Relationship between structural properties and affinity for herpes simplex virus type 1 thymidine kinase of bromine substituted 5-heteroaromatic 2'-deoxyuridines.

The crystal structures of 5-(5-furan-2-yl)-2'-deoxyuridine (II), 5-(5-bromofuran-2-yl)-2'-deoxyuridine (IV) and 5-(3-bromothien-2-yl)-2'-deoxyuridine (V) have been studied in order to explain the different affinity of the compounds for the herpes simplex virus type 1 (HSV-1) thymidine kinase. These compounds present a variable affinity according to the position of the heteroatom substituting the five-membered ring. An unfavourable substitution in the five-membered ring for interaction with the HSV-1 thymidine kinase has been identified.

Stereoelectronic properties of five anti-HSV-1 2'-deoxynucleosides analogues with heterocyclic substituents in the 5-position: a comparison with BVDU.

Structural and electronic characteristics of 5-(5-chlorothien-2-yl)-2'-deoxyuridine (I), 5-(furan-2-yl)-2'-deoxyuridine (II), 5-(5-bromofuran-2-yl)-2'-deoxyuridine (III), 5-(3-bromoisoxazol-5-yl)-2'-deoxyuridine (V) and 5-(isoxazol-5-yl)-2'-deoxyuridine (IV) have been determined and compared to the BVDU (VI) characteristics in order to explain their respective affinity for the herpes simplex virus type 1 thymidine kinase (TK). Molecular structure of 5-(5-chlorothien-2-yl)-2'-deoxyuridine has been obtained using single crystal X-ray crystallography. Electrostatic potential maps, energy and topology of frontier orbitals were computed at the ab initio MO STO-3G and STO-3G level. These studies reveal that the electrostatic potential energy maps are clearly dependent on the affinity of the compound for the enzyme.

Mechanism of cytostatic action of novel 5-(thien-2-yl)- and 5-(furan-2-yl)-substituted pyrimidine nucleoside analogues against tumor cells transfected by the thymidine kinase gene of herpes simplex virus.

Several novel 5-substituted 2'-deoxyuridine (dUrd) analogues were evaluated as substrates for highly purified herpes simplex virus type 1 (HSV-1)-encoded thymidine kinase (TK) derived from HSV-1 TK gene-transfected murine mammary carcinoma FM3A cells, and human platelet thymidine (dThd) phosphorylase. The Ki of 5-(furan-2-yl)-dUrd, 5-(thien-2-yl)-dUrd and 5-(thien-2-yl)-dCyd for HSV-1 TK was 0.94, 0.71, and 1.32 microM, respectively. Inhibition was competitive with respect to the natural substrate dThd. With dCyd as substrate, the Ki of 5-(thien-2-yl)-dCyd for HSV-1 TK was 4.5 microM (Ki/Km = 0.17). In striking contrast with (E)-5-(2-bromovinyl)-dUrd, the 5-(thien-2-yl)- and 5-(furan-2-yl)-dUrd derivatives were not substrates for human dThd phosphorylase. 5-(Thien-2-yl)-dUrd, 5-(furan-2-yl)-dUrd and 5-(thien-2-yl)-dCyd were at least 100-fold more cytostatic to the HSV TK gene-transfected FM3A tumor cells than wild-type FM3A/0 cells. The viral TK expressed in the HSV-1 TK gene-transfected tumor cells merely acts as an activating enzyme, whereas thymidylate synthase serves as the target enzyme for the cytostatic action of the compounds. The novel 5-substituted dUrd analogues should be further pursued as candidate drugs in the treatment of HSV TK gene-transfected tumors.

Synthesis and antiviral activity of 5-thien-2-yl-2'-deoxyuridine analogues.

A number of 5-heteroaromatic-substituted 2'-deoxyuridines were synthesized from 5-iodo-2'-deoxyuridine using tetraorganotin reagents and palladium complexes as catalyst. The palladium-catalyzed cross-coupling reaction between 5-iodo-2'-deoxyuridine and stannylated heteroaromatics was optimized for the synthesis of the 5-thien-3-yl-2'-deoxyuridine and 5-furan-3-yl-2'-deoxyuridine. 5-(5-Iodothien-2-yl)-2'-deoxyuridine was used as starting material for the synthesis of 5-(5-methylthien-2-yl)-2'-deoxyuridine, 5-(5-vinylthien-2-yl)-2'-deoxyuridine, and 5-(5-ethynylthien-2-yl)-2'- deoxyuridine. 5-(5-Nitrothien-2-yl)-2'-deoxyuridine was synthesized using ceric ammonium nitrate as reagent. 5-(Isoxazol-5-yl)-2'-deoxyuridine was synthesized from 5-(3-oxopropyn-1-yl)-2'-deoxyuridine. Finally, 5-(5-chlorothien-2-yl)-beta-D-arabinofuranosyluracil and 5-(5-bromothien-2-yl)-beta-D-arabinofuranosyluracil were obtained by halogenation of 5-thien-2-yl-beta-D-arabinofuranosyluracil. Introduction of an alkyl substituent in the 5-position of the thienyl group of 5-thien-2-yl-2'-deoxyuridine or substitution of the 2-deoxyribofuranose ring by an arabinofuranose moiety gave decreased activity against HSV-1 and VZV replication when compared with the 5"-halogenated-5-thien-2-yl-2'-deoxyuridines. 5-(5-Bromothien-2-yl)-2'-deoxyuridine caused prompt healing of HSV-1 keratitis when administered as eye drops (0.2%) to rabbits.

5-(5-Bromothien-2-yl)-2'-deoxyuridine and 5-(5-chlorothien-2-yl)-2'-deoxyuridine are equipotent to (E)-5-(2-bromovinyl)-2'-deoxyuridine in the inhibition of herpes simplex virus type I replication.

2'-Deoxyuridines with a five-membered heterocyclic substituent in the 5-position were synthesized by palladium-catalyzed coupling reactions of 5-iodo-2'-deoxyuridine with the activated heteroaromatics. Further modification of the compound with the 5-thien-2-yl substituent gave 5-(5-bromothien-2-yl)-2'-deoxyuridine and 5-(5-chlorothienyl-2-yl)-2'-deoxyuridine. Both compounds show potent and selective activity against herpes simplex virus type 1 and varicella-zoster virus.

Synthesis and antiviral activity of 5-heteroaryl-substituted 2'-deoxyuridines.

The synthesis of 5-heteroaryl-substituted 2'-deoxyuridines is described. The heteroaromatics were obtained from three different 5-substituted 2'-deoxyuridines. Cycloaddition reaction of nitrile oxides on the 5-ethynyl derivative 1 gave the isoxazoles 4a-e. The thiazole derivatives 14a-c were obtained from the 5-thiocarboxamide 11, while 5-pyrrol-1-yl-2'-deoxyuridine (17) could be synthesized directly from 5-amino-2'-deoxyuridine. The compounds were evaluated for antiviral activity. Selective activity against herpes simplex virus type 1 (HSV-1) and varicella zoster virus (VZV) was noted for 5-(3-bromoisoxazol-5-yl)-2'-deoxyuridine (4c). The compound was inactive against herpes simplex virus type 2, cytomegalovirus, and thymidine kinase (TK)-deficient mutants of HSV-1 and VZV, which indicates that, most likely, its antiviral activity depends on phosphorylation by the virus-specified TK.

Synthesis and antiviral activity of 3'-heterocyclic substituted 3'-deoxythymidines.

Various 3'-deoxythymidine analogues with an heterocyclic five-membered ring in the 3'-erythro position have been synthesized. The pyrrol-1-yl (3) and the 1,2,4-triazol-4-yl (5) compounds were synthesized from 1-(3-amino-2,3-dideoxy-beta-D-erythro-pentofuranosyl)thymine. The pyrazol-1-yl (16a), imidazol-1-yl (16b), and 1,2,4-triazol-1-yl (16c) derivatives were obtained by epoxide opening of the corresponding 1-(2,3-anhydro-beta-D-lyxofuranosyl)thymines followed by 2'-deoxygenation. Only the 3'-pyrrol-1-yl derivative showed marginal antiviral activity against human immunodeficiency virus.