A divergent synthesis of d - and l -carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides as potential antiviral agents

Synthesis of Some Mono- and Disaccharide-Grafting Phthalazine Derivatives and Some New Se-Nucleoside Analogues: Antibacterial Properties, Quantum Chemical Calculations, and Cytotoxicity

A highly efficient and versatile synthetic approach for the synthesis of 4-(pyren-1-ylmethyl)-1-(d-glycosyloxy) phthalazine nucleosides 11a,b, 13, β-S-nucleosides 16, 18, 20, and acyclo C-nucleosides 23a,b, 24, 25 and 27a-f was described and fully characterized. Furthermore, a series of desired new nucleoside analogues containing Se of 4-(pyren-1-ylmethyl) phthalazine-1(2H)-selenone 28-33 were synthesized. The structures of all reported compounds were confirmed by IR, ¹H-NMR, ¹³C-NMR, MS and elemental analysis. All compounds have been screened for their antibacterial and antifungal activities. Maximum activity was shown by 20 and 33a comparable to the standard drugs with lower toxicity. The cytotoxicity of the selected compound was measured and evaluated. The energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital was calculated using theoretical computations to reflect the chemical reactivity and kinetic stability of the synthesized compounds. Using density functional theory (DFT), electronic parameters such as the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) and the molecular electrostatic potential (MEPS) were calculated. On the basis of different studied structures, these properties were computed in order to elucidate the chemical reactivity and the kinetic stability. Obviously, the band gap energy (Eg) of structures studied reveals that the lowest band gap obtained for the structure 16-a indicates that it has the highest chemical reactivity and lowest kinetic stability.

Recent Advances in the Synthesis of the Carbocyclic Nucleosides as Potential Antiviral Agents

Compared with 4′-oxonucleosides, there have been far fewer systematic structure-activity relationship studies on carbocyclic nucleosides as antiviral and antitumour agents. This is mainly because of the synthetic problems in preparing the carbasugars. However, the recent discovery of the ring-closing metathesis (RCM) (a powerful tool for the preparation of 5-membered carbasugar via C-C bond formation) has made it possible to synthesize the key carbasugars to a preparative scale. This review summarizes the asymmetric syntheses of carbasugars and carbocyclic nucleosides, using an RCM reaction as a key step. Furthermore, the review includes valuable information for designing and synthesizing novel carbocyclic nucleosides.

Synthesis and antiretroviral activity of novel 4'-fluoro-5'-deoxyphosphonic acid carbocyclic nucleoside analogs

Novel 5'-deoxycarbocyclic purine phosphonic acid analogs with the 4'-electropositive moiety, fluorine were designed, and synthesized from glyceraldehyde. The cyclopentenol intermediate, 9, was successfully synthesized by the ring-closing metathesis of divinyl 8. The condensation reaction of cyclopentanol 15 with purine bases under Mitsunobu conditions successfully afforded the desired phosphonate analogs. The synthesized nucleoside phosphonic acid analogs, 19, 22, 26, and 29, were subjected to antiviral screening against human immunodeficiency virus (HIV)-1. Guanine phosphonic acid analog 29 showed significant anti-HIV activity (EC50 = 10.3 μM).

Synthesis and antiviral evaluation of novel 2',2'-difluoro 5'-norcarbocyclic phosphonic acid nucleosides as antiviral agents

A very efficient synthetic route to novel 2',2'-difluoro 5'-norcarbocyclic phosphonic acid nucleosides from but-3-en-1-ol 5 is described. The discovery of 2'-fluorinated furanose nucleoside 1 as a potent anti-HIV-1 agent has led to the synthesis and biological evaluation of 2'-modified 5'-norversions of the carbocyclic phosphonate nucleosides. The synthesized nucleoside analogues 18, 19, 23a, 23b, and 24 were tested for anti-HIV activity as well as cytotoxicity. Adenine analogue 19 shows significant anti-HIV-1 activity (EC(50) = 13 μM).

A review of methods to synthesise 4′-substituted nucleosides

Modified nucleosides have received a great deal of attention from the scientific community, either for use as therapeutic agents, diagnostic tools, or as molecular probes.

Synthesis and evaluation of novel 6',6'-difluoro 5'-deoxycarbocyclic phosphonic acid nucleosides as antiviral agents

The authors describe highly efficient synthetic routes for the preparation of novel 6',6'-difluoro 5'-deoxycarbocyclic phosphonic acid nucleosides from 1,4-dihydroxy-2-butene. The discovery that the 6'-fluorinated carbocyclic nucleoside (2, EC₅₀ = 0.16 μM) is a potent anti-HSV-1 agent led to the syntheses and biological evaluations of 6'-modified 5'-deoxyversions of carbocyclic phosphonate nucleosides. The synthesized nucleoside analogues 15, 18, 22, and 25 were tested for anti-HIV activity and for cytotoxicity. However, none of them showed significant anti-HIV-1 activity or cytotoxicity at concentrations up to 100 μM.

Synthesis of novel 6'-spirocyclopropyl-5'-norcarbocyclic adenosine phosphonic Acid analogues as potent anti-hiv agents

Novel 5'-norcarbocyclic adenosine phosphonic acid analogues with 6'-electropositive moiety such as spirocyclopropane were designed and synthesized from the commercially available diethylmalonate 5. Regioselective Mitsunobu reaction proceeded in the presence of an allylic functional group at a low reaction temperature in polar cosolvent [dimethylformamide (DMF)/1,4-dioxane] to give purine analogue 15. To improve cellular permeability and enhance the anti-human immunodeficiency virus (HIV) activity of this phosphonic acid, a SATE phosphonodiester nucleoside prodrug 23 was prepared. The synthesized adenosine phosphonic acids analogues 18-21 and 23 were subjected to antiviral screening against HIV-1.

Design and synthesis of carbocyclic versions of furanoid nucleoside phosphonic Acid analogues as potential anti-hiv agents

Novel 5'-norcarbocyclic adenine and guanine phosphonic acid analogues with 6',6'-difluorine moiety were designed and synthesized from commercially available epichlorohydrin 5. A regioselective Mitsunobu reaction successfully proceeded from an allylic functional group 16b at low reaction temperature in polar cosolvent to give purine phosphonate analogues 17 and 24, respectively. The purine nucleoside phosphonate and phosphonic acid analogues were subjected to antiviral screening against HIV-1. Adenine analogue 21 and its SATE prodrug 29 show significant anti-HIV activity in MT-4 cell lines.

Synthesis of novel 4'-cyclopropyl-5'-norcarbocyclic adenosine phosphonic acid analogues

Novel 4'-cyclopropyl-5'-norcarbocyclic adenosine phosphonic acid analogues were designed and racemically synthesized from propionaldehyde 5 through a de novo acyclic stereoselective route using triple Grignard addition and ring-closing metathesis (RCM) as key reactions. To improve cellular permeability and enhance the anti-HIV activity of this phosphonic acid, SATE phosphonodiester nucleoside prodrug 23 was prepared. The synthesized adenosine phosphonic acids analogues 17, 18, 19, 21, and 23 were subjected to antiviral screening against HIV-1. Compound 23 exhibits enhanced anti-HIV activity than its parent nucleoside phosphonic acid 18.

A linchpin carbacyclization approach for the synthesis of carbanucleosides

A convenient synthesis of carbanucleosides, with both enantiomers equally accessible, is reported. The key step is a tandem linchpin cyclization process to give access to substituted carbafuranose derivatives having the correct relative stereochemistry for subsequent nucleobase introduction with inversion of configuration at C1. This was illustrated by the synthesis of 2',3'-dideoxycarbathymidine via a convergent nucleobase introduction and of 2',3'-dideoxy-6'-hydroxycarbauridine via a linear nucleobase introduction. Both methods relied on Mitsunobu chemistry, and the first example of the Mukaiyama modification of the Mitsunobu reaction involving nucleobases as nucleophiles is reported.

Synthesis of 4/5-Deoxy-4/5-nucleobase Derivatives of 3-O-Methyl-D-chiro-inositol as Potential Antiviral Agents

Using D-pinitol (= 3-O-methyl-D-chiro-inositol) as starting material, a concise synthesis of 4/5-deoxy-4/5-nucleobase derivatives 11-19 has been achieved. The key intermediate 9 was obtained in good yield via an epoxidation from mono-methanesulfonate of D-pinitol. The process of opening of the epoxide ring in 9 by nucleobases appeared to be regioselective in presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). All the synthesized carbocyclic nucleosides were assayed against several viruses and tumors such as HIV-1, HSV-1, and HSV-2, and lung and bladder cancer. However, only compounds 14b, 14a, 16a, 16b, and 19 showed mild inhibitory effect against human lung cancer cell lines (PG) with IC50 values ranging from 50 to 100 microM, and the other compounds did not exhibit any significant antiviral activity or cytotoxicity even at concentrations up to 200 microM.

Synthesis and biological evaluation of phosphonated dihydroisoxazole nucleosides

Phosphonated isoxazolinyl nucleosides have been prepared via 1,3-dipolar cycloaddition reaction of nitrile oxides with corresponding vinyl or allyl nucleobases for antiviral studies. The cytotoxicity, the anti-HSV activity and the RT-inhibitory activity of the obtained compounds were evaluated and compared with those of AZT and diethyl{(1'SR,4'RS)-1'-[[(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)]-3'-methyl-2'-oxa-3'-azacyclopent-4'-yl]}methylphosphonate, a saturated phosphonated dihydroisoxazole nucleoside analogue.

Synthesis of novel apio carbocyclic nucleoside analogues as selective a(3) adenosine receptor agonists

On the basis of the biological activity of neplanocin A and apio-dideoxyadenosine (apio-ddA), novel apio-neplanocin A analogues 5a-d, combining the properties of two nucleosides, were stereoselectively synthesized. The apio moiety of the target nucleosides 5a-d was stereoselectively introduced by treating lactol 10 with 37% formaldehyde in the presence of potassium carbonate. The carbasugar moiety of neplanocin A was successively built by exposing diene 12 on a Grubbs catalyst in methylene chloride. The final nucleosides 5a-d were synthesized from the condensation of the glycosyl donor 14 with nucleic bases under the standard Mitsunobu conditions. Similarly, apio-aristeromycin 6 and (N)-apio-methanocarbaadenosine 7 were derived from the common intermediate 13 using catalytic hydrogenation and Simmons-Smith cyclopropanation as key steps. All of the final nucleosides 5a-d, 6, and 7 did not show significant inhibitory activity against S-adenosylhomocysteine hydrolase (SAH) up to 100 muM, maybe due to the absence of the secondary hydroxyl group at the C3'-position, which should be oxidized by cofactor-bound NAD(+). However, apio-neplanocin A (5a) showed potent and highly selective binding affinity (K(i) = 628 +/- 69 nM) at the A(3) adenosine receptor without any binding affinity at the A(1) and A(2A) adenosine receptors. In conclusion, we have first developed novel carbocyclic nucleosides with unnatural apio-carbasugars using stereoselective hydroxymethylation and RCM reaction and also discovered a new template of human A(3) adenosine receptor agonist, which play a great role in developing new A(3) adenosine receptor agonist as well as in identifying the binding site of the receptor.

Solid phase synthesis of carbocyclic l-2'-deoxynucleosides

[reaction: see text] Carbocyclic L-2'deoxynucleosides 17 were synthesized on solid phase in four steps from the appropriately protected intermedate 11. The Mitsunobu reaction was used as a condensation method between the carbocyclic moiety and heterocyclic bases. The regioselectivity of the carbocyclic nucleosides was compared between the solid and solution phase syntheses.