Synthesis and properties of 5-(1,2-dihaloethyl)-2′-deoxyuridines and related analogues

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues

This review article summarizes the results of a long-term investigation of 5-alkoxymethyluracil analogues and is aimed, in particular, at methods of syntheses. Most of the presented compounds were synthesized in order to evaluate their biological activity, therefore, a brief survey of biological activity, especially antiviral, cytotoxic and antibacterial, is also reported.

The unabated synthesis of new nucleoside analogues with antiviral potential: a tribute to Morris J. Robins

The furo[2,3-d]pyrimidin-2(3H)-one is the key structural determinant in the exquisitely potent activity of its derivatives (R = 2-deoxyribosyl; R' = p-pentylphenyl) against VZV (varicella-zoster virus) replication. [structure: see text].

Aryl furano pyrimidines: the most potent and selective anti-VZV agents reported to date

Bicyclic aryl furano pyrimidines represent the most potent anti-VZV agents reported to date. Lead compounds have EC50 values in vitro as low as 0.1 nM and selectivity index values exceeding one million. They have an absolute requirement for VZV thymidine kinase (TK) and most likely act as their phosphate forms. Some structural modification, such as aryl substitution, is tolerated, while little sugar modification is acceptable. We herein summarise their biological profiles and structure activity relationships as discovered to date.

Synthesis and in vitro anti-mycobacterial activity of 5-substituted pyrimidine nucleosides

Mycobacterium tuberculosis and Mycobacterium avium infections cause the two most important mycobacterioses, leading to increased mortality in patients with AIDS. Various 5-substituted 2'-deoxyuridines, uridines, 2'-O-methyluridine, 2'-ribofluoro-2'-deoxyuridines, 3'-substituted-2',3'-dideoxy uridines, 2',3'-dideoxyuridines, and 2',3'-didehydro-2',3'-dideoxyuridines were synthesized and evaluated for their in vitro inhibitory activity against M. bovis and M. avium. 5-(C-1 Substituted)-2'-deoxyuridine derivatives emerged as potent inhibitors of M. avium (MIC90 = 1-5 microg/mL range). The nature of C-5 substituents in the 2'-deoxyuridine series appeared to be a determinant of anti-mycobacterial activity. This new class of inhibitors could serve as useful compounds for the design and study of new anti-tuberculosis agents.

Chemotherapy of varicella-zoster virus by a novel class of highly specific anti-VZV bicyclic pyrimidine nucleosides

(E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) is a potent inhibitor of herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV). Its mechanism of action is based on a specific conversion to its 5'-mono- and 5'-diphosphate derivative by HSV-1- and VZV-encoded thymidine kinase, and after further conversion to its 5'-triphosphate derivative, inhibition of the viral DNA polymerase and eventual incorporation into the viral DNA. Recently, a new structural class of bicyclic pyrimidine nucleoside analogues (designated BCNAs) with highly specific and selective anti-VZV activity in cell culture has been discovered. The compounds need a long alkyl or alkylaryl side-chain at the base moiety for pronounced biological activity. This property makes these compounds highly lipophilic. They are also endowed with fluorescent properties when exposed to light with short UV wavelength. In striking contrast to BVDU, the members of this class of compounds are active only against VZV, but not against any other virus, including the closely related HSV-1, HSV-2 and cytomegalovirus. The most active compounds inhibit VZV replication at subnanomolar concentrations and are not toxic at high micromolar concentrations. The compounds lose their antiviral activity against thymidine kinase (TK)-deficient VZV strains, pointing to a pivotal role of the viral TK in their activation (phosphorylation). Kinetic studies with purified enzymes revealed that the compounds were recognized by VZV TK as a substrate, but not by HSV-1 TK, nor by cytosolic or mitochondrial TK. VZV TK is able to phosphorylate the test compounds not only to their corresponding 5'-mono- but also to their 5'-diphosphate derivatives. These data may readily explain and rationalize the anti-VZV selectivity of the BCNAs. There is no clear-cut correlation between the antiviral potency of the compounds and their affinity for VZV TK, pointing to a different structure/activity relationship of the eventual antiviral target of these compounds. The compounds are stable in solution and, in contrast to BVDU, not susceptible to degradation by thymidine phosphorylase. The bicyclic pyrimidine nucleoside analogues represent an entirely new class of highly specific anti-VZV compounds that should be further pursued for clinical development.

Synthesis of unnatural 7-substituted-1-(2-deoxy-beta-D-ribofuranosyl)isocarbostyrils: "thymine replacement" analogs of deoxythymidine for evaluation as antiviral and anticancer agents

A group of unnatural 1-(2-deoxy-beta-D-ribofuranosyl)isocarbostyrils having a variety of C-7 substituents [H, 4,7-(NO2)2, I, CF3, CN, (E)-CH=CH-I, -C triple bond CH, -C triple bond C-I, -C triple bond C-Br, -C=C-Me], designed as nucleoside mimics, were synthesized for evaluation as anticancer and antiviral agents. This class of compounds exhibited weak cytotoxicity in a MTT assay (CC50 = 10(-3) to 10(-5) M range) with the 4,7-dinitro derivative being the most cytotoxic, relative to thymidine (CC50 = 10(-3) to 10(-5) M range), against a variety of cancer cell lines. The 4,7-dinitro, 7-I and 7-C triple bond CH compounds exhibited similar cytotoxicity against non-transfected (KBALB, 143B), and HSV-1 TK+ gene transfected (KBALB-STK, 143B-LTK) cancer cell lines possessing the herpes simplex virus type 1 (HSV-1) thymidine kinase gene (TK+). This observation indicates that these compounds are not substrates for HSV type-1 TK, and are therefore unlikely to be useful in gene therapy based on the HSV gene therapy paradigm.

Furano pyrimidines as novel potent and selective anti-VZV agents

Bicyclic furano pyrimidine nucleosides have been found to be highly potent and selective inhibitors of varicella zoster virus (VZV). They are inactive against herpes simplex virus and have been known for several decades as (unwanted) synthetic by-products in the Pd-catalysed coupling of acetylenes to 5-iodo nucleosides. These fluorescent bicyclic nucleosides are now established as a new family of potent antivirals. They are unusual in that they exhibit complete specificity for VZV and require an alkyl (or alkylaryl) side-chain for biological activity. The latter requirement confers extremely high lipophilicities on these compounds, unknown amongst chemotherapeutic nucleosides, which may be of considerable importance in formulation, dosing and tissue distribution. The most potent compounds reported are p-alkylaryl compounds, with EC50 values below 1 nM versus VZV and selectivity index values of around 1,000,000. Here, we review the discovery, synthesis, characterization, antiviral profile, SAR, mechanism of action and development prospects for this new family of antivirals.

Synthesis and anti-varicella-zoster virus activity of some novel bicyclic nucleoside inhibitors: effect of enhanced aqueous solubility

We have recently reported the discovery of an entirely new category of potent antivaricella-zoster virus agents based on novel deoxynucleoside analogues bearing unusual fluorescent bicyclic furo base moieties. Initial studies revealed an absolute requirement of a long alkyl side-chain, with an optimal length of C8-C10, for antiviral activity. However, the impact of this requirement on the physical properties of these compounds is high: inherent lipophilicity and extremely poor aqueous solubility, which may limit the use of these nucleosides as drugs. In order to address this issue, we have now prepared a new series of analogues, bearing ether and glycol type side-chains, designed to improve the aqueous solubility of the compounds. Synthesis of target nucleosides involved Pd-catalysed coupling of terminal alkynes with 5-iodo-2'-deoxyuridine. The 5-alkynyl nucleosides thus obtained were then treated with copper (I) iodide to produce the desired bicyclic analogues. As anticipated, the new compounds exhibited a dramatic increase in aqueous solubility, although antiviral activity was significantly reduced. A possible correlation between antiviral activity and overall compound lipophilicity is discussed.

Anti-varicella-zoster virus bicyclic nucleosides: replacement of furo by pyrro base reduces antiviral potency

We have recently reported the discovery of an entirely new category of potent antiviral agents based on novel deoxynucleoside analogues with unusual fluorescent bicyclic furo base moieties. To probe structure-activity relationships and to seek to optimize the properties of the lead compounds, we prepared pyrro analogues of the furo systems. We herein report the synthesis, characterization and antiviral evaluation of these novel compounds.

Synthesis of 5-(1-azidovinyl) and 5-[2-(1-azirinyl)] analogs of 2′-deoxyuridine

The regiospecific addition of bromine azide to the vinyl substituent of 5-vinyl-3′,5′-di-O-acetyl- (or tert-butyldimethylsilyl)-2′-deoxyuridines (2) yielded the corresponding 5-(1-azido-2-bromoethyl)-3′,5′-di-O-protected-2′-deoxyuridines (3). Treatment of the 5-(1-azido-2-bromoethyl) compounds 3 with t-BuOK, to effect the base-catalyzed elimination of HBr, afforded the corresponding 5-(1-azidovinyl)-2′-deoxyuridines (4, 7). Thermal decomposition of 5-(1-azidovinyl)-2′-deoxyuridine (7) at 110 °C in dioxane yielded 5-[2-(1 -azirinyl)]-2′-deoxyuridine (9). 5-(1 -Azidovinyl)-2′-deoxyuridine (7) exhibited appreciable in vitro antiviral activities againist herpes simplex virus type 1 (HSV-1) and varizella zoster virus (VZV). Athough 7 increased the length of survival of HSV-1 brain-infected mice, it did not decrease the mortality rate relative to placebo. 5-[2-(1-Azirinyl)]-2′-deoxyuridine (9) was an inactive antiviral agent. Key words: azidovinyl, azirinyl, 2′-deoxyuridine, antiviral activity.