N6-Alkylthiomethyl and N6-Arylthiomethyl Derivatives of Adenosine and Their Cytokinin Activity

Five new derivatives of adenosine, N⁶-[(1-methylethyl)thiomethyl]-(1), N⁶-methyithiomethyl-(2), N⁶-phenylthiomethyl-(3), N⁶-[(3-amino-3-carboxypropyl)thiomethyl]-(4), and N⁶-[(2-amino-2-carboxyethyl)thiomethyl]adenosine (5), were synthesized and their cytokinin activity was tested in the Amaranthus betacyanin assay and the soybean callus growth.

1, 2, and 3 were active in the former assay and all five compounds were active in the latter assay. The activities of the compounds were, however, weaker than those of the reference derivatives, in which Sulfides were replaced by methylenes, N⁶-isopentyl-, N⁶-n-propyl-, N⁶-benzyl-, and N⁶-(5-amino-5-carboxypentyl)adenosine. This fact indicates that the sulfide structure introduced into the N⁶-side chains had the effect of reducing cytokinin activity.     

Production and chitinase-binding ability of lipo-chitopentaose nodulation factor

The penta-N-acetyl-chitopentaose 2 has been prepared by using recombinant E. coli strains harboring the nodC gene (encoding chitooligosaccharide synthase) from Azorhizobium caulinodans. Then, the deacetylase NodB removed the N-acetyl moiety from the nonreducing terminus of 2 to give tetra-N-acetyl-chitopentaose 3. N-Acylation of 3 with stearyl chloride was performed in DMF containing water and provided the corresponding lipo-chitopentaose nodulation factor 4. A binding chitinase assay indicated that 4 was much more stable than 3.     

Production of N 2 O by Ammonia Oxidizing Bacteria at Subfreezing Temperatures as a Model for Assessing the N 2 O Anomalies in the Vostok Ice Core

It was suggested that the abnormally high N ₂ O values found in 130,000–160,000 year-old Vostok ice core samples, characterized by high δ ¹⁵ N and low δ ¹⁸ O values, resulted from in situ microbial N ₂ O production. To substantiate these observations we obtained new geochemical data from the last glacial period and showed the existence of additional small N ₂ O anomalies. To test the hypothesis that microbial metabolism could contribute to these anomalies, we developed protocols for examining the ability of Nitrosomonas cryotolerans cells to produce N ₂ O at subfreezing temperatures. Our results show that these model, frozen cultures produce N ₂ O at temperatures as low as ?32°C.     

An Improved Synthesis of N6-(6-Aminohexyl)FAD

Abstract

We report an improved synthesis of N ⁶-(6-aminohexyl)FAD (1) using an efficient one-pot conversion of inosine to the N-trifluoroacetyl protected N ⁶-(6-aminohexyl)adenosine 3. The 5′-O-phosphorylated AMP derivative 4, activated as the imidazolide, was coupled with commercial sodium riboflavin phosphate by using 18-crown-6 in DMF.     

Synthesis of bis-amino acid derivatives by Suzuki cross-coupling,Michael addition and substitution reactions

Several bis-amino acids were prepared using a bis-Suzuki coupling (compounds 4–8, 10), a sequential Michael addition and bis-Suzuki coupling (compounds 12, 13) and a Michael addition followed by a substitution reaction (compounds 18, 19). Thus, the pure stereoisomer of the methyl esters of N-(tert-butoxycarbonyl)-β-bromodehydroaminobutyric acid and dehydrophenylalanine and of N-benzyloxycarbonyl-β-bromodehydroaminobutyric acid were reacted with 1,4-phenylene-bis-boronic acid or 9,9-dioctyl-9H-fluorene-2,7-bis-boronic acid using modified Suzuki coupling conditions. The corresponding bis-dehydroamino acid derivatives were obtained in good to high yields maintaining the stereochemistry of the starting materials. This reaction was also applied successfully to a brominated dehydrodipeptide and 1,4-phenylene-bis-boronic acid showing that it could be used to create cross-links in peptide chains. An N,N-diacyldehydroalanine derivative was used in a sequential Michael addition and bis-Suzuki coupling giving a p-terphenyl bis-amino acid and a fluorenyl bis-amino acid in good yields. Two bis-α,β-diamino acids were obtained by a Michael addition of 1,2,4-triazole to the methyl esters of N-(4-toluenesulfonyl), N-(tert-butoxycarbonyl) dehydroamino acids followed by treatment with ethylenediamine.     

Regioselective Synthesis of Indazole N 1‐ and N 2‐(β‐d‐Ribonucleosides)

The regioselective synthesis of 4‐nitroindazole N ¹‐ and N ²‐(β‐d‐ribonucleosides) (8, 9, 1b and 2b) is described. The N ¹‐regioisomers are formed under thermodynamic control of the glycosylation reaction [fusion reaction or Silyl Hilbert‐Johnson glycosylation for 48 h (66%)], while the kinetic control (Silyl Hilbert‐Johnson glycosylation for 5 h) afforded only the N ²‐isomer (64%). The structures of the nucleosides 1b and 2b were assigned by single crystal X‐ray analyses. The 4‐amino‐N ¹‐(β‐d‐ribofuranosyl)‐1H‐indazole (3b) was obtained from the nitro nucleoside 1b by catalytic hydrogenation. Compound 3b shows fluorescence while the 4‐nitroindazole nucleosides 1b and 2b do not possess this property.     

Novel achiral titanocene anti-cancer drugs synthesised from bis-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylamino fulvene and lithiated heterocyclic compounds

Abstract From the carbolithiation of 6-bis-N,N-dimethylamino fulvene (3a) and different ortho-lithiated heterocycles (furan, thiophene and N-methylpyrrole), the corresponding lithium cyclopentadienide intermediate (4a–c) was formed. These three lithiated intermediates underwent a transmetallation reaction with TiCl₄ resulting in bis-N,N-dimethylamino-functionalised titanocenes 5a–c. When these titanocenes were tested against LLC-PK cells, the IC₅₀-values obtained were of 240, and 270 μM for titanocenes 5b and 5c, respectively. The most cytotoxic titanocene in this paper, 5a with an IC₅₀-value of 36 μM was found to be approximately six times less cytotoxic than its mono-N,N-dimethylamino substituted analogue Titanocene C (IC₅₀ = 5.5 μM) and almost ten times less cytotoxic than cisplatin, which showed an IC₅₀-value of 3.3 μM, when tested on the LLC-PK cell line. Graphical abstract Bis-(bis- (N,N-dimethylamino)-2-(N′-methylpyrrolyl)methylcyclopentadienyl) titanium (IV) dichloride, {η⁵-C₅H₄-CH[N(CH₃)₂]₂[C₅H₃NCH₃]}₂TiCl₂ was synthesised starting from 6-bis-(N,N-dimethylamino) fulvene and 2-N-methylpyrrolyl lithium. Herein, we present the synthesis and DFT structure of the titanocene and two further derivatives followed by MTT-based cytotoxicity tests on pig kidney epithelial (LLC-PK) cells. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Facile Synthesis of N-(1-Alkenyl) Derivatives of 2,4-Pyrimidinediones

Abstract

N-(1-alkenyl) derivatives of 2,4-pyrimidinediones (6–9) were prepared in a one pot synthesis from aldehydes and the nucleobases using trimethylsilyl trifluoromethanesulfonate (TfOTMS) as coupling reagent. Presilylation of the above nucleobases, and N ⁶-benzoyladenine, with excess N,O-bis(trimethylsilyl)acetamide (BSA) followed by addition of one mol eq. TfOTMS yielded the N-(1-trimethylsilyloxyalkyl) derivatives 1–5.     

Isobutyl Amides from Pepper (Piper nigrum L.)

Four isobutyl amides were isolated from the fruits of white pepper (Piper nigrum L.) and identified to be N-isobutyl-13-(3,4-methylenedioxyphenyl)-2E,4E,12E-tridecatrienamide (3, guineensine), N-isobutyl-2E,4E,8Z-eicosatrienamide (5), N-isobutyl-2E,4E-octadecadienamide (6) and N-isobutyl-2E,4E-decadienamide (7, pellitorine).     

Novel Types of Spin Labelled Nucleoside Analogues

Abstract

A variety of modified nucleosides or dinucleosides bearing one of the following functions have been prepared: N-hydroxyureas, N-hydroxyamines, N-hydroxycarbamates, α-(N-hydroxyamino)phosphonates. Upon oxidation, these compounds afford the corresponding aminoxyl free radicals which have been studied by EPR spectroscopy. Some of these compounds exhibited antiviral properties.     

Asymmetric hydrogenation of dehydrodipeptides bearing different protecting groups

Summary.  N-[(Z)-N-Benzoyl- or N-boc-(2-fluorophenyl)dehydroalanyl]-(R)- or (S)-phenyl-alanines 1,2,5 and 6 were hydrogenated in the presence of chiral and achiral rhodium complexes. The optical induction is compared to the results obtained using the corresponding esters as substrates. Received November 11, 2001 Accepted January 15, 2002     

Interaction of (2′ -5′) and (3′ -5′) Linked 2-Aminoadenylyl-3-aminoadenosines with Polyuridylic Acid

Abstract

2′-5′ and 3′-5′ linked 2-aminoadenylyl-2-aminoadenosines [(2′-5′)n²Apn²A (1) and (3′-5′)n²Apn²A (2)] were synthesized by condensation of 5′-O-monomethoxytrityl-N ² N ⁶-dibenzoyl-2-aminoadenosine and N ²,N ⁶,2′,3′-O-tetrabenzoyl-2-aminoadenosine 5′-phosphate using dicyclohexylcarbodiimide (DCC). The conformational properties of these dimers 1 and 2 were examined by UV, NMR and CD spectroscopy. The results reveal that the 2′-5′-isomer 1 takes a stacked conformation, which contains a larger base-base overlap and is more stable against thermal perturbation with respect to the 3′-5′-isomer 2. Interactions of 1 and 2 with polyuridylic acid (Poly (U)) were also examined by Tm, mixing curves, UV and CD spectra. Both the dinucleoside isomers 1 and 2 formed a complex of 1 : 2 stoichiometry with poly(U), which was much more stable than that of the corresponding ApA isomer     

Synthesis of the Oligoribonucleotides Incorporating 8-Oxo-Guanosine and Evaluation of their Base Pairing Properties

6-O-7-N-Bis(diphenylcarbamoyl)-2-N-phenoxyacetyl-5′-O-dimethoxytrityl-2′-O-{[(triisopropyl- silyl)oxy]methyl}-8-oxoguanosine-3′-yl-β-cyanoethyl-N,N-diisopropylphosphoramidite (5) was synt- hesized as a new phosphoramidite precursor unit for the synthesis of RNA. Compound 5 was successfully incorporated into the middle of the RNA sequences, and the synthesized RNAs were identified by MALDI-TOF mass measurements. Their properties were evaluated for formation of the RNA duplex and RNA/DNA heteroduplex. ORNs 1 and 4 containing 8-oxo-G can form base pairs with rC or dC in an anti conformation, while it can also interact with rA or dA in a syn conformation in the RNA duplex or RNA/DNA heteroduplex. The described synthetic method is therefore a useful procedure for the synthesis of ORN containing 8-oxo-G and contributes to the study of 8-oxo-G in RNA.     

[N,N′-Bis(salicylidene)-1,2-phenylenediamine]metal complexes with cell death promoting properties

We developed N,N′-bis(salicylidene)-1,2-phenylenediamine (salophene, 1) as a chelating agent for metal ions such as Mn(II/III), Fe(II/III), Co(II), Ni(II), Cu(II), and Zn(II). The resulting complexes, from which owing to the carrier ligand a selective mode of action is assumed, were tested for antiproliferative effects on the MCF-7 breast cancer cell line. The cytotoxicity in this assay depended on the nature of the transition metal used. Iron complexes in oxidation states +II and +III (3, 4) strongly reduced cell proliferation in a concentration-dependent manner, whereas, e.g., the manganese analogues 5 and 6 were only marginally active. Therefore, the [N,N′-bis(salicylidene)-1,2-phenylenediamine]iron(II/III) complexes 3 and 4 were selected for studies on the mode of action. Both complexes possessed high activity against various tumor cells, for instance, MDA-MB-231 mammary carcinoma cells as well as HT-29 colon carcinoma cells. They were able to generate reactive oxygen species, showed DNA binding, and induced apoptosis. Exchange of 1 by N,N′-bis(salicylidene)-1,2-cyclohexanediamine (saldach, 2) yielding complexes 7 and 8 reduced the in vitro effects drastically. An unequivocal mode of action cannot be deduced from these results, but it seems to be very likely that cell death is caused by interference with more than one intracellular target. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis of novel selenium containing sulfa drugs and their antibacterial activities

Synthesis of 3-[4-(N-substituted sulfamoyl)phenyl]-3,4-dihydro-4-oxo-7,9-dimethylpyri-do[3′,2′:4,5]selenolo[3,2-d]pyrimidines,7-[4-(N-substituted sulfamoyl)phenyl]-7,8-dihydro-8-oxo-3,4-diphenylpyrimido[4′,5′:4,5]selenolo [2,3-c]pyridazines and 1-[4-(N-substituted sulfamoyl)phenyl]-1,11-dihydro 11-oxo-4-methylpyrimido[4′,5′:4,5]selenolo[2,3-b]quinolines is reported. 4-Amino-N-pyrimidine-2-ylbenzene sulfonamide (a), 4-amino-N-(2,6-dimethylpyrimidin-4-yl)benzene sulfonamide (b), N-[(4-aminophenyl)sulfonyl] acetamide (c) with N-ethoxymethyleneamino of selenolo pyridine, selenolo pyridazine and selenolo quinoline derivatives respectively were obtained starting from 1-amino-N ⁴-substituted sulfanilamides. Spectroscopic data (IR, ¹H NMR, ¹³C NMR and Mass spectral) confirmed the structure of the newly synthesized compounds. Substituted pyrimidines, pyridazines and quinolines were screened for antibacterial activity against gram-positive and gram-negative bacteria. Selenolo derivative of N-[(4-aminophenyl)sulfonyl] acetamide (substitutent of sulfacetamide c) showed strong bactericidal effect against all the tested organisms. Selenolo[3,2-d]pyrimidin (substitutent a) showed a good bactericidal effect against Serratia marcescens, Staphylococcus aureus and Escherichia coli. Compounds selenolo[2,3-c]pyridazine (substitutent b), selenolo[2,3-b]quinoline(substitutents c)) exhibited a moderate bactericidal effect against Serratia marcescens. None of the synthesized seleno pyridazines has a considerable antimicrobial activity against the tested organisms. The minimum inhibitory concentration (MIC) of the most active compound-3-[4-(N-acetyl sulfamoyl)phenyl]-3,4-dihydro-4-oxo-7,9-dimethylpyrido[3′,2′:4,5]selenolo [3,2-d]pyrimidine was 10 mg ml⁻¹.     

Inhibitors of N α-acetyl-l-ornithine deacetylase: synthesis, characterization and analysis of their inhibitory potency

A series of N ^α-acyl (alkyl)- and N ^α-alkoxycarbonyl-derivatives of l- and d-ornithine were prepared, characterized, and analyzed for their potency toward the bacterial enzyme N ^α-acetyl-l-ornithine deacetylase (ArgE). ArgE catalyzes the conversion of N ^α-acetyl-l-ornithine to l-ornithine in the fifth step of the biosynthetic pathway for arginine, a necessary step for bacterial growth. Most of the compounds tested provided IC₅₀ values in the μM range toward ArgE, indicating that they are moderately strong inhibitors. N ^α-chloroacetyl-l-ornithine (1g) was the best inhibitor tested toward ArgE providing an IC₅₀ value of 85 μM while N ^α-trifluoroacetyl-l-ornithine (1f), N ^α-ethoxycarbonyl-l-ornithine (2b), and N ^α-acetyl-d-ornithine (1a) weakly inhibited ArgE activity providing IC₅₀ values between 200 and 410 μM. Weak inhibitory potency toward Bacillus subtilis-168 for N ^α-acetyl-d-ornithine (1a) and N ^α-fluoro- (1f), N ^α-chloro- (1g), N ^α-dichloro- (1h), and N ^α-trichloroacetyl-ornithine (1i) was also observed. These data correlate well with the IC₅₀ values determined for ArgE, suggesting that these compounds might be capable of getting across the cell membrane and that ArgE is likely the bacterial enzymatic target.     

An Efficient Method for the Synthesis of β-d-Ribonucleosides Catalyzed by Metal Iodides

Abstract

Several β-d-ribonucleosides were synthesized in high yields under mild conditions by N-glycosylations of methyl 2,3,5-tri-O-benzoyl-β-d-ribofuranosyl carbonate (1) with trimethylsilylated nucleoside bases in acetonitrile using a catalytic amount of metal iodide such as SnI₂, SbI₃ or TeI₄. A deprotection of N⁶ -benzoyl group of coupling product took place to a considerable extent when N⁶ -benzoyl-N⁶ , N⁹ -bis(trimethylsilyl)adenine was employed as a nucleoside base using SnI₂ or SnCI₂ as a catalyst while it was minimized when SbI₃ or TeI₄ was used. Further, the N-glycosylation of 1 with 7-trimethylsilyltheophylline in the presence of a catalytic amount of metal iodide was more effectively achieved in nitrile solvents other than acetonitrile.

     

SYNTHESIS OF N 6-ALKYLATED ADENOSINE DERIVATIVES

Abstract

N ⁶-ablated adenosine can be synthesized by reduction of the corresponding carboxylic acid amides using Lm. Starting from 2′,3′-O-isopropylidene adenosine, N ⁶-ethyladenosine, N ⁶-propyladenosine, N ⁶-isobutyladenosine, N ⁶-benzyladenosine and N ⁶-furfuryladenosine were obtained in a three step procedure (acylation, reduction, deprotection).     

Hybrid α/β-peptides: For-Met-Leu-Phe-OMe analogues containing geminally disubstituted β2,2- and β3,3-amino acids at the central position

Summary. The two fMLF-OMe analogues For-Met-β³hAc₆c-Phe-OMe (6) and For-Met-β²hAc₆c-Phe-OMe (12) and their corresponding N-Boc derivatives 5 and 11 have been synthesized and their biological activity towards human neutrophils evaluated. The N-formyl peptides 6 and 12 exhibit good activity as chemoattractans and 12 is highly active in superoxide anion production. The preferred solution conformation of the two N-formyl derivatives has been discussed.     

Peptide Analogues of DNA Consisting of l-α-Amino-γ-thymine Butyric Acid and l-Valine Subunits

Abstract

Reaction of N-Boc-L-homoserine benzylester with N³ -benzoylthymine under Mitsunobu conditions afforded N-Boc-L-α-amino-γ-N³ -benzoylthymine butyric acid benzylester. After removal of the N-benzoyl and O-benzyl protecting group, this compound was used in solution phase peptide synthesis.