Syntheses and structure--activity relationships of novel apio and thioapio dideoxydidehydronucleosides as anti-HCMV agents

Synthesis and cytotoxic evaluation of apioarabinofuranosyl pyrimidines

In view of the potent anticancer activity of the d-arabino-configured cytosine nucleoside (ara-C), apioarabinofuranosyl pyrimidine nucleosides were designed and synthesized from d-ribose as starting material. The synthetic strategy signifies that tosylation followed by in situ cyclization, one-pot controlled oxidative cleavage and acetylation by Pb(OAc)₄ , stereoselective nucleobase condensation, inversion of hydroxyl group and uracil group converted to cytosine as the key steps. Synthesized apioarabinofuranosyl pyrimidine nucleosides were tested using breast, colon, and ovarian cancer cell lines. However, only compound 19a, 19b, and 22b have a moderate growth-suppressive effect against the luminal A breast cancer cell line MCF7.

Structure-Activity Relationships of Acyclic Selenopurine Nucleosides as Antiviral Agents

A series of acyclic selenopurine nucleosides 3a–f and 4a–g were synthesized based on the bioisosteric rationale between oxygen and selenium, and then evaluated for antiviral activity. Among the compounds tested, seleno-acyclovir (4a) exhibited the most potent anti-herpes simplex virus (HSV)-1 (EC₅₀ = 1.47 µM) and HSV-2 (EC₅₀ = 6.34 µM) activities without cytotoxicity up to 100 µM, while 2,6-diaminopurine derivatives 4e–g exhibited significant anti-human cytomegalovirus (HCMV) activity, which is slightly more potent than the guanine derivative 4d, indicating that they might act as prodrugs of seleno-ganciclovir (4d).

Nucleosides with Transposed Base or 4'-Hydroxymethyl Moieties and Their Corresponding Oligonucleotides

This review focuses on 4'-hydroxymethyl- or nucleobase-transposed nucleosides, nucleotides, and nucleoside phosphonates, their stereoisomers, and their close analogues. The biological activities of all known 4'-hydroxymethyl- or nucleobase-transposed nucleosides, nucleotides, and nucleoside phosphonates as potential antiviral or anticancer agents are compiled. The routes that have been taken for the chemical synthesis of such nucleoside derivatives are described, with special attention to the innovative strategies. The enzymatic synthesis, base-pairing properties, structure, and stability of oligonucleotides containing nucleobase- or 4'-hydroxymethyl-transposed nucleotides are discussed. The use of oligonucleotides containing nucleobase- or 4'-hydroxymethyl-transposed nucleotides as small oligonucleotide (e.g., human immunodeficiency virus integrase) inhibitors, in applications such as antisense therapy, silencing RNA (siRNA), or aptamer selections, is detailed.

Selenoacyclovir and Selenoganciclovir: Discovery of a New Template for Antiviral Agents

On the basis of the potent antiviral activity of acyclovir and ganciclovir, selenoacyclovir (2a) and selenoganciclovir (2b) were designed based on bioisoteric rationale and synthesized via the diselenide 7 as the key intermediate. Compound 2a exhibited potent anti-HSV-1 and -2 activities while 2b exerted moderate anti-HCMV activity, indicating that these nucleosides can serve as a novel template for the development of new antiviral agents.

Design, synthesis and anti-HIV activity of homologous PMEA derivatives

This article describes an efficient route for synthesizing novel cyclopropyl homologous PMEA analogues. The condensation of the bromide 8 with nucleosidic bases (A, U, T, C, 5-FU, G) under standard nucleophilic substitution and deprotection conditions, afforded the target phosphonic acid analogues 14 approximately 18 and 21. These compounds were evaluated for their potential antiviral properties against various viruses. Guanine derivative 21 showed significant antiviral activity.

Asymmetric synthesis of novel apio carbocyclic nucleoside analogues as potential antiviral and antitumor agent

Novel apio carbocyclic nucleosides 18-21 were asymmetrically synthesized as potential antiviral and antitumor agent, starting from D-ribose employing aldol reaction, RCM reaction and Mitsunobu reaction as key reactions.

Synthesis, DNA Binding and Antiviral Activity of New Uracil, Xanthine, and Pteridine Derivatives

Some new 6-amino-1,3-dimethyl-5-(substituted methylidene)aminouracils were synthesized. Most of them were cyclized with triethyl orthoformate as a one-carbon source to afford 1,3-dime-thyl-6-substituted pteridine derivatives. Certain uracils gave xanthine instead of the expected pteridine derivatives upon using another one-carbon source such as triethyl orthoacetate or triethyl orthobenzoate. The nucleic acid binding assay revealed that some new compounds showed high affinity, chelation, and fragmentation of nucleic acids whether DNA or RNA contrary to acyclovir that has affinity to DNA only. The antiviral activity of these novel compounds showed that compounds 2e and 2f reduced the cytopathogencity of Peste des petits ruminant virus (PPRV) on Vero cell culture by 60 and 50%, respectively.

Simple synthesis and anti-HIV activity of novel cyclopentene phosphonate nucleosides

A very simple synthetic route for novel cyclopentene phosphonate nucleosides is described. The characteristic cyclopentene moiety 6 was constructed via a ring-closing metathesis of divinyl 5, which could be readily prepared from diethylmalonate. The condensation of the mesylate 11 with nucleobases (A, C, T, U) under nucleophilic substitution conditions (K2CO3, 18-Crown-6, DMF) afforded the target nucleosides 12, 13, 14, and 15. In addition, the antiviral evaluations against various viruses were performed.

Streptavidin chiral stationary phase for the separation of adenosine enantiomers

In this paper, a microbore column packed with streptavidin particles was used, at various temperatures (0-24 degrees C), to separate the adenosine enantiomers by HPLC. Using an aqueous mobile phase, the apparent enantioseparation was high for a small molecule, varying from 11.5 at 0 degrees C to 6.2 at 24 degrees C. From the experiments carried out with a streptavidin-biotin complex stationary phase, it was demonstrated that the blockage of the biotin sites of the immobilized streptavidin was responsible for a strong decrease in the enantioselectivity via a direct and/or an indirect effect. From the analysis of the concentration dependencies of the solute retention factor, it was also shown that a reduction of the D-adenosine specific binding sites occurred at the lowest temperature. The thermodynamic parameters determined from the van't Hoff plots indicated that the D-adenosine binding to the streptavidin specific sites was enthalpically driven.

C4‘-Spiroalkylated Nucleosides Having Sulfur Incorporated at the Apex Position

Methodology based on the concept of thionium ion-initiated pinacolic ring expansion has been developed for accessing C4'-spirocyclic thionucleosides. The readily available racemic ketones 6 and 37 are conveniently resolved via their acetals with (R)-mandelic acid. Subsequent reactions beginning with utilization of the Pummerer rearrangement lend themselves to functionalization of the spirocyclic core and ultimately incorporation of the nucleosidic bases. Limitations to this strategy are pointed out. Acquisition of the alpha- and beta-isomers at C4' is equally facile. Absolute configurational assignments have been made possible by X-ray crystallography.

Synthesis of novel apionucleosides: a short and concise synthesis of 2-deoxyapio-L-furanosyl acetate from D-lactose

A series of 2'-deoxyapio-L-furanosyl pyrimidine nucleosides were efficiently synthesized starting from D-lactose via condensation of lactitor acetates with silylated pyrimidine bases under standard Vorbrüggen conditions. Their structures were determined by 1D and 2D NMR spectroscopy. All the synthesized nucleosides were assayed against several viruses such as HIV-1, HBV, HSV-1, HSV-2, and HCMV. However, none of these compounds had any significant antiviral activity at concentrations up to 100 microM.

Synthesis and biological evaluation of novel thioapio dideoxynucleosides

On the basis of the bioisosteric rationale to apio dideoxynucleosides, novel thioapio dideoxynucleosides have been synthesized, starting from 1,3-dihydroxyacetone via thioapio sugar acetate as a key intermediate. The intermediate was condensed with silylated pyrimidine bases such as N(4)-benzoylcytosine, uracil or thymine in the presence of TMSOTf to give the beta-anomers and alpha-anomers, respectively. The intermediate was also condensed with silylated 6-chloropurine to give the 6-chloropurine derivatives and which were converted to adenine derivatives and, N(6)-methyladenine derivatives and, and hypoxanthine derivatives and, respectively. The guanine analogues and were also synthesized from the condensation of sugar acetate with 2-acetamido-6-chloropurine. All synthesized final compounds were tested against HIV-1. Most of the synthesized compounds exhibited toxicity-dependent anti-HIV-1 activity, among which 6-chloropurine derivative was found to be the most cytotoxic and showed good cytotoxicity against colon cancer cell lines. Although we could not find good anti-HIV agents in this study, findings of some anticancer activity in this series will allow this class of nucleosides to be the new template for the development of new anticancer agents (Fig. 1).

Synthesis of novel (2R,4R)- and (2S,4S)-iso dideoxynucleosides with exocyclic methylene as potential antiviral agents

Novel (2R,4R)- and (2S,4S)-iso dideoxynucleosides with exocyclic methylene have been designed and synthesized, based on the lead BMS-200475 (3) which exhibited potent anti-HBV activity. For the synthesis of D types of (2R,4R)-nucleosides, L-xylose was converted to the key intermediate 14. The intermediate 14 was converted to the uracil derivative 4a and the cytosine derivative 4b. Compound 14 was also converted to the purine derivatives such as adenine derivative 4c, hypoxanthine derivative 4d, and guanine derivative 4e. The corresponding L types of (2S,4S)-enantiomers were more efficiently synthesized from the commercially available 1,2-isopropylidene-D-xylose (20) than the synthetic method used in the synthesis of (2R,4R)-nucleosides. The key intermediate 25 was converted to the pyrimidine analogues 5a and 5b and the purine derivatives 5c, 5d, and 5e using the similar method used in the preparation of 4c, 4d, and 4e. The synthesized final (2R,4R)- and (2S,4S)-nucleosides were tested against several viruses such as HIV-1, HSV-1, HSV-2, HCMV and HBV. (2R,4R)-Adenine analogue 4c exhibited potent anti-HBV activity (EC(50)=1.5 microM in 2.2.15 cells) among compounds tested, while (2R,4R)-uracil derivative 4a was the most active against HCMV among compounds tested and (2R,4R)-adenine derivative 4c was found to be moderately active against the same virus. However, the corresponding (2S,4S)-isomers were found to be totally inactive against all tested viruses. Both (2R,4R)-adenine derivative 4c and (2S,4S)-adenine analogue 5c were totally resistant to the adenosine deaminase like iso-ddA (1). From the molecular modeling study the hydroxymethyl side chains of BMS-200475 (3) and 4c were almost overlapped, indicating that 4c may be suitable for phosphorylation by cellular kinases like the lead 3, but some discrepancy between two bases was observed, indicating why 4c is less potent against HBV than 3. It is concluded that discovery of (2R,4R)-adenine analogue 4c as potent anti-HBV agent suggested that the sugar moiety of this series can be regarded as a novel template for the development of new anti-HBV agent and oxygen atom can be acted as a bioisostere of C-OH.

Synthesis and antiviral activity of fluoro-substituted apio dideoxynucleosides

Novel fluoro-substituted apio dideoxynucleosides ((+/-)-3a and (+/-)-3b) were efficiently synthesized starting from 1,3-dihydroxyacetone via Horner-Emmons olefination as a key step. Cyclization of fluoro ester (+/-)-6 under acidic conditions to the fluorolactone was smoothly proceeded in favor of trans-fluorolactone due to the favorable transition state with equatorial hydroxymethyl substituent. Unfortunately, the final nucleosides (+/-)-3a and (+/-)-3b were found to be inactive against several viruses such as HIV-1, HSV-1, HSV-2 and HCMV.