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]

Interaction between 3-(p-tolylamino)-1,5-azulenequinone and the deoxyguanosine residue in various oligonucleotides upon photolysis

Eight single-stranded oligodeoxyribonucleotides 32P-labeled at the 5'-end were synthesized; they were annealed with the complementary oligodeoxyribonucleotides to form the corresponding double-stranded helices. These duplexes possessed standard Watson-Crick base pairs, locally perturbed sites of a base mismatch, or a bulge. Further, 5'-32P-labeled oligodeoxyribonucleotides with a hairpin loop were also synthesized. Cleavage of these single- and double-stranded oligodexyribonucleotides selectively at the deoxyguanosine residue was accomplished by use of 3-(p-tolylamino)-1,5-azulenequinone 1 upon irradiation with 350 nm UV light. The single strands were cleaved more efficiently than the double-helices. For the helices containing a deoxyguanosine residue at a bulge, at a hairpin loop or toward the end, the cleaving efficiency was increased. Computation results indicate that two possibilities exist for agent 1 to form two "Watson-Crick type" hydrogen bonds with guanine in single-stranded oligodeoxyribonucleotides; yet, only one possibility exists in duplexes.

Self-sensitized photooxygenation of 3,4-dialkoxyfurans to vitamin C or its derivatives

Self-sensitized photooxygenation of 3,4-dialkoxyfurans 3a-d with molecular oxygen and UV- or sunlight at room temperature gave vitamin C derivatives 2a-d in good to excellent yields. Furan 3c, having photodegradable protecting groups, was also photooxygenated to give L-ascorbic acid (1) in a "one-pot" reaction. Furthermore, a novel photolytic transformation was developed for deuteration of furan 3b at the C-2 position with D(2)O to give furan 3d in 95% yield. Toxicity of furans 3a-c and butenolides 2a-c against human embryonic cell, murine embryo fibroblasts, normal fibroblasts, HeLa, and Vero cell lines in the presence of oxygen and indirect solar light was found to be much less than those of the antipsoriasis drugs anthralin and 8-methoxypsoralen.

Synthesis and biological evaluation of purine-containing butenolides

6-Chloropurine derivatives of gamma-(Z)-ethylidene-2,3-dimethoxybutenolide 3a, gamma-(Z)-ethylidene-2-methoxy-3-(4-nitro)benzyloxybutenolide 3b, gamma-(Z)-ethylidene-2-(4-nitro)benzyloxy-3-methoxybutenolide 3c, gamma-(Z)-ethylidene-2,3-di(4-nitro)benzyloxybutenolide 3d, and dimethylphosphono-gamma-(Z)-ethylidene-2,3-dimethoxybutenolide 11 as well as the adenine derivative of gamma-(Z)-ethylidene-2,3-dimethoxybutenolide 6 were synthesized. The key steps in the high-yield synthesis of 6 involved hydration/dehydration of the C(4)=C(5) in the precursor 3a. In the presence of NH4OH at elevated temperature, 3a underwent a reverse Michael-type addition with water to produce hydrate 5. At 37 degrees C, 6 was also hydrated in the presence of S-adenosyl-L-homocysteine hydrolase to afford 5. Butenolide 6 exhibited an inhibitory property toward the enzyme. Such type II (enzyme-mediated addition of water across C(4)=C(5)) mechanism is the first example of "enzyme-substrate intermediate" inactivation of S-adenosyl-L-homocysteine hydrolase. In contrast with type I mechanism-based inactivation, reduction of enzyme-bound NADP(+) to NADPH was not observed. Upon treatment with HCl, stereoselective dehydration of 5 occurred to give the target molecule 6. At ambident temperature, 3a was hydrated in the presence of NH4OH or pig liver esterase to produce 6-chloropurine derivative 4. An unambiguous proof of the structures of 3-5 was obtained by X-ray crystallographic analysis. For the synthesis of phosphonate derivative 11, the key step involved chlorination of phosphonate 9 by use of CF3SO2Cl and 1,8-diazabicyclo[5.4.0]undec-7-ene in CH2Cl2. 6-Chloropurine-containing butenolide 3d, 6-chloropurine derivative of 4-hydroxybutenolide 4, and adenine-containing 4-hydroxybutenolide 5 did not show anticancer and antiviral activities. 6-Chloropurine-containing ethylidene-2,3-dialkoxybutenolides 3a-c and phosphonate 11, however, exhibited inhibitory activity against murine leukemias (L1210 and P388), breast carcinoma (MCF7), and human T-lymphoblasts (Molt4/C8 and CEM/0) cell lines. They were also notably active toward thymidine kinase-deficient varicella-zoster virus (TK(-)VZV). Adenine-containing ethylidene-2,3-dimethoxybutenolide 6 exhibited marked selectivity in cytostatic activity against the murine leukemia (P388) cell line.

Enthalpy and enzyme activity of modified histidine residues of adenosine deaminase and diethyl pyrocarbonate complexes

Kinetic and thermodynamic studies have been made on the effect of diethyl pyrocarbonate as a histidine modifier on the active site of adenosine deaminase in 50 mM sodium phosphate buffer pH 6.8, at 27 degrees C using UV spectrophotometry and isothermal titration calorimetry (ITC). Inactivation of adenosine deaminase by diethyl pyrocarbonate is correlated with modification of histidyl residues. The number of modified histidine residues complexed to active site of adenosine deaminase are equivalent to 4. The number and energy of histidine binding sets are determined by enthalpy curve, which represents triple stages. These stages are composed of 3,1 and 1 sites of histidyl modified residues at diethyl pyrocarbonate concentrations, 0.63, 1.8, 3.3 mM. The heat contents corresponding to the first, second and third sets are found to be 18000, 22000 and 21900 kJ mol(-1) respectively.

Syntheses of new isodethiaazacephems as potent antibacterial agents

New isodethiaazacephems (+/-)-3, (+/-)-4, and (+/-)-10 as well as the 4-sulfonylated isodethiaazacepham (+/-)-5 were synthesized by chemical methods and found to possess biological activity against five pathogenic microorganisms in vitro. The mesylate and the triflate functionalities in (+/-)-3 and (+/-)-4, acting as effective leaving groups, enhanced remarkably the biological activity in comparison with the parent 3-hydroxyisodethiaazacephem (+/-)-10. The mode of action related to (+/-)-3 and (+/-)-4 can be explained by a [1,4]-elimination process.

Antiviral activities of methylated nordihydroguaiaretic acids. 2. Targeting herpes simplex virus replication by the mutation insensitive transcription inhibitor tetra-O-methyl-NDGA

We had previously reported that tetramethyl-O-NGDA (M4N), a synthetic derivative of the naturally occurring nordihydroguaiaretic acid (NDGA), is able to inhibit HIV Tat transactivation by blocking host Sp1 protein at the Sp1 cognate binding site on the HIV LTR promoter. The present studies were undertaken to examine whether M4N is able to inhibit the replication of herpes simplex virus (HSV), another Sp1-regulated virus. The results showed that in Vero cells, M4N inhibits at micromolar levels (IC50 = 43.5 microM) the expression of the herpes immediate early gene (alpha-ICP4), which is essential for HSV replication. An electrophoretic mobility shift assay, examining Sp1 binding to the alpha-ICP4 promoter, showed a significant inhibition of the control bands: 88% inhibition of the fast moving band (FMB) and 45% of the slow moving band (SMB), at 100 microM of drug concentration. Comparative studies between M4N and acycloguanosine (acyclovir, ACV) in cultured Vero cells revealed an interesting pattern in the drug sensitivity (IC50) and cytotoxicity (TC50) parameters. For M4N, the IC50 varied between 11.7 and 4 microM in 10 passages of HSV-1 and 4 passages of HSV-2 with no indication for a requirement of higher drug concentration. In contrast, for acyclovir, the IC50 increased from 7 microM in the first passage to 444 microM in the tenth passage of HSV-1, and >88 microM for the fourth passage of HSV-2, indicating a rapid build-up of drug resistance against acyclovir. While the selective index (SI), defined as the ratio: TC50/IC50, remained relatively constant for M4N; it dropped 60-fold for acyclovir in the endpoints of viral passages. Drug sensitivity for M4N toward the acyclovir-sensitive strain (sm44) and the acyclovir-resistant strain (ACV-10) of HSV-1 was similar, indicating no cross-resistance between M4N and acyclovir in their anti-HSV effects. These results may have an important clinical relevance since HSV has been shown to be a factor for spreading of HIV.

Antiviral activities of methylated nordihydroguaiaretic acids. 1. Synthesis, structure identification, and inhibition of tat-regulated HIV transactivation

Nordihydroguaiaretic acid (NDGA, meso-1) possesses four phenolic hydroxyl groups. Treatment of NDGA with 0.50-4.1 equiv of dimethyl sulfate and 3.0-6.0 equiv of potassium carbonate in acetone at 56 degrees C gave nine methylated products. Eight of those mono-, di-, tri-, and tetra-O-methylated NDGAs were isolated in pure form, and their structures were identified unambiguously by spectroscopic methods. A preparative amount of tetramethyl NDGA M4N (10) was obtained in 99% yield from NDGA by use of 4.1 equiv of dimethyl sulfate for the methylation. Among the eight different methylated NDGAs (2-6 and 8-10), tetra-O-methyl-NDGA (10) showed the strongest anti-HIV activity (IC50 11 microM). Chemically synthesized 3'-O-methyl-NDGA ((+/-)-2) showed identical anti-HIV activity (IC50 25 microM) to the lignan isolated from Creosote Bush. Lignans with methylated catecholic hydroxyl groups can be produced in large quantities with low cost. At drug concentrations below 30 microM tetramethyl NDGA (10) was a stronger anti-HIV agent than mono- and dimethylated NDGAs.

Cephalosporin 3'-phloroglucide esters and 7-(phloroglucidamido) cephalosporins as novel antibacterial agents

Two series of new phloroglucide derivatives were synthesized that possessed antibacterial activities. The first series includes cephalosporin 3'-phloroglucide esters 19 and 20, which were obtained by condensation of cephalosporin 16 with bioactive phloroglucides 14 and 15, respectively. They exhibited a dual mode of antibacterial action. In comparison with cephalosporins 26 and 27, bearing an acetoxy unit at the C-3' position, the bifunctional cephalosporins 19 and 20 showed a broadened spectrum of activity. Results from the consistent valence force field (CVFF) calculations indicate that the most stable conformational isomer of phenolic acid 14, holding a cis-syn-syn geometry, possessed a cavity. It provides an ideal environment to accommodate metal ions of holoenzymes. Phenolic keto acid 15, however, possessed a trans-anti-syn conformation, which allowed chelation between metal ions and the phenolic hydroxyl groups as well as the carbonyl functionalities. Our biological results show that the cavity formed in phloroglucides plays an important role. The second series includes 7-(phloroglucidamido)cephalosporins 24 and 25, which were synthesized by condensation of cephalosporin 21 with 14 and 15, respectively. Results from the CVFF calculations indicate that cephalosporin 24 also possessed a cavity. Unlike cephalosporin 3'-phloroglucide esters 19 and 20, cephalosporins 24 and 25 were found resistant to beta-lactamases from Staphylococcus aureus 95 and Pseudomonas aeruginosa 18S-H. These new compounds, however, showed notable activities against S. aureus FDA 209P, S. aureus 95, Candida albicans, P. aeruginosa 1101-75, and P. aeruginosa 18S-H.

Synthesis and biological evaluation of an electronically activated isooxacephem

New isooxacephem (+/-)-3-ethyl 2-hydrogen (6RS,7RS)-8-oxo-7-(phenylacetamido)-4-oxa-1-azabicyclo [4.2.0]oct-2-ene-2, 3-dicarboxylate (8) was synthesized from (+/-)-dibenzyl 2-[cis-2-oxo-3-(phenylacetamido)-4-styryl-1-azetidinyl]-2-[t- butyldimethylsiloxy(methoxycarbonyl)methyl]malonate (1) in six steps. This bicyclic beta-lactam was found to possess notable biological activities against several pathogenic microorganisms in vitro, including Staphylococcus aureus 95, S. aureus FDA 209P, Escherichia coli ATCC 39188, Salmonella typhi O-901, Pseudomonas aeruginosa 18S-H, P. aeruginosa 1101-75, and Klebsiella pneumoniae NCTC 418. The electronic activation of the beta-lactam moiety by an ester group plays a prominent role in the biological activity of this novel isooxacephem.

Design, synthesis, and structure-activity relationship of novel dinucleotide analogs as agents against herpes and human immunodeficiency viruses

A new acyclic nucleoside phosphonate (13) containing an adenine moiety was synthesized, which acted as an excellent inhibitor of calf mucosal adenosine deaminase. This inhibitory property allows it to exert great synergistic effect on certain antiviral agents (e.g., ara-A, 37). Phosphonate 13 was not phosphorylated by the bovine brain guanylate kinase nor by 5-phosphoribosyl 1-pyrophosphate synthetase. Syntheses of biologically active nucleotide phosphonate 40 and its phosphonoamidate derivative 42 were accomplished, which showed remarkable activity against herpes viruses and exhibited low host cell toxicity. 3'-Azido-nucleoside phosphonate 20 and 3'-fluoronucleoside phosphonate 32, as well as the corresponding dinucleotide analogs 47 and 48, and their respective phosphonoamidates 53-56 were also synthesized as new compounds, among which phosphonoamidates 53-56 showed potent activity against human immunodeficiency virus. Phosphonoamidates 55 and 56 bearing a methyl D-alaninate moiety exhibited less cellular toxicity than 53 and 54 bearing a methyl L-alaninate moiety. Nucleotide phosphonate 40 as well as dinucleotide phosphonates 47 and 48 were found susceptible to degradation by phosphodiesterases. Their respective phosphonoamidates 42 and 53-56, however, were completely resistant to snake venom and spleen enzymes.

Instrumentation and separation results of medium pressure liquid chromatography

This paper describes the assembly, usage, operation, and separation results of a medium pressure liquid chromatography (MPLC) instrument. Its ability to separate compounds with high resolution makes it a powerful tool for many chemistry laboratories. This equipment can be easily built from inexpensive commercially available materials. Due to the constant reuse of packing materials and infrequent maintenance, MPLC provides a simple, reliable, and economical means of purification.