Synthesis of 3′,5′‐Cyclic Phosphate and Thiophosphate Esters of 2′‐C‐Methyl Ribonucleosides

2′‐C‐Methylnucleosides are known to exhibit antiviral activity against Hepatitis C virus. Since the inhibitory activity depends on their intracellular conversion to 5′‐triphosphates, dosing as appropriately protected 5′‐phosphates or 5′‐phosphorothioates appears attractive. For this purpose, four potential pro‐drugs of 2′‐C‐methylguanosine, i.e., 3′,5′‐cyclic phosphorothioate of 2′‐C‐methylguanosine and 2′‐C,O⁶‐dimethylguanosine, 1 and 2 , respectively, the S‐[(pivaloyloxy)methyl] ester of 2′‐C,O⁶‐dimethylguanosine 3′,5′‐cyclic phosphorothioate and the O‐methyl ester of 2′‐C,O⁶‐dimethylguanosine 3′,5′‐cyclic phosphate, 3 and 4 , respectively, have been prepared.     

Oligonucleotides Containing Novel 4′‐C‐ or 3′‐C‐(Aminoalkyl)‐Branched Thymidines

The synthesis of four novel 3′‐C‐branched and 4′‐C‐branched nucleosides and their transformation into the corresponding 3′‐O‐phosphoramidite building blocks for automated oligonucleotide synthesis is reported. The 4′‐C‐branched key intermediate 11 was synthesized by a convergent strategy and converted to its 2′‐O‐methyl and 2′‐deoxy‐2′‐fluoro derivatives, leading to the preparation of novel oligonucleotide analogues containing 4′‐C‐(aminomethyl)‐2′‐O‐methyl monomer X and 4′‐C‐(aminomethyl)‐2′‐deoxy‐2′‐fluoro monomer Y (Schemes 2 and 3). In general, increased binding affinity towards complementary single‐stranded DNA and RNA was obtained with these analogues compared to the unmodified references (Table 1). The presence of monomer X or monomer Y in a 2′‐O‐methyl‐RNA oligonucleotide had a negative effect on the binding affinity of the 2′‐O‐methyl‐RNA oligonucleotide towards DNA and RNA. Starting from the 3′‐C‐allyl derivative 28 , 3′‐C‐(3‐aminopropyl)‐protected nucleosides and 3′‐O‐phosphoramidite derivatives were synthesized, leading to novel oligonucleotide analogues containing 3′‐C‐(3‐aminopropyl)thymidine monomer Z or the corresponding 3′‐C‐(3‐aminopropyl)‐2′‐O,5‐dimethyluridine monomer W (Schemes 4 and 5). Incorporation of the 2′‐deoxy monomer Z induced no significant changes in the binding affinity towards DNA but decreased binding affinity towards RNA, while the 2′‐O‐methyl monomer Z induced decreased binding affinity towards DNA as well as RNA complements (Table 2).     

Stilbenoids and Phenols in Acanthopanax brachypus

Three new stilbenoids, including α‐(3′‐O‐β‐D ‐glucopyranosyl‐5′‐methoxyphenyl)‐2‐methoxy‐3‐methylbenzofuran ( 1 ), 4‐methyl‐(E)‐resveratrol 3‐(2″‐p‐hydroxybenzoyl)‐O‐β‐D ‐glucopyranoside ( 2 ), and 5‐O‐methyl‐(E)‐resveratrol 3‐(6″‐acetyl)‐O‐β‐D ‐glucopyranoside ( 3 ), together with six known stilbenoids and phenols, acetovanillone 1‐(6′‐vanilloyl)‐O‐β‐D ‐glucopyranoside, eugenyl‐O‐β‐D ‐glucopyranoside, α‐(3′‐hydroxy‐5′‐methoxy‐2′‐methylphenyl)‐2‐hydroxybenzofuran, α‐(3′‐hydroxy‐5′‐methoxyphenyl)‐2‐hydroxybenzofuran, pinosilvin 3‐O‐β‐D ‐glucopyranoside, and (E)‐resveratrol 3‐(6″‐galloyl)‐O‐β‐D ‐glucopyranoside were isolated from the EtOH extract of the stem bark of Acanthopanax brachypus. Their structures were determined by spectral analysis including extensive 2D‐NMR spectral analyses. Compounds 2 and 3 exhibited weak cytotoxicity against human tumor A549 cell line (IC₅₀ values of 4.87 and 5.63 μM , resp.).     

Four New Lariciresinol‐Based Lignan Glycosides from the Roots of Rhus javanica var. roxburghiana

The four new lariciresinol‐based lignan glycosides, (?)‐lariciresinol 4′‐(6″‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 1 ), (?)‐lariciresinol 4′‐(4″,6″‐di‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 2 ), 5,5′‐dimethoxylariciresinol 4′‐(4″,6″‐di‐O‐feruloyl)‐β‐D ‐glucopyranoside) ( 3 ), and 4‐O‐[α‐(1,2‐dihydroxyethyl)syringyl]‐5,5′‐dimethoxylariciresinol 4′‐(4″,6″‐di‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 4 ), together with two known ones, lariciresinol 4′‐β‐D ‐glucopyranoside) ( 5 ) and tortoside B ( 6 ), were isolated from the BuOH extract of Rhus javanica var. roxburghiana roots, and their structures were established by means of various spectroscopic techniques.     

Oligonucleotides Containing Disaccharide Nucleosides

Disaccharide nucleosides with 2′‐O‐(D ‐arabinofuranosyl), 2′‐O‐(L ‐arabinofuranosyl), 2′‐O‐(D ‐ribopyranosyl), 2′‐O‐(D ‐erythrofuranosyl), and 2′‐O‐(5‐azido‐5‐deoxy‐D ‐ribofuranosyl) substituents were synthesized. These modified nucleosides were incorporated into oligonucleotides (see Table). Single substitution resulted in a ΔT_m of +0.5 to −1.4° for DNA/RNA and a ΔT_m of −0.8 to −4.7° for DNA/DNA duplexes. These disaccharide nucleosides can be well accommodated in RNA/DNA duplexes, and the presence of a NH₂−C(5″) group has a beneficial effect on duplex stability.     

Synthesis and Characterization of New 5‐Linked Pinoresinol Lignin Models

Pinoresinol structures, featuring a β‐β′‐linkage between lignin monomer units, are important in softwood lignins and in dicots and monocots, particularly those that are downregulated in syringyl‐specific genes. Although readily detected by NMR spectroscopy, pinoresinol structures largely escaped detection by β‐ether‐cleaving degradation analyses presumably due to the presence of the linkages at the 5 positions, in 5‐5′‐ or 5‐O‐4′‐structures. In this study, which is aimed at helping better understand 5‐linked pinoresinol structures by providing the required data for NMR characterization, new lignin model compounds were synthesized through biomimetic peroxidase‐mediated oxidative coupling reactions between pre‐formed (free‐phenolic) coniferyl alcohol 5‐5′‐ or 5‐O‐4′‐linked dimers and a coniferyl alcohol monomer. It was found that such dimers containing free‐phenolic coniferyl alcohol moieties can cross‐couple with the coniferyl alcohol producing pinoresinol‐containing trimers (and higher oligomers) in addition to other homo‐ and cross‐coupled products. Eight new lignin model compounds were obtained and characterized by NMR spectroscopy, and one tentatively identified cross‐coupled β‐O‐4′‐product was formed from a coniferyl alcohol 5‐O‐4′‐linked dimer. It was demonstrated that the 5‐5′‐ and 5‐O‐4′‐linked pinoresinol structures could be readily differentiated by using heteronuclear multiple‐bond correlation (HMBC) NMR spectroscopy. With appropriate modification (etherification or acetylation) to the newly obtained model compounds, it would be possible to identify the 5‐5′‐ or 5‐O‐4′‐linked pinoresinol structures in softwood lignins by 2D HMBC NMR spectroscopic methods. Identification of the cross‐coupled dibenzodioxocin from a coniferyl alcohol 5‐5′‐linked moiety suggested that thioacidolysis or derivatization followed by reductive cleavage (DFRC) could be used to detect and identify whether the coniferyl alcohol itself undergoes 5‐5′‐cross‐linking during lignification.     

New approach to l'C‐modified riboside scaffold via stereoselective functionalization of D‐(+)‐ribonic‐y‐lactone

We describe the preparation and spectroscopic properties of a novel class of nucleoside analogues in which a phenyl sulfonyl methylene group is attached to the 1′‐carbon atom of P‐D‐ribofuranose. The glyco‐sylation of 5‐O‐(tert‐butyldiphenylsilyl)‐2,3‐O‐isopropylidene‐D‐ribofuranolactone lb with phenyl methyl‐lithium sulfone in THF at ?60° C afforded 5‐O‐(tert‐butyldiphenylsilyl)‐1′‐(benzenesulfonylmethylene)‐2′,3′‐O‐isopropylidene‐α‐D‐ribofuranose 2b . When subjected to deoxydative reaction conditions with boron trifluoride etherate in the presence of triethylsilane at ?45° C, lactol 2b was converted into 2′,3′‐O‐isopro‐pylidene‐1′‐deoxy‐1′‐(benzenesulfonylmethylene)‐β‐D‐ribofuranose 4b with excellent stereocontrol over the anomeric carbon in moderate yield. This method has the potential for the development of a wider array of useful probes derived from 1′‐deoxy‐β‐D‐ribofuranose for nucleic acid research and for antisense therapeutic agents through further functionalization of the coupled sulfonyl group.     

Synthetic Study of Carthamin: Biomimetic Synthesis of Carthamin Model via Peroxidase‐Catalyzed Oxidative Decarboxylation of Its Precursor Model

A chiral carthamin model (3S,3′S)‐1‐[5‐acetyl‐2,6‐diketo‐3‐C‐β‐d ‐glucopyranosylcyclohex‐4‐enylidene]‐1′‐[5′‐acetyl‐3′‐C‐β‐d ‐glucopyranosyl‐2′,3′,4′‐trihydroxy‐6′‐oxocyclohexa‐1′,4′‐dienyl]methane, in which two cinnamoyl groups were replaced by an acetyl group, was synthesized by the dimerization of (S)‐2‐acetyl‐4‐C‐(per‐O‐acetyl‐β‐d ‐glucopyranosyl)cyclohexadienone with glyoxylic acid, followed by peroxidase‐catalyzed oxidative decarboxylation and de‐O‐acetylation, or de‐O‐acetylation and peroxidase‐catalyzed oxidative decarboxylation. The corresponding total yields were 12.5% or 17.1% from 3‐C‐(per‐O‐acetyl‐β‐d ‐glucopyranosyl)phloroacetophenone, and the reaction pathway was identical to the biosynthetic pathway.     

Five Aromatics Bearing a 4‐O‐Methylglucose Unit from Cordyceps cicadae

Five new aromatics bearing a 4‐O‐methylglucose unit, namely 3‐methoxy‐1,4‐hydroquinone 1‐(4′‐O‐methyl‐β‐glucopyranoside) (=4‐hydroxy‐3‐methoxyphenyl 4‐O‐methyl‐β‐glucopyranoside; 1 ), 3‐methoxy‐1,4‐hydroquinone 4‐(4′‐O‐methyl‐β‐glucopyranoside) (=4‐hydroxy‐2‐methoxyphenyl 4‐O‐methyl‐β‐glucopyranoside; 2 ), vanillic acid 4‐(4′‐O‐methyl‐β‐glucopyranoside) (=3‐methoxy‐4‐[(O‐methyl‐β‐glucopyranosyl)oxy]benzoic acid; 3 ), 5‐methoxycinnamic acid 3‐O‐(4′‐O‐methyl‐β‐glucopyranoside) (=(2E)‐3‐{3‐methoxy‐5‐[(4‐O‐methyl‐β‐glucopyranosyl)oxy]phenyl}prop‐2‐enoic acid; 4 ), and naphthalene‐1,8‐diol 1,8‐bis(4′‐O‐methyl‐β‐glucopyranoside) (=naphthalene‐1,8‐diyl bis(4‐O‐methyl‐β‐glucopyranoside; 5 ), were isolated from the cultivated Cordyceps cicadae mycelia, together with thirteen known compounds. Their structures were determined by spectroscopic methods. The absolute configurations of the sugar units were not determined.     

An Efficient Synthesis of 3′‐Amino‐3′‐deoxyguanosine from Guanosine

3′‐Amino‐3′‐deoxyguanosine was synthesized from guanosine in eight steps and 58% overall yield. The 2′,3′‐diol of 5′‐O‐[(tert‐butyl)diphenylsilyl]‐2‐N‐[(dimethylamino)methylidene]guanosine was reacted with α‐acetoxyisobutyryl bromide and treated with 0.5n NH₃ in MeOH to yield 9‐{2′‐O‐acetyl‐3′‐bromo‐5′‐O‐[(tert‐butyl)diphenylsilyl]‐3′‐deoxy‐β‐D ‐xylofuranosyl]‐2‐N‐[(dimethylamino)methylidene]guanine, which was reacted with benzyl isocyanate, NaH, and then 3.0n NaOH, and finally with Pd/C (10%) and HCO₂NH₄ in EtOH/AcOH to afford 3′‐amino‐3′‐deoxyguanosine.     

Spontaneous Aminoacylation of a RNA Sequence Containing a 3′‐Terminal 2′‐Thioadenosine

We report the synthesis of a modified 8mer RNA sequence, (C‐C‐C‐C‐A‐C‐C‐(2′‐thio)A)‐RNA 5′‐(dihydrogen phosphate) ( 9 ) containing a 3′‐terminal 2′‐thioadenosine (Schemes 2 and 3), and its spontaneous and site‐specific aminoacylation with the weakly activated amino acid thioester H Phe SPh ( 12 ). This reaction, designed in analogy to the ‘native chemical ligation’ of oligopeptides, occurs efficiently in buffered aqueous solutions and under a wide range of conditions (Table). At pH values between 5.0 and 7.4, two products, the 3′‐O‐monoacylated and the 3′‐O,2′‐S‐diacylated RNA sequences 10 and 11 are formed fast and quantitatively (Scheme 4). At pH 7.4 and 37°, the 3′‐O‐monoacylated product 10 is formed as major product in situ by selective hydrolysis of the O,S‐diacylated precursor 11 . Additionally, the preparation and isolation of the relevant 3′‐O‐monoacylated product 10 was optimized at pH 5. The here presented concept could be employed for a straightforward aminoacylation of analogously modified tRNAs.     

Synthesis of 2′‐O‐[(Triisopropylsilyl)oxy]methyl (= tom)‐Protected Ribonucleoside Phosphoramidites Containing Various Nucleobase Analogues

The first results of a study aiming at an efficient preparation of a large variety of 2′‐O‐[(triisopropylsilyl)oxy]methyl(= tom)‐protected ribonucleoside phosphoramidite building blocks containing modified nucleobases are reported. All of the here presented nucleosides have already been incorporated into RNA sequences by several other groups, employing 2′‐O‐tbdms‐ or 2′‐O‐tom‐protected phosphoramidite building blocks (tbdms = (tert‐butyl)dimethylsilyl). We now optimized existing reactions, developed some new and shorter synthetic strategies, and sometimes introduced other nucleobase‐protecting groups. The 2′‐O‐tom, 5′‐O‐(dimethoxytrityl)‐protected ribonucleosides N²‐acetylisocytidine 5 , O²‐(diphenylcarbamoyl)‐N⁶‐isobutyrylisoguanosine 8 , N⁶‐isobutyryl‐N²‐(methoxyacetyl)purine‐2,6‐diamine ribonucleoside (= N⁸‐isobutyryl‐2‐[(methoxyacetyl)amino]adenosine) 11 , 5‐methyluridine 13 , and 5,6‐dihydrouridine 15 were prepared by first introducing the nucleobase protecting groups and the dimethoxytrityl group, respectively, followed by the 2′‐O‐tom group (Scheme 1). The other presented 2′‐O‐tom, 5′‐O‐(dimethoxytrityl)‐protected ribonucleosides inosine 17 , 1‐methylinosine 18 , N⁶‐isopent‐2‐enyladenosine 21 , N⁶‐methyladenosine 22 , N⁶,N⁶‐dimethyladenosine 23 , 1‐methylguanosine 25 , N²‐methylguanosine 27 , N²,N²‐dimethylguanosine 29 , N⁶‐(chloroacetyl)‐1‐methyladenosine 32 , N⁶‐{{{(1S,2R)‐2‐{[(tert‐butyl)dimethylsilyl]oxy}‐1‐{[2‐(4‐nitrophenyl)ethoxy]carbonyl}propyl}amino}carbonyl}}adenosine 34 (derived from L ‐threonine) and N⁴‐acetyl‐5‐methylcytidine 36 were prepared by nucleobase transformation reactions from standard, already 2′‐O‐tom‐protected ribonucleosides (Schemes 2–4). Finally, all these nucleosides were transformed into the corresponding phosphoramidites 37 – 52 (Scheme 5), which are fully compatible with the assembly and deprotection conditions for standard RNA synthesis based on 2′‐O‐tom‐protected monomeric building blocks.     

Individual Isomers of Dinucleoside Boranophosphates as Synthons for Incorporation into Oligonucleotides: Synthesis and Configurational Assignment

Individual isomers of the protected boranophosphates 5a and 5b , i.e., the N⁶‐benzyl‐2′‐deoxy‐5′‐O‐(4,4′‐dimethoxytrityl)adenosin‐3′‐yl 2′‐deoxy‐4‐O‐(4‐nitrophenyl)uridin‐5′‐yl boranophosphates, were synthesized via stereospecific silylation and boronation of their H‐phosphonate precursors. 2D‐NMR Spectroscopic studies yielded an initial assignment of the isomer configuration, which was further confirmed unambiguously by a parallel chemical synthesis. Deprotection of the `dimers' 5a and 5b yielded the individual [P(R)]‐ and [P(S)]‐isomers 7a and 7b , respectively, i.e., the 2′‐deoxyadenosin‐3′‐yl 2′‐deoxycytidin‐5′‐yl boranophosphates. Their substrate properties toward phosphodiesterase I were identical to those of the previously characterized isomers of dithymidine boranophosphate. The protected `dimers' 5a and 5b can be used as synthons to incorporate the boranophosphate linkage with a defined configuration to selected positions of an oligonucleotide chain.     

Reliable Chemical Synthesis of Oligoribonucleotides (RNA) with 2′‐O‐[(Triisopropylsilyl)oxy]methyl(2′‐O‐tom)‐Protected Phosphoramidites

A method for the introduction of the 2′‐O‐[(triisopropylsilyl)oxy]methyl (=tom) group into N‐acetylated, 5′‐O‐dimethoxytritylated ribonucleosides is presented. The corresponding 2′‐O‐tom‐protected phosphoramidite building blocks were obtained in pure form and were successfully employed for the routine synthesis of oligoribonucleotides on DNA synthesizers. Under DNA coupling conditions (2.5 min coupling time for a 1.5‐μmol synthesis scale) and with 5‐(benzylthio)‐1H‐tetrazole (BTT) as activator, 2′‐O‐tom‐protected phosphoramidites exhibited average coupling yields >99.4%. The combination of N‐acetyl and 2′‐O‐tom protecting groups allowed a reliable and complete two‐step deprotection, first with MeNH₂ in EtOH/H₂O and then with Bu₄NF in THF, without concomitant destruction of the product RNA sequences.     

The different modes of chiral [1,2,3]triazolo[5,1‐b][1,3,4]thiadiazines: crystal packing,conformation investigation and cellular activity

The crystal structures of four new chiral [1,2,3]triazolo[5,1‐b][1,3,4]thiadiazines are described, namely, ethyl 5′‐benzoyl‐5′H,7′H‐spiro[cyclohexane‐1,6′‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine]‐3′‐carboxylate, C₁₉H₂₂N₄O₃S, ethyl 5′‐(4‐methoxybenzoyl)‐5′H,7′H‐spiro[cyclohexane‐1,6′‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine]‐3′‐carboxylate, C₂₀H₂₄N₄O₄S, ethyl 6,6‐dimethyl‐5‐(4‐methylbenzoyl)‐6,7‐dihydro‐5H‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine‐3‐carboxylate, C₁₇H₂₀N₄O₃S, and ethyl 5‐benzoyl‐6‐(4‐methoxyphenyl)‐6,7‐dihydro‐5H‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine‐3‐carboxylate, C₂₁H₂₀N₄O₄S. The crystallographic data and cell activities of these four compounds and of the structures of three previously reported similar compounds, namely, ethyl 5′‐(4‐methylbenzoyl)‐5′H,7′H‐spiro[cyclopentane‐1,6′‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine]‐3′‐carboxylate, C₁₉H₂₂N₄O₃S, ethyl 5′‐(4‐methoxybenzoyl)‐5′H,7′H‐spiro[cyclopentane‐1,6′‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine]‐3′‐carboxylate, C₁₉H₂₂N₄O₄S, and ethyl 6‐methyl‐5‐(4‐methylbenzoyl)‐6‐phenyl‐6,7‐dihydro‐5H‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine‐3‐carboxylate, C₂₂H₂₂N₄O₃S, are contrasted and compared. For both crystallization and an MTT assay, racemic mixtures of the corresponding [1,2,3]triazolo[5,1‐b][1,3,4]thiadiazines were used. The main manner of molecular packing in these compounds is the organization of either enantiomeric pairs or dimers. In both cases, the formation of two three‐centre hydrogen bonds can be detected resulting from intramolecular N—H…O and intermolecular N—H…O or N—H…N interactions. Molecules of different enantiomeric forms can also form chains through N—H…O hydrogen bonds or form layers between which only weak hydrophobic contacts exist. Unlike other [1,2,3]triazolo[5,1‐b][1,3,4]thiadiazines, ethyl 5′‐benzoyl‐5′H,7′H‐spiro[cyclohexane‐1,6′‐[1,2,3]triazolo[5,1‐b][1,3,4]thiadiazine]‐3′‐carboxylate contains molecules of only the (R)‐enantiomer; moreover, the N—H group does not participate in any significant intermolecular interactions. Molecular mechanics methods (force field OPLS3e) and the DFT B3LYP/6‐31G+(d,p) method show that the compound forming enantiomeric pairs via weak N—H…N hydrogen bonds is subject to greater distortion of the geometry under the influence of the intermolecular interactions in the crystal. For intramolecular N—H…O and S…O interactions, an analysis of the noncovalent interactions (NCIs) was carried out. The cellular activities of the compounds were tested by evaluating their antiproliferative effect against two normal human cell lines and two cancer cell lines in terms of half‐maximum inhibitory concentration (IC₅₀). Some derivatives have been found to be very effective in inhibiting the growth of Hela cells at nanomolar and submicromolar concentrations with minimal cytotoxicity in relation to normal cells.     

Synthesis of a Thymidine Dimer Containing a Tetrazole‐2,5‐diyl Internucleosidic Linkage and Its Insertion into Oligodeoxynucleotides

Thymidine dimers in which the natural phosphodiester linkage has been replaced by a 2,5‐disubstituted tetrazole ring are synthesized and incorporated into oligodeoxynucleotides (ODNs). The synthesis is accomplished by two strategies based on an alkylation of 5′‐O‐trityl‐on and 5′‐O‐trityl‐off 3′‐deoxy‐3′‐(1H‐tetrazol‐5‐yl)thymidines with 5′‐iodo‐5′‐deoxythymidine in the presence of Et₃N, and the formation of only 2‐substituted tetrazol‐5‐yl linkages is observed in 89 and 46% yields, respectively. The nucleoside dimer formed is reacted with 4,4′‐dimethoxytrityl chloride (DMTCl), followed by treatment with 2‐cyanoethyl tetraisopropylphosphordiamidite in the presence of N,N‐diisopropylammonium tetrazolide, to afford the 5′‐O‐DMT‐protected dinucleoside phosphoramidite that is used for incorporation into ODNs on an automated DNA synthesizer. The modified ODNs with one and up to five tetrazole internucleosidic linkages are obtained in good yields. The thermal stability of DNA/DNA and DNA/RNA duplexes is studied by UV experiments and reported also.     

Seven New Phenolic Glucosides from Viburnum cylindricum

Seven new phenolic glucosides, 2′‐O‐acetylhenryoside ( 1 ), 2′,3′‐di‐O‐acetylhenryoside ( 2 ), 2′,6′‐di‐O‐acetylhenryoside ( 3 ), 2′,3′,6′‐tri‐O‐acetylhenryoside ( 4 ), 2′,3′,4′,6′‐tetra‐O‐acetylhenryoside ( 5 ), 2‐[(2,3‐di‐O‐acetyl‐β‐D ‐glucopyranosyl)oxy]‐6‐hydroxybenzoic acid ( 6 ), and 6‐hydroxy‐2‐[(2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐glucopyranosyl)oxy]benzoic acid ( 7 ), were isolated from the leaves and stems of Viburnum cylindricum, along with 26 known compounds (henryoside=2‐(β‐D ‐glucopyranosyloxy)‐6‐hydroxybenzoic acid [2‐(β‐D ‐glucopyranosyloxy)phenyl]methyl ester). The structures of the new compounds were established on the basis of chemical and spectroscopic evidences.     

Synthesis of 3′‐Thioamido‐Modified 3′‐Deoxythymidine 5′‐Triphosphates by Regioselective Thionation and Their Use as Chain Terminators in DNA Sequencing

The thioamide derivatives 3′‐deoxy‐5′‐O‐(4,4′‐dimethoxytrityl)‐3′‐[(2‐methyl‐1‐thioxopropyl)amino]thymidine ( 4a ) and 3′‐deoxy‐5′‐O‐(4,4′‐dimethoxytrityl)‐3′‐{{6‐{[(9H‐(fluoren‐9‐ylmethoxy)carbonyl]amino}‐1‐thioxohexyl}amino}thymidine ( 4b ) were synthesized by regioselective thionation of the corresponding amides 3a and 3b with 2,4‐bis(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane 2,4‐disulfide (Lawesson's reagent). The addition of exact amounts of pyridine to the reaction mixture proved to be essential for an efficient transformation. The thioamides were converted into the corresponding 5′‐triphosphates 6a and 6b . Compound 6a was chosen for DNA sequencing experiments, and 6b was further labelled with fluorescein (→ 8 ).     

Chemical Components of Seriphidium Santolium Poljak

A new biflavonoid glucoside, apigenin‐7‐O‐β‐D‐glucopyranoside‐(3′‐O‐7″)‐quercetin‐3″‐methyl ether ( 1 ) together with twenty known compounds, apigenin ( 2 ), luteolin ( 3 ), chrysoeriol ( 4 ), tricin ( 5 ), hispidulin ( 6 ), pectolinarigenin ( 7 ), eupatilin ( 8 ), 5,7‐dihydroxy‐6,3′,4′,5′‐tetramethoxyflavone ( 9 ), 5,7,4′‐trihydroxy‐6,3′,5′‐trimethoxyflavone ( 10 ), 3,6‐O‐dimethylquercetagetin‐7‐O‐β‐D‐glucoside ( 11 ), 6‐hydroxy‐5,7‐dimethoxy‐coumarin ( 12 ), taraxerol ( 13 ), taraxeryl acetate ( 14 ), a mixture of β‐sitosterol ( 15 ) and stigmasterol ( 16 ), a mixture of the n‐alkyl trans‐p‐coumarates ( 17 ), a mixture of the n‐alkyl trans‐ferulates ( 18 ), 2‐hydroxy‐4,6‐dimethoxyacetophenone ( 19 ), 4‐hydroxy‐2,6‐dimethoxyphenol‐1‐O‐β‐D‐glucopyranoside ( 20 ), and 2‐hydroxycinnamoyl‐β‐D‐glucopyranoside ( 21 ), were isolated from the whole plant of Seriphidium santolium Poljak. The structures of these compounds were determined by means of spectral and chemical studies.     

Flavone Glycosides from Strobilanthes Formosanus

Two new flavone glycosides, 3′‐hydroxy‐5,7‐dimethoxyflavone 4′‐O‐β‐D‐apiofuranoside ( 1 ), and 5,7‐dimethoxyflavone 4′‐O‐[β‐D‐apiofuranosyl(1→5)‐ β‐D‐glucopyranoside] ( 2 ) along with four known compounds, 4′‐hydroxy‐5,7‐dimethoxyflavone ( 3 ), 2,6‐dimethoxy‐1,4‐benzoquinone ( 4 ), lupeol ( 5 ) and betulin ( 6 ) were isolated from the stem and roots of Strobilanthes formosanus. Their structures were elucidated on the basis of their spectroscopic evidence.