Activity of acyclic halogenated tubercidin analogs against human cytomegalovirus and in uninfected cells

Pyrrolo[2,3-d]pyrimidine (7-deazapurine) as a privileged scaffold in design of antitumor and antiviral nucleosides

7-Deazapurine (pyrrolo[2,3-d]pyrimidine) nucleosides are important analogues of biogenic purine nucleosides with diverse biological activities. Replacement of the N7 atom with a carbon atom makes the five-membered ring more electron rich and brings a possibility of attaching additional substituents at the C7 position. This often leads to derivatives with increased base-pairing in DNA or RNA or better binding to enzymes. Several types of 7-deazapurine nucleosides with potent cytostatic or cytotoxic effects have been identified. The most promising are 7-hetaryl-7-deazaadenosines, which are activated in cancer cells by phosphorylation and get incorporated both to RNA (causing inhibition of proteosynthesis) and to DNA (causing DNA damage). Mechanism of action of other types of cytostatic nucleosides, 6-hetaryl-7-deazapurine and thieno-fused deazapurine ribonucleosides, is not yet known. Many 7-deazaadenosine derivatives are potent inhibitors of adenosine kinases. Many types of sugar-modified derivatives of 7-deazapurine nucleosides are also strong antivirals. Most important are 2'-C-methylribo- or 2'-C-methyl-2'-fluororibonucleosides with anti-HCV activities (several compounds underwent clinical trials). Some underexplored areas of potential interest are also outlined.

Synthesis of Non-Nucleosides: 7- and 1,3-Substituents of New Pyrrolo[2,3-d]pyrimidin-4-ones on Antiviral Activity

A series of non-nucleosides 9-47 were synthesized. Compounds 1-4 were reacted with formic acid (85%) to afford compounds 5-8. Then, the latter compounds were reacted with alkyl halides a-f (2-bromopropane, 2-bromobutane, benzyl bromide, benzyl chloromethyl ether, chloromethyl ethyl ether, phenacyl bromide) in the presence of NaH in dry DMF to give the desired compounds 9-47, which were evaluated for activity against herpes simplex virus type-II (HSV-II).

Synthesis and biological activity of 5-fluorotubercidin

The electrophilic fluorination of 4-chloropyrrolo[2,3-d]pyrimidine (1) was studied culminating a 59% conversion of compound 1 to 4-chloro-5-fluoropyrrolo[2,3-d]pyrimidine (2) using Selectfluor. This transformation proceeded via the 4-chloro-5,6-dihydro-5-fluoro-6-hydroxypyrrolo[2,3-d]pyrimidine (3) in a 9:1 trans:cis ratio. The trans isomer of compound 3 was studied by 1H NMR and 19F NMR, and the 5-H tautomer (4) was observed as another intermediate. A modified Vorbruggen procedure of compound 2 and tetra-O-acetylribose gave 4-chloro-5-fluoro-7-(2,3,5,-tri-O-benzoyl-beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine (6) in a 65% yield. Treatment of compound 6 with ammonia (l) in dioxane gave 5-fluorotubercidin (7). No antibacterial activity was observed. An MTT assay (Promega) against Huh-7 liver cells, normal mouse spleen cells stimulated with Con A (a T-cell mitogen), and normal mouse spleen stimulated with LPS (a B-cell mitogen) showed no significant toxicity. Increased activity of 7 over tubercidin was observed against L-1210 cells and toxicity in fibroblast cells was reduced.

Application of flow cytometry to determine the cytotoxicity of urethane dimethacrylate in human cells

The effects of an oligomer, urethane dimethacrylate (UDMA), on two human cell lines were studied using flow cytometry (FCM). Untreated and treated cultures of propidium iodine-stained KB (epidermal oral carcinoma cells) and human foreskin fibroblast (HFF) cells were analyzed for cellular DNA content. Concentrations of 10 and 25 microM of UDMA slightly perturbed the KB cell cycle progression at 24 and 48 h of incubation. However, the effect of 50 microM was more pronounced at the latter incubation time period. In cell growth experiments, the sublethal concentrations (10 and 25 microM) produced inhibition of KB cell growth rate at a moderate level, which resulted in the prolongation of cell population doubling time. Significant inhibition of cell growth occurred when 50 microM (lethal concentration) was used. Data obtained from the cell cycle perturbation analysis, evidenced by FCM, correlated with the extent of inhibition in KB cell growth rates. The effects of sublethal concentrations were reversible during a 24 h period of oligomer withdrawal from culture medium. In contrast, the effects of 50 microM were not reversible. In HFF cells the depletion of S phase in the cell cycle was the major effect of 50 microM of UDMA. It was concluded that FCM technology is an ideal and practical approach for studying the cytotoxicity of components of dental composites.

Improved synthesis and biological evaluation of an acyclic thiosangivamycin active against human cytomegalovirus

We previously described the synthesis and in vitro antiviral activity of an acyclic thiosangivamycin analog (Gupta et al., 1989a). In order to extend these initial studies, a new, multi-gram synthesis of 4-amino-7-[(2-hydroxy- ethoxy)methyl]pyrrolo]2,3-d]pyrimidine-5-thiocarboxamide (compound 229) was achieved in 5 steps from the known 5-amino-2-bromo-3,4-dicyanopyrrole in good overall yield. In plaque reduction assays with HCMV, compound 229 had an IC50 of 7 microM; in yield reduction assays the IC90 was 25 microM. The compound was less active against MCMV, HSV-1, HSV-2, and least active against VZV. Concentrations of compound 229 up to 32 microM did not affect the growth of KB cells for incubation periods up to 72 h. At 100 microM, a prolongation in population doubling time from 21 h (untreated) to 35 h was noted. This inhibition, however, was reversible upon removal of the compound suggesting the inhibition was cytostatic rather than cytotoxic. Flow cytometric studies with compound 229 in HFF cells revealed an accumulation of cells in S phase and a concurrent loss of cells in G2/M phase, suggesting an early S phase blockage. We conclude there is adequate separation between antiviral activity and cytotoxicity to merit further work with this class of pyrrolopyrimidines.