Novel transformations of gamma-silyl nitro compounds

Introduction of a gamma-silyl group into nitro compounds of dihydrobenzofuran, dihydrobenzo[b]thiophene, and dihydrofuran allowed new transformations to take place in the presence of a Lewis acid to give the corresponding alpha,beta-unsaturated oximes or multisubstituted dihydrofurans, respectively, in good to excellent yields.[reaction: see text]

Design, synthesis, and biological evaluation of novel nucleoside and nucleotide analogues as agents against DNA viruses and/or retroviruses

A novel strategy was developed for the synthesis of N(7)-purine acyclic nucleosides 9 and 14. The key step involved the reaction between [2-(p-methoxyphenyloxy)ethoxy]methyl chloride and N(9)-tritylated nucleobases 6 or 11 followed by concomitant self-detritylation. N(7)-Guanine acyclic nucleoside 9 exhibited antiviral activity, but was phosphorylated by both HSV and Vero cell thymidine kinases. Thus, it showed more potent cellular toxicity than acyclovir (2). N(7)-Adenine acyclic nucleoside 14 was found to be an excellent antiviral agent as well as a good inhibitor of calf mucosal adenosine deaminase. This inhibitory property allows for a greater expression of antiviral activity of antiviral agents, such as N(9)-adenine acyclic nucleoside 1 and ara-A (3). Compound 14 was phosphorylated neither by herpes simplex virus (HSV) thymidine kinase nor by Vero cell thymidine kinase, yet it enhanced the rate constant for the monophosphorylation of acyclovir (2) by HSV thymidine kinase. Consequently, the combination of acyclovir (2) and 14 exhibited greater antiviral activity than acyclovir alone. 7-[2-(Phosphonomethoxy)ethyl]adenine (20) was also synthesized. The key step involved the reaction of 9-(2-cyanoethyl)adenine (15) with methyl iodoacetate in the presence of lithium 2,2,6,6-tetramethylpiperidine in THF. Unlike 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA, 4), the N(7)-isomer 20 was not phosphorylated effectively by 5-phosphoribosyl 1-pyrophosphate synthetase (PRPP synthetase). Thus, it did not exhibit pronounced antiviral activity. Dinucleotide 5'-monophosphate 24 and its butenolide ester 25 were also synthesized. Compound 24 showed substrate activity toward PRPP synthetase and exhibited notable activity against DNA viruses. The antiviral activity of the ester derivative 25 was found to be higher than that of the parent molecule 24. Dinucleotide 5'-monophosphate 24 is susceptible to degradation by snake venom and spleen phosphodiesterases. However, its respective butenolide ester derivative 25 was completely resistant to snake venom and spleen enzymes. Butenolide ester derivatives 28 and 29 were also synthesized and exhibited notable anti-DNA virus and anti-retrovirus activity in vitro. Compounds 2, 4, 9, 14, 20, 24, 25, and 28 were also evaluated for their inhibitory effect on HSV-1-induced mortality in NMRI mice. N(7)-adenine acyclic nucleoside 14 [LD(50) (intraperitoneal, ip) 950 mg/kg], nucleotide-containing butenolide 25 [LD(50) (ip) 675 mg/kg], and butenolide 28 [LD(50) (ip) 710 mg/kg] were found to be potent anti-HSV-1 agents in vivo. In addition, butenolide 28 efficiently decreased tumor formation induced by Moloney murine sarcoma virus (MSV) in NMRI mice while significantly increasing the survival time of MSV-infected mice.

Nickel-catalyzed

Oxabenzonorbornadienes 1 and 2 and azabenzonorbornadiene 3 undergo [2+2] cycloaddition with alkynes (PhC triple bond Ph, PhC triple bond CMe, PhC triple bond CCO2Et, PhC triple bond CCH(OEt)2, and HC triple bond C(CH2)4Me) in the presence of [Ni(PPh3)2Cl2], PPh3, and Zn powder in toluene to afford the corresponding exo-cyclobutene derivatives 4a-e, 5a-e, and 6 in fair to excellent yields. Under similar conditions. EtCO2C triple bond CCO2Et does not react with 1 in toluene to give the [2+2] cycloaddition product, but in acetonitrile, the catalytic [2+2] cycloaddition proceeds and cycloadduct 4 f is isolated in 83% yield. At high temperature, these cyclobutene derivatives readily undergo ring expansion to yield the corresponding 8-membered carbocyclic dienes. Thus, flash vacuum pyrolysis of 4a, 4d, 4f, 6, and 14 at 500 degrees C affords dienes 13a-d and 15 in 70-96% yields. This interesting ring expansion may be viewed as the insertion of an alkyne moiety into the carbon-carbon double bond of a cyclic olefin resulting in the enlargement of the ring by two carbons. Compound 13a is readily deoxygenated by TiCl4 and Zn in THF to give a cyclooctatetraene derivative 16 in 89% yield.

Phototoxicity of some novel porphyrin hybrids against the human leukemic cell line TF-1

Photodynamic induced cytotoxicity by porphyrin-DNA cross linker/intercalator hybrid diads and triads has been studied on the human leukemic cell line TF-1. Cells were incubated for 1 to 4 h with these new photosensitizers and irradiated with white light. Cell survival was assessed by the propidium iodide staining, using flow cytometry analysis. A comparison of the dark and light cell survival factor values suggests that irradiation has a significant effect on the toxicity at low concentrations for the porphyrin-chlorambucil diad and to a lesser extent at high concentrations for the porphyrin-acridone diad, the porphyrin-acridine diad and the porphyrin-cholic acid-chlorambucil triad. While the intrinsic antileukemic (via DNA cross-linking) activity of the chlorambucil moiety and the structural details may be responsible for the photoenhancement of the toxicity, the presence of acridine or acridone which are avid intercalators of DNA, is responsible for a similar effect seen for diads.