Syntheses of 2″,3″-Dideoxy-L-Glycero-Pentofuranosyl C-Nucleosides

Abstract

2′,3′ -Dideoxy-L-C-nucleosides, 4-amino-8-(2,3-dideoxy-L-glyceropento-furanosyl)pyrazolo[1,5-a]-1,3,5-triazines (9 and 10), 4-amino-7-(2,3-dideoxy-L-glycero-pentofuranosyl)-3H,5H-pyrrolo[3,2-d]pyrimidines (17 and 18), 7-(2,3-dideoxy-L-glyceropentofuranosyl)-4-oxo-3H,5H-pyrrolo[3,2-d]pyrimidines (23 and 24) and 2,4-diamino-5-(2,3-dideoxy-L-glyceropentofuranosyl)pyrimidines (28 and 29) have been synthesized from L-gulonic γ-lactone 1.     

Novel Spironucleosides: 1″,3″-Thiazolidine-2″-Spiro-3′-3′-Deoxyuridine Derivatives

Abstract

Reaction of 2′,5′-di-O-TBDMS-3′-ketouridine 1 with L-cysteine yielded in good yield a resolvable mixture of the two expected epimeric spironucleosides 2 and 3. Amidification of their carboxylic group took place readily and the ribo carboxamide 4 was oxidized to the corresponding sulfoxide 6. Despite their similarity to TSAO derivatives these compounds did not exhibit usable anti-HIV activity.     

Synthesis of O-β-D-Ribofuranosyl-(1″-2′)-adenosine-5″-O-phosphate

Abstract

The first synthesis of O-β-D-ribofuranosyl-(1″-2′)-adenosine-5″-O-phosphate starting from protected 2′-O-β-D-ribofuranosyladenosine has been performed.     

2-[(4″-Hydroxy-3′-methoxy)-phenoxy]-4-(4″-hydroxy-3″-methoxy-phenyl)-8-hydroxy-6-oxo-3-oxabicylo[3.3.0]-7-octene: unusual product of the soybean lipoxygenase-catalyzed oxygenation of curcumin

Racemic (1SR,2SR,4SR,5SR)-2-[(4′-hydroxy-3′-methoxy)-phenoxy]-4-(4″-hydroxy-3″-methoxy-phenyl)-8-hydroxy-6-oxo-3-oxabicyclo[3.3.0]-7-octene (2, C₂₁H₂₀O₈) was isolated as major product of soybean lipoxygenase action on curcumin (1, C₂₁H₂₀O₆). The structure of 2 was elucidated by HPLC-APCI-MS and tandem MS, ¹H, ¹³C, DEPT, H,H-COSY, H,C-HMQC, H,C-HMBC and phase sensitive 2D NOESY NMR techniques. For kinetic studies the rate of substrate degradation was followed spectrophotometrically at 430 nm, and the rate of oxygen consumption was measured polarographically. As evaluated by both methods, K_m for 1 was about four times higher than that obtained for linoleic acid (as the best substrate for soybean lipoxygenase); V_max was reduced five-fold. Lipoxygenase-mediated oxygenation of 1 was confirmed by the following criteria: (i) curcumin did not react with inactivated lipoxygenase; (ii) the enzymatic reaction was strongly inhibited by inhibitors such as BHA, deferoxamine and HgCl₂; (iii) oxygen consumption (measured polarographically) and curcumin degradation (measured photometrically) were shown to occur simultaneously at a ratio of 0.8 to 1, suggesting insertion of oxygen into 1 by lipoxygenase; (iv) molecular mass estimation by APCI-MS showed a shift of 32 in molecular mass from 1 (M_r 368) to 2 (M_r 400) being equivalent to an insertion of dioxygen. Curcumin meets none of the common features for lipoxygenase substrates and, therefore, may represent a new type of substrates for this enzyme.     

Functionaleation of Nucleoside Analogs: Regiospecific Conversion of 4″-Hydroxyl Groups to Thioesters and Deoxygenation of 3′-Hydroxyl Groups

Abstract

Nucleoside analogs 3a-e were conveniently functionalized by regiospecifically converting 4″-hydroxyl groups to thioesters 4a-e (>90% yield) and reducing 3-hydroxyl groups to give building blocks 2a-e in 85–90% yields.     

Apigenin 7-glucoside and its 2″- and 6″-acetates from ligulate flowers of Matricaria chamomilla

Dried ligulate flowers of Matricaria chamomilla contain 7–9% glucosides of apigenin and 0.3–0.5% free apigenin. Glucosides were identified as apigenin 7-glucoside and a 1:3 mixture of the 2″- and 6″-acetates, as determined by ¹³C NMR analysis.     

Synthesis and Properties of Oligoribonucleotide Analogues Having Amide (3″-CH2-CO-NH-5′) Internucleoside Linkages

Abstract

Amide linked ribonucleoside dimer 5 was prepared and converted into selectively protected H-phosphonate building block 9. Oligoribonucleotide duplexes having amide linkages at selected sites were synthesized and their stability was studied by UV melting experiments.     

Frequency Dependence of Electrical Coupling in Deiters″ Cells of the Guinea Pig Cochlea

Immunolabeling with antibodies against connexins 26 and 30 showed that, in the guinea pig cochlea, supporting Deiters″ cells are massively interconnected and form an orderly network within the organ of Corti. In paired patch-clamp recordings the coupling ratio (CR) of adjacent Deiters″ cells at the apex of the cochlea (～0.31) was 3-fold smaller than in isolated cell pairs due to shunting afforded by multicellular connectivity. With sinusoidal current stimuli the delay in signal propagation between adjacent cells increased with increasing frequency whereas the amplitude did not change significantly up to 200 Hz (corner frequency F_c ～220 Hz). Depolarizing voltage commands applied to an outer hair cell (OHC) elicited outward potassium currents in the OHC and inward currents in the abutting Deiters″ cells, supplying direct evidence for potassium buffering in the organ of Corti. Computational analysis indicates that electrical signals injected into a Deiters″ cell are transmitted across a network segment spanning 8 cell diameters. Thus electrical coupling in the organ of Corti is unlikely to influence the selectivity of frequency filtering performed mechanically by the mammalian cochlea.     

Effect of substitution at N″-position of N'-hydroxy-N-amino guanidines on tumor cell growth

Structural modification of one of our earlier reported lead molecule (ABNM13) has been carried out to study the effect of different substituents at the N″-position of N-hydroxy-N'-amino guanidines (HAGs) on their anticancer activity. Compounds with electron donating substituents were found to be less active. In contrast, those with electron withdrawing groups were found favorable for anticancer activity. The obtained results provide significant SAR information that may be useful for further drug designing with HAGs.     

Synthesis of 4″-O-desosaminyl clarithromycin derivatives and their anti-bacterial activities

A series of new 4″-O-desosaminyl clarithromycin derivatives were designed and synthesized. The efficient synthesis routes of 6-deoxy-desosamine donors 8 and 11 were developed and the methodology of glycosylation of clarithromycin 4″-OH with desosamine was studied. The activities of the target compounds were tested against a series of macrolide-sensitive and macrolide-resistant pathogens. Some of them showed activities against macrolide sensitive pathogens, and compounds 19 and 22 displayed significant improvement of activities against sensitive pathogens and two strains of MRSE, which verified the importance of desosamine in the interaction of macrolide and its receptor, and offered valuable information of the SAR of macrolide 4″-OH derivatives.     

Studies Towards the Large Scale Chemical Synthesis of the Precursors of Ribonucleosides-3′,4′,5′,5″- 2H 4 and -2′,3′,4′,5′,5″- 2H 5

Abstract

A summary delineating the large scale synthetic studies to prepare labeled precursors of ribonucleosides-3′,4′,5′,5″- ²H ₄ and -2′,3′,4′,5′,5″- ²H ₅ from D-glucose is presented. The recycling of deuterium-labeled by-products has been devised to give a high overall yield of the intermediates and an expedient protocol has been elaborated for the conversion of 3-O-benzyl-α,β-D-allofuranose-3,4-d ₂ 6 to 1-O-methyl-3-O-benzyl-2-O-t-butyldimethylsilyl-α,β-D-ribofuranose-3,4,5,5′-d ₄ 16 (precursor of ribonucleosides-3′,4′,5′,5″- ²H ₄ ) or to 1-O-methyl-3,5-di-O-benzyl-α,β-D-ribofuranose-3,4,5,5′-d ₄ 18 (precursor of ribonucleosides-3′,4′,5′,5″- ²H ₄ ).     

Synthesis of [1-[2′,5′-bis-O-(t-Butyldimethylsilyl)-β- L-ribofuranosyl] thymine]-3′-spiro-5″-(4″-amino-1″,2″-oxathiole-2″,2″-dioxide) (L-TSAO-T)

Abstract

Derivatives of TSAO-T based upon pentofuranose sugars with the L-configuration have been prepared and evaluated as inhibitors of HIV-1 induced cytopathicity.     

Two isovitexin 2″-O-glycosides from primary leaves of Secale cereale

Two isovitexin 2″-O-glycosides have been isolated from primary leaves of rye and identified as isovitexin 2″-O-arabinoside and isovitexin 2     

Biotransformation of puerarin into puerarin-6″-O-phosphate by Bacillus cereus

The biotransformation of puerarin catalyzed by Bacillus cereus NT02 was studied. A primary screening was carried out using 307 strains of bacteria isolated from soil which were able to grow in the presence of puerarin. Strain NT02, identified as B. cereus, was able to convert puerarin into puerarin-6″-O-phosphate. Under the optimum conditions, resting cells of B. cereus NT02 converted 27% of added 0.4 g/l puerarin into puerarin-6″-O-phosphate that was characterized by MS, ¹³C NMR, ³¹P NMR. The activity of puerarin-6″-O-phosphate was 25 times higher than that of puerarin in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging system. The water solubility of puerarin-6″-O-phosphate was 85.4 times higher than that of puerarin.     

Synthesis and Properties of O-β-D-Ribofuranosyl-(1″-2′)-Adenosine-5″-O-Phosphate and Its Derivatives

Abstract

The synthesis of O-β-D-ribofuranosyl-(1″-2′)-adenosine-5″-O-phosphate and its suitably protected derivative for oligonucleotide synthesis have been developed.     

6′-substituted and 6′,6″-disubstituted derivatives of raffinose

The reaction of 6′-chloro-6′-deoxyraffinose deca-acetate with a variety of nucleophilic anions (Br^-,I^-,N^-₃) gave the corresponding 6′-substituted raffinoses. The 6′-azide was further converted into 6′-amino-6′-deoxyraffinose, isolated as its N-acetyl derivative, and silver fluoride-induced elimination of hydrogen iodide from the 6′-iodide gave the 6′-deoxy-5′-ene. Treatment of 6′-chloro-6′-deoxyraffinose and 6′,6″-dichloro-6′,6″-dideoxyraffinose with base afforded, respectively, 3′,6′-anhydro-and 3′,6′;3″,6″-dianhydro-raffinose in high yields. In addition, the dichloride was converted into 6′,6″-diazido-6′,6″-dideoxyraffinose.     

Identification of 4″-isovaleryl-spiramycin III produced by Bacillus sp. fmbJ

The production of secondary metabolites with antibiotic properties is a common characteristic to Bacillus spp. These metabolites not only have diverse chemical structures but also have a wide range of bioactivities with medicinal and agricultural interests such as antibiotic. Bacillus sp. fmbJ has been found to produce lipopeptides fengycin and surfactin in accordance with our previous report. In this study, another antimicrobial substance was separated and purified from the culture supernatant of strain fmbJ using the silica gel column chromatography and preparative reversed-phase high-performance liquid chromatography. By means of electrospray ionization mass spectroscopy, infrared spectroscopy, and nuclear magnetic resonance, the antagonistic compound was determined to be 4″-isovaleryl-spiramycin III with the molecular weight of 982 Da. This report is the first to introduce the finding of spiramycin produced from Bacillus sp. The study provides a novel source for the production of spiramycin in pharmaceutical industries.     

Aminoglycoside-3″-adenyltransferase confers resistance to spectinomycin and streptomycin in Nicotiana tabacum

The bacterial gene aad A encodes the enzyme aminoglycoside-3-adenyltransferase that confers resistance to spectinomycin and streptomycin in Escherichia coli. Chimeric genes have been constructed for expression in plants, and were introduced into Nicotiana tabacum by Agrobacterium binary transformation vectors. Spectinomycin or streptomycin in selective concentrations prevent greening of N. tabacum calli. Transgenic clones, however, formed green calli on selective media containing spectinomycin, streptomycin, or both drugs. Resistance was inherited as a dominant Mendelian trait in the seed progeny. Resistance conferred by the chimeric aad A gene can be used as a color marker similar to the resistance conferred by the streptomycin phosphotransferase gene to streptomycin.     

The efficacy and acceptability of the ″prostaglandin impact″ in inducing complete abortion during the second week after the missed menstrual period

Twenty-two pregnant patients were exposed, 12±1 days after their missed menstrual period, to a single intrauterine dose of 5mg PG F2_α, to provoke a PG ″Impact″ (PGI) and through it legal abortion. The PGI, delivered through the cervix during 10 minutes, induced 83±9mm Hg contracture in 20±3 minutes. Cyclic IUP reached 102±10mm Hg only in 116±14 minutes, it was then sustained for about 2 hours and subsequently declined.During the evolution of IUP uterine bleeding appeared, progesterone (P) and estradiol 17_β (E₂) started to decrease and continued decreasing. At 24 hours after PGI, P-withdrawal was 44% (P<0.05), bleeding continued and cervical dilatation approximated 1cm. Subsequently uterine bleeding (containing tissue fragments) continued and out of 22 women 20 aborted completely. After 3–5 days bleeding declined, the pregnancy tests became negative and normal menstrual periods one month after PGI provided the desired end points of the study. Complete abortions, simulating the symptoms of delayed menstrual periods, had a high Abortion Score of 95 and in the sedated patients the side effects were infrequent, mild and acceptable. This clinical outcome encourages extensive field trials.None of the patients aborted during the short lived period of exogenous PG stimulation. However, the continued steroid withdrawals indicated that PGI damaged the endocrine function of the ovum and the luteotrophic support of the corpus luteum. Therefore, if it was PG which completed abortion eventually, it had to be the endogenous compound, having become effective in physiological concentrations, due to the threshold-lowering action of P-withdrawal.