When treated with a radical initiator in the presence of a hydrogen donor and an alkene, all eight phosphorus(V) precursors undergo homolytic cleavage of the P-Se bond to generate the phosphonyl, phosphonothioyl, phosphonodithioyl, or phosphonotrithioyl radicals. Most of these are shown to add onto electron-rich and electron-poor alkenes to deliver the expected adducts in fair to excellent yields. Cyclic precursor 19b displays peculiar behavior and, under the reaction conditions, produces only the corresponding cyclic phosphite. Application of this radical chain process is carried out on furanosyl 3-exo-methylene derivative 37 to diastereoselectively furnish five new 3-phosphonomethyl-, 3-phosphonothiomethyl-, and 3-phosphonodithiomethyl-3-deoxofuranoses 38a-c and 38f,g. The possibility of conducting tandem processes is also discussed through experiments involving (1R)-(+)-alpha-pinene (39) and diallylamine 41.

Synthesis and hybridization properties of oligodeoxynucleotides containing 3'-deoxy-3'-C-methyleneuridine

3'-Deoxy-3'-C-methyleneuridine nucleoside 1 has been incorporated into oligodeoxynucleotides. Relative to the unmodified references, oligomers containing nucleoside 1 displayed reduced binding affinities towards complementary DNA and RNA with a tendency towards RNA-selective hybridization.

First and efficient synthesis of phosphonodifluoromethylene analogues of nucleoside 3'-phosphates: crucial role played by sulfur in construction of the target molecules

Phosphoric esters of secondary alcohols are ubiquitous in biological systems. However, despite the obvious interest of the corresponding difluoromethylene phosphonates as isopolar mimics, a single example of such an analogue featuring this particular substitution pattern has so far been reported in the literature, due to synthetic problems associated with their preparation. The lithium salt of diethyl difluoromethylphosphonothioate 28d provides a solution to this problem, as demonstrated by an 8-step synthesis of all five fully protected analogues of nucleoside 3'-phosphates in 9-18% overall yield, from readily available ketones. Sulfur is shown to play a crucial role in the introduction of the phosphorus-substituted difluoromethylene unit onto the furanose ring. Complete diastereoselectivity is observed in the three steps of the process requiring stereocontrol. The key conversion of the P=S bond into its oxygenated analogue is simply achieved by use of m-chloroperoxybenzoic acid. It is noteworthy that the synthesis can be carried out on large scale: a 31-g batch of compound 26b has been prepared. The deprotected nucleoside 3'-phosphate analogues can be liberated from their precursors as exemplified by the conversion of 7b, 8b, and 9b into the corresponding difluorophosphonic acids, isolated in the form of their disodium salts.

Synthesis of 2',3'-dideoxy-2'-trifluoromethylnucleosides from alpha-trifluoromethyl-alpha,beta-unsaturated ester

The treatment of alpha-bromo-alpha,beta-unsaturated esters 2 with FSO(2)CF(2)CO(2)Me and CuI in DMF/HMPA constitutes a new synthetic scheme for the preparation of alpha-trifluoromethyl-alpha, beta-unsaturated esters 3. The trifluoromethylation of (Z)/(E)-ethyl 3-[(S)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-bromo-2-propenoate (2e), which is derived from 1-(R)-glyceraldehyde acetonide, yields the key intermediate alpha-trifluoromethyl-alpha,beta-unsaturated esters 3e. This is transformed into anomeric acetates 8a and 8b and is used for the synthesis of a number of 2', 3'-dideoxy-2'-trifluoromethylnucleosides.

C-Difluoromethylene-containing, C-trifluoromethyl and C-perfluoroalkyl carbohydrates. Synthesis by carbohydrate transformation or building block methods

The synthetic methods for preparing carbohydrates bearing a C-branched substituent of the type CF2-Y, with Y = F, Y = CnF(2n + 1) or Y = a carbon-attached or heteroatom-attached nonfluorinated residues, are reviewed. Both direct introduction of C-branched fluorinated substituents (direct trifluoromethylation, perfluoroalkylation or difluoromethylenation) and building block methods from fluorinated synthons are considered.

Fluorinated nucleosides

The synthesis and biological activity of deoxyfluoro nucleosides are reviewed.

Synthesis of 3'-trifluoromethyl nucleosides as potential antiviral agents

1,2-Di-O-acetyl-3-deoxy-3-trifluoromethyl-5-O-benzoyl-beta-D-ribofuranos e was synthesized from the precursor keto sugar by the use of Ruppert's reagent (CF3SiMe3) as the source of a nucleophilic trifluoromethyl group. Coupling of this trifluoromethyl sugar with nucleobases and elaboration gave novel deoxy and dideoxynucleosides. A single crystal X-ray analysis confirmed the structure and stereochemistry. The deoxynucleosides were converted through an elimination reaction to their dideoxydidehydro derivatives.

Homologues of isomeric dideoxynucleosides as potential antiviral agents: synthesis of isodideoxynucleosides with a furanethanol sugar moiety

The synthesis of a homologues series of compounds related to (R, S)-isodideoxynucleosides has been completed by coupling a variety of natural purine and pyrimidine bases with a modified sugar intermediate. This sugar precursor was prepared regiospecifically and stereospecifically from D-glucose.

Synthesis of 3-C-(methyl beta-D-xylofuranosid-3-yl)-5-phenyl-1,2,4-oxadiazole

Nucleophilic addition of KCN to 5-O-benzoyl-1,2-O-isopropylidene-alpha-D-erythro-pentofuranos-3-++ +ulose gave the xylo cyanohydrin stereoselectively. Several xylos-3-yl-1,2,4-oxadiazole derivatives were synthesized from this cyanohydrin and were converted into 3-C-(methyl beta-D-xylofuranosid-3-yl)-5-phenyl-1,2,4-oxadiazole.