Nucleotides. Part IL. Synthesis and Characterization of Cordycepin‐Trimer‐Vitamin and ‐Lipid Conjugates Potential Inhibitors of HIV‐1 Replication

Abstract

The syntheses of biodegradable 2 -and 5'-ester and 2 -and 5'-carbonate conjugates of the antivirally active 3'-deoxyadenylyl-(2'5')-3'-deoxyadenylyl-(2'-5')-3'-deoxyadenosine (cordycepin-trimer core) with the vitamins, E, D,, and A and the lipids 1,2-di-0 -palmitoylglycerol and 1,2-di-0 -hexadecylglycerol were achieved first by preparation of the trimeric educts 19-21 (Scheme 1). Secondly, these substances were condensed with the lipophilic residues via a succinate or carbonate linker and then deprotected byp -elimination of the npeoc and npe protecting groups and acid treatment for detritylation without harming the ester and carbonate functions, respectively (Scheme 2). Metabolically stable cordycepin-trimer-vitamin and -lipid conjugates are a new class of bioconjugates that inhibit HIV-1-induced syncytia formation with IC,, values of 7, 18, and 24 p~ for 39,29, and 42, respectively, and inhibit HIV-1 reverse transcriptase (RT) activity from 14 to 96% (see Table). Of the nine conjugates tested, inhibition of HIV-1 replication by 28,29,32,40, and 42 may be attributed in part to the activation of the RNase LjPKR antiviral pathways. Trimer conjugate 42 showed the greatest inhibition of HIV-1 replication, i.e., a 120-fold decrease in HIV-I-induced syncytia formation and an 88 % inhibition of HIV-1 reverse transcriptase (RT). This inhibition of replication of HIV-1 by 42 can be attributed in part to the activation of recombinant, human RNase L. The inhibition of HIV-1 replication by the cordycepin-trimer-vitamin and -lipid conjugates is significantly greater than that observed for the (2-5') A-trimer core or cordycepin-trimer core.

Nucleolipids: Natural Occurrence, Synthesis, Molecular Recognition, and Supramolecular Assemblies as Potential Precursors of Life and Bioorganic Materials

“…In a subsequent publication Pfleiderer, Suhadolnik, and co-workers reported on the synthesis of a series of cordycepin ± vitamin and cordycepin ± lipid conjugates (147 ± 157) [53] [54]. For this purpose, cordycepin ( 3'-deoxyadenosine; 119) was modified at the 2'-O-and 5'-O-position by the hydrophobic vitamins E, D 2 , and A, and by the two lipids, 1,2-di-O-palmitoylglycerol, and 1,2-di-O-hexadecylglycerol, via succinate or carbonate linkages.…”

Nucleotides Part LXX

“…Elution with toluene/AcOEt 9 : 1, 8 : 2, and 7 : 3 gave 0.42 g (16%) of 9, elution with toluene/AcOEt 65 : 35 gave 0.67 g (30%) of 10, and elution with toluene/AcOEt 3 : 2 gave 0.94 g (42%) of 11 as colorless foams. (12). A soln.…”

“…The level of HIV-1 p24 antigen was measured in cell-culture supernatents by the antigen-capture ELISA assay (SAIC-Frederick). Recombinant human RNase L was expressed in E. coli (DH5a) as a glutathione-S-transferase(GST)-RNase L fusion protein as described [11] [12]. 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].…”

“…Recombinant human RNase L was expressed in E. coli (DH5a) as a glutathione-S-transferase(GST)-RNase L fusion protein as described [11] [12]. 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).…”

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 .…”