Synthesis of Optically Pure (R)-4a-Methyl-4,4a,5,6,7,8-hexahydro-2(3H)-naphthalenone and Its Transformation into (+)-7-Hydroxycostal

A novel synthesis of the enone 12 starting from (+)-dihydrocarvone (3) and its transformation into (+)-7-hydroxycostal (1) are described. The ketone 10, obtained from 4 through a four-step sequence was converted to 12 by acid-catalyzed elimination and subsequent regioselective hydrogenation. Alternatively, the methoxyhydroperoxide 13 generated by the ozonolysis of 4 was subjected to the Criegee rearrangement, providing a mixture of 10 and 14, which on acid treatment, gave 11. Transformation of 12 into 19 was accomplished via a five-step reaction sequence. The reaction of 19 with the lithium alkoxide of 2-lithio-2-propenol afforded (+)-7-hydroxycostol (2), whose oxidation with manganese dioxide gave rise to (+)-7-hydroxycostal (1).     

Synthesis of (±)-Muscone from Ethyl 6-Methyl-8-oxopentadecanedioate

(±)-Muscone (3-methylcyclopentadecanone) (8) was synthesized from ethyl 6-methyl-8-oxopentadecanedioate (1) in a 31.9% over-all yield. Ethylene ketal (2) of 1 was cyclized to the acyloin mixture (3) by the acyloin condensation. Reduction of 3 gave 9,9-ethylenedioxy-7-methylcyclopentadecane-1,2-diol (4) which afforded 1,2-ditosyloxy derivative (5). By detosylation according to the Tipson-Cohen procedure, 5 was converted to 9,9-ethylenedioxy-7-methylcyclopentadec-1-ene (6) which was hydrogenated to 8.     

Conferin,potent antioxidant and anti-inflammatory isoflavone from Caragana conferta Benth

Conferin (1), a new isoflavone, has been isolated from the ethyl acetate soluble fraction of Caragana conferta Benth. along with seven known compounds, namely biochanin A (2), p-hydroxybenzoic acid (3), 3,5- dimethoxybenzoic acid (4), ursolic acid (5), erythrodiol (6), pinoresinol (7), and syringresinol (8), reported for the first time from this species. The structure of the new isoflavone was deduced on the basis of spectroscopic studies. Compounds 1 and 2 were investigated for biological activities and showed significant anti-inflammatory activity in carrageenan induced paw edema of rats. Evaluation of antioxidant activity by the radical scavenging method indicated that compound 1 is a potent antioxidant while 2 is moderately active. It was also shown that the reducing capability of compound 2 was remarkably increased in a concentration dependent manner as compared to 1. Compound 1 showed moderate inhibitory activity against the enzyme lipoxygenase, while 2 showed weak activity.     

Oligomerization of N-Tosylindole with Aluminum Chloride

The reactivity of N-tosylindole (4) in the presence of aluminum chloride was studied, and two types of oligomerization of 4 were observed. One type was condensation between both pyrrole parts (dimers 5 and 6 and trimer 7) and the other was between a pyrrole part and a benzene part of each indole nucleus (dimers 8 and 9).     

Synthesis of L-3′-Hydroxymethylribonucleosides

Abstract

The target compounds were synthesized via the key intermediate carbohydrate 8, which was synthesized by first selectively protecting the 1′ - and 2′- hydroxyl groups followed by selective tosylation of the 5′ -hydroxyl group to obtain compound 3. The tosyl moiety was then replaced by a benzyl ether to obtain 4. Compound 4 underwent Dess-Martin oxidation to afford the ketone 5. Compound 5 was subjected to Wittig olefination to afford the alkene 6 followed by regioselective hydroboration to obtain 7. Compound 7 was fully acetylated using acetic acid, acetic anhydride and sulfuric acid to obtain the key intermediate 8.     

Synthesis of new uracil derivatives and their sugar hydrazones with potent antimicrobial,antioxidant and anticancer activities

Abstract

6-(4-Chloro-3-nitrophenyl)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile (4) was prepared and was reacted with ethyl chloroacetate, hydrazine hydrate, 4-chloroaniline, formaldehyde, acetic anhydride, formic acid, carbon disulfide, 4-cyanobenzaldehyde, triethyl orthoformate, D-sugars, 4-aminoacetophenone, benzoyl choride and cyclohexanone to afford a series of new uracil derivatives (5–18). Examination of some of the prepared compounds for their antimicrobial, antioxidant and anticancer activities was conducted. Among the tested samples, compound 17 was the most active substance against the gram-positive bacteria and was more potent than the reference drug Cefoperazone. Moreover, the antibacterial activity of 17 was higher against gram-negative bacteria. Compounds 6 and 13 reached a higher scavenging ability toward DPPH radicals and are better candidates for antioxidant activity. Also, compounds 6 and 13 had no significant anticancer activity toward liver cancer (Hep G2) and breast cancer (MCF-7) cell lines.     

Synthesis and DNA Binding Properties of a New Benzo[f]Imidazo[1,5b]-Isoquinoline-Butan-1,2-Diol Derivative

A benzo[f]imidazo[1,5b]-isoquinoline derivative 4 with a 1,2-butandiol linker was prepared by reaction of a trimethylsilylated 5-naphthylidenehydantoin 3 with a 2,3-dideoxy-D-glycero-pentafuranoside 2 in 22% yield. After deprotection, the resulting compound 5 was converted to a DMT protected phosphoramidite building block 7 for standard DNA synthesis. DNA/DNA, DNA/RNA duplexes with 5 inserted as bulges were destabilized, except when the new amidite was used for the synthesis of a zipping duplex.     

Nucleotides Part LXXX: Synthesis of 3′-O Fluorescence Labeled Thymidine Derivatives and Their 5′-O-Triphosphates

A new labeling technique attaching a fluorescent pteridine derivative (3, 5) via a linker onto the 3′-OH group of 5′-O-dimethoxytritylthymidine (7) was developed to lead to the conjugates 8 and 11. After detritylation to give 9 and 12, the final conversion into the corresponding 5′-triphosphates (13, 14), which were isolated as sodium salts, was performed by known methods.     

Nucleosides. 140. Stereoselectivity of the Reaction of 1-(2,3-Anhydro-5-O-Benzoyl-β-D-Lyxofuranosyl) Uracil with Ammonium Azide. Isolation and Characterization of 2-Azido-Xylo-Nucleoside Derivatives

Abstract

The composition of the products of reaction of 1-(2,3-anhydro-5-O-benzoyl-β-D-lyxofuranosyl)uracil (1) with NH₄N₃ was studied by a reverse-phase HPLC system which was found to separate the 3-azido-arabino 2 and 2-azido-xylo 3 isomers that were formed. The use of a 10:1 ratio of NH ₄ N ₃ to 1 in refluxing EtOH was found to minimize ring opening at C-2 (7%). The higher stereoselectivity of ring opening produced by using a large excess of NH ₄ N ₃ was suppressed by conducting the reaction in DMF. Preventing the escape of the NH ₃ by-product only resulted in debenzoylation. The isolation of pure, crystalline 3 was achieved by reverse-phase preparative HPLC. Separation from the arabino isomer was also effected by debenzoylation and selective acetonide formation with the xylo isomer, which allowed facile isolation of the latter by normal phase chromatography. Hydrolysis of the acetonide 7 provided unprotected 2-azido-xylo nucleoside 6, which was also obtained by NaOMe treatment of 3. The mechanistic basis for the stereoselectivity of epoxide opening is discussed.     

New Neplanocin Analogues. V. A Potent Adenosylhomocysteine Hydrolase Inhibitor Lacking Antiviral Activity. Synthesis And Antiviral Activity Of 6″-Carboxylic Acid Derivatives Of Neplanocin A 1

Abstract

The 6′-carboxylic acid derivative of neplanocin A 3 was synthesized from NPA, and was converted to the corresponding methyl ester 4 and amides 5 and 6. These were evaluated for their anti-RNA-virus activities. Of the derivatives synthesized, only 5 was active against RNA viruses within the concentration range of 0.14-4.88 μg/mL. Compounds 3 and 5 showed a potent inhibitory effect on S-adenosylhomocysteine (AdoHcy) hydrolase from rabbit erythrocytes. Although a close correlation between the inhibitory effect of adenosine analogues on AdoHcy hydrolase and their antiviral potency has been demonstrated, 3 did not show any anti-RNA-virus activities.

     

Nucleosides and Nucleotides. 192. Toward the Total Synthesis of Cyclic ADP-Carbocyclic-Ribose. Formation of the Intramolecular Pyrophosphate Linkage by a Conformation-Restriction Strategy in a Syn-form Using a Halogen Substitution at the 8-Position of the Adenine Ring

Abstract

The synthesis of cyclic ADP-carbocyclic-ribose (2), as a stable mimic for cyclic ADP-ribose, was investigated. Construction of the 18-membered backbone structure was successfully achieved by condensation of the two phosphate groups of 19, possibly due to restriction of the conformation of the substrate in a syn-form using an 8-chloro substituent at the adenine moiety. SN2 reactions between an optically active carbocyclic unit 8, which was constructed by a previously developed method, and 8-bromo-N ⁶-trichloroacetyl-2′,3′-O-isopropylideneadenosine 9c gave N-1-carbocyclic derivative, which was deprotected to give 5′,5′-diol derivatives 18. When 18 was treated with POCl₃ in PO(OEt)₃, the bromo group at the 8-position was replaced to give N-1-carbocyclic-8-chloroadenosine 5′,5′-diphosphate derivative 19 in 43% yield. Treatment of 19 with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride gave the desired intramolecular condensation product 20 in 10% yield. This is the first chemical construction of the 18-membered backbone structure containing an intramolecular pyrophosphate linkage of a cADPR-related compound with an adenine base.     

Periodicity of DNA in exons

Background  

The periodic pattern of DNA in exons is a known phenomenon. It was suggested that one of the initial causes of periodicity could be the universal (RNY) _n pattern (R = A or G, Y = C or U, N = any base) of ancient RNA. Two major questions were addressed in this paper. Firstly, the cause of DNA periodicity, which was investigated by comparisons between real and simulated coding sequences. Secondly, quantification of DNA periodicity was made using an evolutionary algorithm, which was not previously used for such purposes.     

Stereoselective Synthesis of Some 3-Nitroglucopyranosyladenine Analogues via a Nitroolefin: Intermediate as Potential Therapeutic Agents

Abstract

Three isomers of 9-(4,6-O-benzylidene-3-deoxy-β-D-hexopyranosyl) adenines (2–4) were isolated. The manno isomer 2 could be isomerized to the gluco isomer 3. The manno (2) and galacto isomer (4) were deprotected to 5 and 7, respectively. Michael addition of some organic amines and thiolates to the nitroolefin intermediate (8) gave the corresponding 2-(substituted)-3-nitro-glucopyranosides (9a-h). Compounds 9a,c,h were deprotected to 10a,c,h. Sodium azide with 8 gave the triazolo nucleoside 11, which was deprotected to 12. 2-Deoxy-3-nitro analogue 14 was also obtained.

     

Community Structure,Geochemical Characteristics and Mineralogy of a Hypersaline Microbial Mat,Cabo Rojo,PR

Seasonal variations in precipitation changed the community composition and microbial activity in a hypersaline, tropical microbial mat, in Cabo Rojo, PR. Using a combination of dissection, light, and transmission electron microscopy, terminal restriction fragment length polymorphism (T-RFLP), in situ microelectrode studies, and ³⁵ S isotope incubations, we documented the major differences between wet and dry seasons. During the wet season (precipitation 177 mm), cyanobacterial (green layer) and anoxyphototrophic (pink layer) communities, as well as the black FeS layer were well-developed, and T-RFLP patterns indicated a diverse community. The rate of oxygenic photosynthesis was 49 μ M min ^{? 1} . Aerobic respiration was 29 μ M min ^{? 1} , and sulfate reduction was 264 nmol cm ^{? 3} h ^{? 1} . During the dry season (precipitation 51 mm), cyanobacteria and anoxyphototrophs were less diverse and abundant, and T-RFLP patterns were less complex. The O ₂ production rate was reduced to 9 μ M min ^{? 1} , as was O ₂ consumption (7 μ M min ^{? 1} ) and sulfate reduction (26 nmol cm ^{? 3} h ^{? 1} ). Aragonite, calcite, halite, and quartz were the predominant minerals. Seasonal differences were found in the green and pink layers for both halite and quartz. Gypsum was not observed, likely due to a sample handling artifact. The fluctuations in community composition and metabolic activity, principally reflected in fluctuations in binding and trapping potential of the uppermost mat community, might be responsible for the observed differences in mineralogy.     

Tandem photoaffinity labeling of a target protein using a linker with biotin,alkyne and benzophenone groups and a bioactive small molecule with an azide group

A novel linker containing biotin, alkyne and benzophenone groups (1) was synthesized to identify target proteins using a small molecule probe. This small molecule probe contains an azide group (azide probe) that reacts with an alkyne in 1 via an azide–alkyne Huisgen cycloaddition. Cross-linking of benzophenone to the target protein formed a covalently bound complex consisting of the azide probe and the target protein via 1. The biotin was utilized via biotin–avidin binding to identify the cross-linked complex. To evaluate the effectiveness of 1, it was applied in a model system using an allene oxide synthase (AOS) from the model moss Physcomitrella patens (PpAOS1) and an AOS inhibitor that contained azide group (3). The cross-linked complex consisting of PpAOS1, 1 and 3 was resolved via SDS–PAGE and visualized using a chemiluminescent system. The method that was developed in this study enables the effective identification of target proteins.     

Synthesis and characterization of poly-O-methyl-[n]-polyurethane from a d-glucamine-based monomer

Aminoalditol 1-amino-1-deoxy-d-sorbitol (1) was readily converted into 2,3,4,5-tetra-O-methyl derivative 5, a key precursor of a sugar-based [n]-polyurethane. For the polymerization, the free amino or primary hydroxyl groups of 5 were selectively activated and employed as starting monomers in two alternative procedures. Thus, the amino function of 5 was converted into the isocyanate derivative by treatment with di-tert-butyltricarbonate, and polymerized in situ in the presence of Zr(IV) acetylacetonate. The resulting poly(1-amino-1-deoxy-2,3,4,5-tetra-O-methyl-d-sorbitol)urethane (8) had a moderate molecular weight and showed the presence of urea units. The alternative synthesis of 8 involved the activation of the free hydroxyl group of 5 as the corresponding phenylcarbonate. The polymerization of this α-amino-ω-phenylcarbonate alditol monomer does not require a metal catalyst. The resulting material exhibited an improved molecular weight and higher purity than that obtained via the isocyanate. [n]-polyurethane 8 was highly soluble in water as well as in common organic solvents (chloroform, acetone, ethyl acetate, etc) and was obtained as an amorphous material which was characterized thermally and spectroscopically.     

Reaction of Retinol with Peroxynitrite

The reactivity of retinol with peroxynitrite, which is a strong oxidant and has been reported to induce several biological damages, was investigated. 13-cis-14-nitroretinol (1), 13-trans-14-nitroretinol (2), 13-apo-β-carotenone (3), retinal (4), 11,14-epoxyretinol (5), and 11,15-epoxyretinol (6) were identified as reaction products of retinol with peroxynitrite. From these results, it was observed that retinol can undergo a nitration reaction with peroxynitrite. Furthermore, the formation mechanisms of 1, 2, and 3 from retinol with peroxynitrite are discussed.     

Synthesis and Enantioselectivity of Cyclopropavir Phosphates for Cellular GMP Kinase

Enantiomeric cyclopropavir phosphates (+)-9 and (?)-9 were synthesized and investigated as substrates for GMP kinase. N²-Isobutyryl-di-O-acetylcyclopropavir (11) was converted to (+)-monoacetate 12 using hydrolysis catalyzed by porcine liver esterase. Phosphorylation via phosphite 13 gave after deacylation, phosphate (+)-9. Acid-catalyzed tetrahydropyranylation of (+)-monoacetate 12 gave, after deacylation, tetrahydropyranyl derivative 14. Phosphorylation via phosphite 15 furnished, after deprotection, enantiomeric phosphate (-)-9. Racemic diphosphate 16 was also synthesized. The phosphate (+)-9 is a relatively good substrate for GMP kinase with a K_M value of 57 μM that is similar to that of the natural substrates GMP (61 μM) and dGMP (82 μM). In contrast, the enantiomer (?)-9 is not a good substrate (K_M 1200 μM) indicating a significant enantioselectivity for the GMP kinase catalyzed reaction of monophosphate to diphosphate.     

Inhibition of Real-Time PCR in DNA Extracts from Aquifer Sediment

Variation in inhibition of real-time PCR was investigated with DNA extracts from 50 aquifer sediment core samples of 5 cm length collected through a 2.5 meter vertical profile across a landfill leachate plume. The inhibition was quantified using an internal control of the green fluorescent protein ( gfp ) gene, which was spiked into the real-time PCR reactions. The inhibition was investigated at two gfp gene concentrations: at 1.7 · 10 ⁷ gfp gene copies/g sediment (5.1 · 10 ⁴ gfp gene copies/PCR reaction) and at 1.7 · 10 ⁵ gfp gene copies/g sediment (5.1 · 10 ² gfp gene copies/PCR reaction). Despite the low TOC content of the sediment (average 0.4 mg C/g dw) the average real-time PCR response was partially inhibited, compared to a reference (pure water), at both high and low gfp concentrations. The relative amplification (reference = 1) was 0.85 ± 0.20 (high) and 0.66 ± 0.23 (low), showing significantly (P < 0.05) stronger inhibition at the lower target gene concentration. The inhibition of the real-time PCR did not show a systematic variation in the vertical profile related to plume position but variations were significant on a small scale of 5–15 cm depth intervals. One of the 50 samples failed to produce a signal with either concentration of the gfp internal control and three other samples inhibited real-time PCR at both high and low gfp concentration. These 4 samples, which were the samples with the highest inhibition, were the only DNA extracts with a visible brown colouration, indicating contents of humic-like substances. Elevated absorbance at 400 nm of these samples also indicated that humic-like substances were responsible for inhibition. However, other factors not associated with either absorbance or TOC may have contributed to the inhibition in less inhibited samples since the variation in real-time PCR response could not be sufficiently explained by absorbance or TOC. The results of this study suggest that an internal control is needed in real-time PCR reactions with DNA from environmental samples due to variation in inhibition to correctly quantify the number of target genes, especially at low target gene concentrations, when dilution of DNA extracts is not practical.     

Novel 1-acyl-4-substituted semicarbazide derivatives of primaquine − synthesis,cytostatic, antiviral and antioxidative studies

A series of novel 1,4-substituted semicarbazides 5a–g with a primaquine moiety bridged by a carbonyl group at position 1 and a cycloalkyl, aryl, benzyloxy or hydroxy substituent at position 4 were prepared and biologically evaluated. The synthetic pathways applied for preparation of the title compounds involved benzotriazole as synthetic auxiliary. Primaquine semicarbazides 5a–g and their synthetic precursors benzotriazolecarbonyl semicarbazides 4 were evaluated for cytostatic, antiviral and antioxidative activities. All compounds of the series 5 showed high selectivity towards MCF-7 cells (breast carcinoma) with IC₅₀ values in the low micromolar range and the most active was benzyl derivative 5c (IC₅₀ 1?±?0.2 µM). The benzhydryl derivative 5e showed significant cytostatic activities towards all the tested cell lines (IC₅₀ 4–18 µM). The same compound was the strongest lipoxygenase inhibitor as well (51%). The highest antioxidant activity was demonstrated for the hydroxy derivative 5g and benzotriazolecarbonyl semicarbazides 4b,c (61.2–68.5%). No antiviral activity was observed against a wide variety of DNA and RNA viruses.