Nucleotides. Part XLIV. Synthesis, characterization, and biological activity of monomeric and trimeric cordycepin‐cholesterol conjugates and inhibition of HIV‐1 replication

Abstract

The antivirally active 3'-deoxyadenylyl-(2'-5')-3'-deoxyadenylyl-(2'-5')-3'-deoxyadenosine (cordycepin trimer core) was modified at the 2'-or 5'-terminus, by attachment of cholesterol via a carbonate bond (+ 15) or a succinate linker (-+ 16 and 27) to improve cell permeability. The corresponding monomeric conjugates 4,7, and 21 of cordycepin were prepared as model substances to study the applicability of the anticipated protecting groups the monomethoxytrityl (MeOTr), the (rert -butyl)dimethylsilyl (tbds), and the / J ' -eliminating 2-(4-nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) groups ~ for the final deblocking steps without harming the ester bonds of the conjugate trimers. The syntheses were performed in solution using phosphoramidite chemistry. The fully protected trimer conjugates 13, 14, and 26 as well as all intermediates were characterized by elemental analyses, UV and 'H-NMR spectra. The deblocked conjugates 15, 16, and 27 were pure according to HPLC and showed the correct compositions by mass spectra. Comparative biological studies indicated that cordycepincholesterol conjugate trimers 16 and 27 were 333-and 1000-fold, respectively, more potent inhibitors of HIV-I-induced syncytia formation than cordycepin trimer core.

Nucleotides Part LI. Synthesis and biological activities of (2′‐5′)adenylate trimer conjugates with 2′‐terminal 3′‐O(ω‐hydroxyalkyl) and 3′‐O‐(ω‐carboxyalkyl) spacers

“…(50 ml H 6.16, N 6.11; found: C 78.56, H 6.00, N 6.25. (14). In THF/EtOH/lM NaOH 2: 2: 1 (100 ml), 13 (6.4 g, 5.6 mmol) was kept at r.t. for 4 h. Then the mixture was neutralized with AcOH, diluted with CHC1, (250 ml), and washed with sat.…”

Synthesis and Deprotection of Biodegradably and Thermally Protected Dinucleoside‐2′,5′‐Monophosphate Prodrug Model of 2‐5A

“…Numerous modified 2‐5A pro‐nucleotides, such as phosphorothioate, alanyltyrosine, 2′‐ O ‐phosphoglyceryl, 5′‐capped, aminofuctionalized and phosphoramidate derivatives as well as 3′‐deoxyadenosine, 3′‐ O ,4‐C‐bridged adenosine, 3′‐fluoro‐3‐deoxyadenosine, 3′‐ O ‐methyladenosine and 3′‐amino‐3′‐deoxyadenosine analogues have been synthesized to increase the stability in serum and cytoplasm. Several techniques have also been tested to enhance the cell delivery of 2‐5A and their modified analogues, as an example, encapsulation in liposomes and conjugation to lipophilic groups, but no satisfactory prodrug strategy for the enhancement of cellular uptake has been developed. Generally, most of the prodrug approaches of nucleoside 5′‐phosphomonoesters and 3′,5′‐phosphodiesters are based on enzymatic transformation that triggers a chemical removal of the remnants of phosphate protecting group .…”

Nucleotides Part LXX

“…± Inhibition of HIV-1 Replication. The infected-centers assay was used to measure the ability of 37 ± 40 to inhibit HIV-1-induced syncytia formation, and PCR-amplification and HIV-1-integrase assays were accomplished as previously described [34]. The level of HIV-1 p24 antigen was measured in cell-culture supernatents by the antigen-capture ELISA assay (SAIC-Frederick).…”

“…The activation of recombinant human GST-RNase L was measured as the percent of poly(U)-3'-[ 32 P]pCp hydrolyzed in the presence of p 3 A 3 (1 ¥ 10 À10 to 10 À6 m) or (2'-5')A derivatives, as previously described [11] [12]. The effect of (2'-5')A derivatives on HIV-1 reverse-transcriptase (RT) activity was measured as reported [34], except that test compounds (100 mm) were added 2 h prior to infection of peripheral blood mononuclear cells (PBMC) (2 ¥ 10 5 ) with HIV-1 IIIB (m.o.i.0.1).…”