Synthesis and anti-herpes virus activity of 2'-deoxy-4'-thiopyrimidine nucleosides.

A series of 5-substituted 2'-deoxy-4'-thiopyrimidine nucleosides was synthesized and evaluated as potential antiviral agents. A number of analogues such as 2'-deoxy-5-propyl-4'-thiouridine (3ii), 2'-deoxy-5-isopropyl-4'-thiouridine (3iii), 5-cyclopropyl-2'-deoxy-4'-thiouridine (3iv), 2'-deoxy-4'-thio-5-vinyluridine (3viii), and 5-(2-chloroethyl)-2'-deoxy-4'-thiouridine (3xx) were found to be highly active against herpes simplex virus type-1 (HSV-1) and varicella zoster virus (VZV) in vitro with no significant cytotoxicity. The compound with the broadest spectrum of activity was 2'-deoxy-5-ethyl-4'-thiouridine (3i) which showed significant activity against HSV-1, HSV-2, and VZV.

Isosteres of the DNA polymerase inhibitor aphidicolin as potential antiviral agents against human herpes viruses.

A variety of isosteres of the DNA polymerase inhibitor aphidicolin were synthesized as potential antiherpes agents. Modeling studies indicated that the bicyclooctane C, D rings of aphidicolin could be replaced by an aromatic moiety while maintaining the spatial arrangement of the hydroxyl group equivalent to the essential C18 hydroxyl group of aphidicolin. Of the racemic isosteres synthesized only 13, the compound with the greatest structural similarity to aphidicolin, showed any significant antiviral activity in primary assays. An enantioselective synthesis of the compound was carried out and the 4aS isomer 36 was shown to account for the observed antiviral activity noted against herpes simplex virus 1 and human cytomegalovirus.

Synthesis and antirhinovirus activity of 8-substituted analogues of 6-(dimethylamino)-9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine.

Several 8-substituted analogues of 6-(dimethylamino) -9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine (1) were synthesized and tested for activity against rhinovirus type 1B. Among 16 8-substituted analogues, the 8-amino (3) and 8-bromo (2) analogues were most active with IC50s of 0.36 and 1.4 microM, respectively, under conditions where 1 had an IC50 of 0.03 microM.

Antirhinovirus activity of 6-anilino-9-benzyl-2-chloro-9H-purines.

A series of 6-anilino-9-benzyl-2-chloropurines was synthesized and tested for antirhinovirus activity. Most of the compounds were prepared by reaction of the appropriate aniline with 9-benzyl-2,6-dichloro-9H-purine. Structure-activity relationship studies revealed that compounds with small, lipophilic para substituents were good inhibitors of serotype 1B. Several compounds had good activity against four representative serotypes.

Synthesis and antirhinovirus activity of 6-(dimethylamino)-2-(trifluoromethyl)-9-(substituted benzyl)-9H-purines.

A series of 6-(dimethylamino)-2-(trifluoromethyl)-9-(substituted benzyl)purines was synthesized and tested for antirhinovirus activity. Most of the compounds were synthesized by alkylation of 6-chloro-2-(trifluoromethyl)-9H-purine with the appropriate benzyl halide followed by displacement of the chloro group with dimethylamine. Alternatively, 6-(dimethylamino)-2-(trifluoromethyl)purine was alkylated with the appropriate benzyl halide. Although several different aryl substituents provided compounds with IC50's = 0.03 microM against rhinovirus serotype 1B, no congener was significantly more active than the parent 2. Twenty-three compounds were tested against 18 other serotypes, but none exhibited a uniform profile of activity.

Synthesis and structure-activity relationships of 2-substituted-6-(dimethylamino)-9-(4-methylbenzyl)-9H-purines with antirhinovirus activity.

A series of 2-substituted-6-(dimethylamino)-9-(4-methylbenzyl)-9H-purines where the 2-substituent was H, F, Cl, CF3, CH3, CH2CH3, NH2, NHCH3, N(CH3)2, SCH3, or SO2CH3 was synthesized and tested for antirhinovirus activity to evaluate the effect of 2-substituents on antiviral activity. Intuitive and quantitative structure-activity relationship (QSAR) analysis showed that optimum antirhinovirus serotype 1B activity was associated with 9-benzylpurines that contained a C-2 lipophilic, electron-withdrawing substituent. The most active compound, 6-(dimethylamino)-9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine (14), had an IC50 = 0.03 microM against serotype 1B, but its activity against 18 other serotypes was not uniform; the IC50s ranged over 260-fold.

9-Benzyl-6-(dimethylamino)-9H-purines with antirhinovirus activity.

A series of 9-benzyl-6-(dimethylamino)-9H-purines and 9-benzyl-2-chloro-6-(dimethylamino)-9H-purines were synthesized and tested in cell culture for activity against rhinovirus type 1B. The 9-benzylpurines that were unsubstituted in the 2-position had weak activity. However, introduction of a 2-chloro substituent resulted in a substantial increase in antiviral activity. One of the most active compounds, 2-chloro-6-(dimethylamino)-9-(4-methylbenzyl)-9H-purine (29), had an IC50 value of 0.08 microM against serotype 1B. Four compounds were tested against 18 other rhinovirus serotypes, but the majority tested were less sensitive than type 1B. The range of serotype sensitivity for 29 varied from 0.08 to 14 microM. These 9-benzyl-2-chloro-9H-purines represent a new class of antiviral agents with in vitro activity against rhinoviruses.

Effect of acyclic pyrimidines related to 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine on herpesviruses.

A series of pyrimidines related to the potent antiherpetic agent 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine (1, BW B759U), all containing the same acyclic chain, have been synthesized. Some of the compounds were derivatives of the naturally occurring bases, cytosine, uracil, and thymine; others included compounds in which the 5-position of the cytosine and uracil moieties were substituted by bromo, iodo, fluoro, methyl, and amino groups. Other variations of the cytosine derivatives were the 5-aza, 2-mercapto, 4-methylamino, 4-dimethylamino, and isocytosine congeners. A 4-aminopyrimidine adduct was also made. Antiviral testing showed that 1-[(1,3-dihydroxy-2-propoxy)methyl]cytosine (18, BW A1117U) was equivalent to the guanine analogue in potency against human cytomegalovirus and Epstein Barr virus. Other compounds in the series were largely inactive in antiviral screening against the herpesviruses.

Purine acyclic nucleosides. 6-Dimethylamino-9-[(2-phenylalanylamido-1-substituted- ethoxy)methyl]purines as candidate antivirals.

Several acyclic puromycin analogues containing hydrocarbon substituents on the 1'-position of the aminoethoxymethyl moiety were synthesized and tested for antiviral activity. The N-carbobenzoxy intermediate 7c was active in vitro against Mengo and Semliki Forest viruses.

Effect of dichloroflavan (BW683C) on the stability and uncoating of rhinovirus type 1B.

Dichloroflavan was found to stabilize rhinovirus 1B to inactivation by heat at 56 degrees C or by acid at pH 4.6 to 5.0. The effects of dichloroflavan, arildone and sodium dodecyl sulphate on uncoating of virus in M.HeLa cells were compared by examining the production of sub-viral particles separated on sucrose density gradients; the development of photoresistance by neutral red labelled virus. All three compounds significantly reduced but did not completely suppress the production of sub-viral particles. They also affected the uncoating of neutral red labelled virus, although dichloroflavan appeared to delay rather than prevent this process. A variant of rhinovirus 1B, isolated by growth in the presence of dichloroflavan, showed increased resistance to inhibition by arildone and SDS as well as dichloroflavan, suggesting a similar site of action for the three compounds.

A novel method for detecting the antiviral activity of flavans in their vapour phase.

This report describes a new method for detecting and measuring the antiviral activity of volatile compounds. This method, the vapour phase test, is a modification of the conventional plaque reduction test, in that the compounds instead of being incorporated in the overlay medium were deposited on the inner surface of the Petri dish lid. During the incubation period, the compounds (if volatile) permeated the overlay medium before exerting their antiviral effect. Compounds which have or may come to clinical trial against rhinovirus infections were compared by normal plaque reduction assays and by means of this new technique. Flavans were shown able to exert their antiviral activity in the vapour phase and thus display an advantage over non-volatile compounds. The report also briefly shows how the technique was used to evaluate the structure-activity relationships in a series of analogous compounds.

3'-Amino-2',3'-dideoxyribonucleosides of some pyrimidines: synthesis and biological activities.

3'-Amino-2',3'-dideoxyribonucleosides of thymine, uracil, and 5-iodouracil (1-3) were synthesized from the corresponding 2'-deoxyribonucleosides via the threo-3'-chloro and the erythro-3'-azido derivatives. Corresponding aminonucleosides of 5-bromouracil, 5-chlorouracil, and 5-fluorouracil (4-6) were synthesized enzymatically with 3'-amino-2',3'-dideoxythymidine as the aminopentosyl donor and thymidine phosphorylase (EC 2.4.2.4) as the catalyst. 3'-Amino-2',3'-dideoxycytidine (7) was synthesized by amination of the 3'-azido precursor of 3'-amino-2',3'-dideoxyuridine. The biological activity of 3'-amino-2',3'-dideoxy-5-fluorouridine (6) was notable among this group of aminonucleosides. It had an ED50 of 10 microM against adenovirus and was not appreciably cytotoxic to mammalian cells in culture. It also had activity against some Gram-positive bacteria but not against a variety of Gram-negative bacteria. The other aminonucleosides (1-5 and 7) lacked or exhibited weak antiviral and antibacterial activities. The only compounds in this group that were appreciably toxic to mammalian cells in culture were the thymidine and deoxycytidine analogues (1 and 7).

Inhibition of an early stage of rhinovirus replication by dichloroflavan (BW683C).

The mechanism of action of a new anti-rhinovirus compound, dichloroflavan, was examined using a variety of techniques. Dichloroflavan was shown to bind to the highly sensitive rhinovirus type 1B (50% inhibitory concentration 0.007 microM) and at a much lower level to the insensitive rhinovirus type 4 (50% inhibitory concentration greater than 25 microM). Binding of the compound to rhinovirus 1B was accompanied by a reduction (about 0.5 log10 units) in virus infectivity which could be restored by treatment with chloroform. Maximum inhibition of virus yield (about 2 log10 units) occurred only when compound and virus were added together, but some inhibition (about 0.7 log10 units) occurred even when the compound was added near the end of a single cycle of replication. This late reduction in infectivity could be abolished by treating with chloroform, and was therefore caused by the compound binding to progeny virus. The compound did not interfere with adsorption of virus to cells, nor with uncoating of the viral RNA. However, little or no viral RNA and protein synthesis occurred in the presence of dichloroflavan provided that the compound was added with the virus. Addition of the compound after virus adsorption had no effect on either viral RNA or protein synthesis. These results indicate that dichloroflavan binds directly to rhinovirus 1B and appears to prevent virus replication at a point immediately after uncoating of the viral RNA.