Discovery of Imidazoquinolines with Toll-Like Receptor 7/8 Independent Cytokine Induction.

Toll-like receptors (TLRs) are key targets in the design of immunomodulating agents for use as vaccine adjuvants and anticancer treatments. The imidazoquinolines, imiquimod and resiquimod, have been shown to activate TLR-7 and -8 which in turn induce cytokine production as part of the innate immune response. Herein, we report the synthesis and discovery of a C7-methoxycarbonyl derivative of imiquimod that stimulates cytokine production but is devoid of TLR-7/8 activity.

DNA with branched internal side chains: synthesis of 5-tripropargylamine-dU and conjugation by an azide-alkyne double click reaction.

5-Tripropargylamine-2'-deoxyuridine (1 a) containing two terminal triple bonds was synthesized by a Pd-assisted Sonogashira cross-coupling reaction and was subsequently converted into the corresponding phosphoramidite building block (9) and employed in solid-phase oligonucleotide synthesis. T(m) experiments demonstrate that the presence of covalently attached branched tripropargylamine residues has a positive effect on the base pair stability. The two terminal C[triple chemical bond]C bonds of modified DNA were functionalized by means of Cu(I)-mediated 1,3-dipolar cycloaddition reactions (click chemistry) with azides such as 3-azido-7-hydroxycoumarin or 3'-azido-3'-deoxythymidine (AZT) both in solution and on solid support.

Nucleosides and oligonucleotides containing 1,2,3-triazole residues with nucleobase tethers: synthesis via the azide-alkyne 'click' reaction.

A series of novel 1,2,3-triazole nucleosides linked to DNA nucleobases were prepared via copper(I)-catalyzed 1,3-dipolar cycloaddition of N-9 propargylpurines or N-1 propargylpyrimidines with the tolouyl protected 1-azido-2-deoxyribofuranose 2 followed by treatment with NaOMe/MeOH or aq NH3. The antiviral activity of such compounds against selected RNA viruses is reported. The strongly fluorescent 1,2,3-triazole compounds 16 and 17 were synthesized from propargylated uracil 1a and propargylated adenine 1c with coumarin azide 15, and the fluorescence properties were studied.

6-Azauracil or 8-aza-7-deazaadenine nucleosides and oligonucleotides: the effect of 2'-fluoro substituents and nucleobase nitrogens on conformation and base pairing.

The stereoselective syntheses of 6-azauracil- and 8-aza-7-deazaadenine 2'-deoxy-2'-fluoro-beta-d-arabinofuranosides and employing nucleobase anion glycosylation with 3,5-di-O-benzoyl-2-deoxy-2-fluoro-alpha-d-arabinofuranosyl bromide as the sugar component are described; the 6-azauracil 2'-deoxy-2'-fluoro-beta-d-ribofuranoside was prepared from 6-azauridine via the 2,2'-anhydro intermediate and transformation of the sugar with DAST. Compounds show a preferred N-conformer population (100% N for , and 78% N for ) being rather different from nucleosides not containing the combination of a fluorine atom at the 2'-position and a nitrogen next to the glycosylation site. Oligonucleotides incorporating and were synthesized using the phosphoramidites and .

Fluorinated 7-deazapurine 2'-deoxyribonucleosides: modification at the nucleobase and the sugar moiety.

7-Deaza-7-fluoro-purine 2'-deoxynucleosides as well as 2'-deoxy-2'-fluoroarabinofuranosyl nucleosides 1-8 were synthesized. The fluorine atom was introduced on the base level with Selectfluor. Nucleobase-anion glycosylation was then employed to form the nucleosides.

Modification of DNA with octadiynyl side chains: synthesis, base pairing, and formation of fluorescent coumarin dye conjugates of four nucleobases by the alkyne--azide "click" reaction.

Oligonucleotides incorporating 5-(octa-1,7-diynyl)-2'-deoxycytidine 1a, 5-(octa-1,7-diynyl)-2'-deoxyuridine 2a and 7-deaza-7-(octa-1,7-diynyl)-2'-deoxyguanosine 3a, 7-deaza-7-(octa-1,7-diynyl)-2'-deoxyadenosine 4a were prepared. For this, the phosphoramidites 7, 10, and 13 were synthesized and employed in solid-phase oligonucleotide synthesis. The octa-1,7-diynyl nucleosides 1a- 4a were obtained from their corresponding iodo derivatives using the palladium-assisted Sonogashira cross-coupling reaction.

Oligonucleotides containing 6-aza-2'-deoxyuridine: synthesis, nucleobase protection, pH-dependent duplex stability, and metal-DNA formation.

Oligodeoxyribonucleotides containing the nucleoside 6-aza-2'-deoxyuridine z6Ud (1a) were prepared by using solid-phase synthesis. As the pKa value of this nucleoside is 6.8, unwanted side reactions are observed.

6-Aza-2'-deoxyuridine and N(3)-anisoyl-6-aza-2'-deoxyuridine.

In 2-(2-deoxy-beta-D-erythro-pentofuranosyl)-1,2,4-triazine-3,5(2H,4H)-dione (6-aza-2'-deoxyuridine), C(8)H(11)N(3)O(5), (I), the conformation of the glycosylic bond is between anti and high-anti [chi = -94.0 (3) degrees ], whereas the derivative 2-(2-deoxy-beta-D-erythro-pentofuranosyl)-N(4)-(2-methoxybenzoyl)-1,2,4-triazine-3,5(2H,4H)-dione (N(3)-anisoyl-6-aza-2'-deoxyuridine), C(16)H(17)N(3)O(7), (II), displays a high-anti conformation [chi = -86.4 (3) degrees].

6-azapyrimidine and 7-deazapurine 2'-deoxy-2'-fluoroarabinonucleosides: synthesis, conformation and properties of oligonucleotides.

The synthesis of 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl nucleosides (1b, 2b, and 3b) were described and their conformation in solution as well as in the solid state was determined In addition to this, building blocks 10a,b and 13a,b were prepared and employed in solid-phase oligonucleotide synthesis. For compounds 1a and 1b the lactime proton is protected to avoid unresolved degradation of its phosphoramidites 10a,b. UV-melting studies have been carried out to assess the thermal stability of oligonucleotides containing compounds 1a,b, and 3a,b.

Comparative conformational analysis of nucleosides by NMR, X-ray, and semi-empirical (PM3 VS. AM1) methods.

The 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl ortho-aza-purine and -pyrimidine nucleosides manifest an unusually rigid sugar N conformation in solution.

6-Aza-2'-deoxy-2'-arabinofluorouridine, a 2'-deoxyribonucleoside with an N-sugar conformation in the solid state and in solution.

In the title compound, 2-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-1,2,4-triazine-3,5(2H,4H)-dione, C(8)H(10)FN(3)O(5), the torsion angle of the N-glycosylic bond is anti [chi = -125.37 (13) degrees]. The furanose moiety adopts the N-type sugar pucker ((3)T(2)), with P = 359.