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Electrochemical corrosion behavior of ternary tin-zinc-yttrium (Sn-9Zn-xY) solder alloys were investigated in aerated 3.5 wt.% NaCl solution using potentiodynamic polarization techniques, and the microstructure evolution was obtained by scanning electron microscope (SEM). Eight different compositions of Sn-9Zn-xY (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, and 0.30 wt.%) were compared by melting. The experimental results show that when the content of Y reached 0.06 wt.%, the grain size of Zn-rich phase became the smallest and the effect of grain refinement was the best, but there was no significant effect on the melting point. With the increases of Y content, the spreading ratio first increased and then decreased. When the content of Y was 0.06 wt.%, the Sn-9Zn-0.06Y solder alloy had the best wettability on the Cu substrate, which was increased by approximately 20% compared with Sn-9Zn. Besides, the electrochemical corrosion experimental shows that the Y can improve the corrosion resistance of Sn-9Zn system in 3.5 wt.% NaCl solution, and the corrosion resistance of the alloy is better when the amount of Y added is larger within 0.02–0.30 wt.%. Overall considering all performances, the optimal performance can be obtained when the addition amount of Y is 0.06.

Background Metal exposures are suspected to associate with the risk of hyperuricemia (HUA), but the current results are still conflicting. Objective To investigate the associations between multiple plasma metal exposures and HUA risk. Methods A cross-sectional study was conducted in 1406 Chinese Han adults who underwent routine physical examination in the Eighth Affiliated Hospital of Sun Yat-Sen University in Shenzhen. The plasma levels of 13 metals were measured by the inductively coupled plasma mass spectrometry (ICP-MS). Multivariable logistic, linear regression models, least absolute shrinkage and selection operator (LASSO) penalized regression analysis, and restricted cubic spline (RCS) models were applied to assess the associations. Results The median plasma uric acid concentration in HUA group (434 μmol/L) was significantly higher than that in non-HUA group (305 μmol/L). The multivariate-adjusted odds ratios (95% confidence intervals) of HUA were 1.62(1.08–2.43) for magnesium, 1.61(1.05–2.47) for copper, 1.62(1.06–2.49) for zinc, 1.87(1.26–2.81) for arsenic, 1.50(1.01–2.23) for selenium, and 1.70(1.16–2.49) for thallium based on the single-metal logistic regression models, comparing the highest versus the lowest quartile of metal levels. Further multi-metal logistic, linear regression models and the LASSO analysis all indicated positive associations of zinc, arsenic with HUA risk or uric acid levels. RCS model indicated an inverted V-shaped positive association between zinc levels and HUA risk (p for non-linearity = 0.048, p for overall association = 0.022), while arsenic levels showed a positive and linear dose-response relationship with HUA risk (p for non-linearity = 0.892, p for overall association Conclusions Higher plasma levels of zinc and arsenic might increase HUA risk and showed positive dose-response relationships. Further cohort studies in larger population are required to testify our findings.

The pollution from nuclear leaks and nuclear disasters (e.g. radioactive iodine) would cause serious harm to human beings and ecosystems for many years. Cocoon silk and deep eutectic solvents (DESs) are both green substances. DESs are easily synthesized, cheap, highly biocompatible and highly biodegradable. Here, we combine the removal of organic dyes and the capture of radioactive iodine by using green DES-pretreated cocoon silk. It is the first time organic dyes have been removed from wastewater by DES-disrupted silk for the purpose of favourably removing iodine. Organic dyes-captured DES-pretreated cocoon silk could be used to capture iodine efficiently. It opens a new route to dispose of one waste from nuclear energy with organic dyes from wastewater captured by green solvents-pretreated natural silk.

Background Heavy metal exposure induces oxidative stress, which is critical for adverse male reproductive health. Objective To explore the mediating effect of oxidative stress on the relationship of heavy metal exposure with semen quality. Methods Urinary levels of three oxidative stress markers, semen quality, and urinary arsenic, cadmium and lead were examined among 1020 men. Multivariate linear regression was applied to explore cross-sectional associations, and the role of oxidative stress as mediators was investigated. Results Quartiles of metals showed significant dose-dependent relationships with increasing levels of 8-hydroxy-2deoxyguanosine (8-OHdG), 8-iso-prostaglandin F2α (8-isoPGF2α) and 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA). Significant or suggestive associations were also found between urinary 8-OHdG levels and the percentage of normal sperm morphology (ptrend Conclusions Our findings suggest that higher urinary arsenic, cadmium and lead levels were associated with increased oxidative stress markers, which also related with altered semen quality. 8-isoPGF2α and 8-OHdG might be the possible mediators of the associations between urinary heavy metals and total motility, progressive motility or the proportion of normal sperm morphology.

Pepsin plays an important role in laryngopharyngeal reflux (LPR), a risk factor for the development of hypopharyngeal squamous cell carcinomas (HPSCC). However, the role of pepsin in HPSCC is not clear. We show by immunohistochemistry that pepsin positivity occurs in a significant proportion of human primary HPSCC specimens, and in many cases matched adjacent uninvolved epithelia are negative for pepsin. Pepsin positivity is associated with nodal involvement, suggesting that pepsin may have a role in metastasis. Treatment of FaDu cancer cells with pepsin increased cell proliferation, possibly by inducing G1/S transition. We also observed significant changes in expression of genes involved in NF-kappaB, TRAIL and Notch signaling. Our data suggest that pepsin plays an important role in HPSCC and that targeting pepsin could have potential therapeutic benefits.

Background The intricate association of mortality risk with ambient air pollution and temperature is of growing concern. Little is known regarding effect of changes in season and temperature on daily cardiovascular mortality associated with air pollutant nitrogen dioxide (NO2). Objectives Our study aimed to assess the effect of NO2 on cardiovascular mortality modified by season and daily air temperature in the effect, and further to identify the population highly susceptible to cardiovascular mortality associated with NO2 and air temperature. Methods We collected daily cause-specific death data, weather conditions, and air pollutant concentrations in Shenzhen from 2013 to 2017. Distributed-lag linear models were employed to analyze the effect of season on the NO2-associated mortality. Furthermore, generalized additive models were combined with stratification parametric analysis to estimate the interaction effect of NO2 with air temperature on cardiovascular mortality. Results In the cold season, the percentage increase in daily mortality for every 10 μg/m3 increment in NO2 concentration over lags of 0–2 days was 4.45% (95% CI: 2.71–6.21%). However, no statistically significant effect of NO2 was observed in the warm season. Compared with high-temperature days (>median temperature), a 3.51% increase in mortality (95% CI: 2.04–5.01%) over low-temperature days (≤median temperature) for the same increase in NO2 was significant. Air temperature modified the effect of NO2 on daily mortality by 4.08% (95% CI: 2.28–5.91%) for the elderly (age ≥ 65 years) on low-temperature days vs. -0.82% (95% CI: −3.88–2.34%) on high-temperature days, and 3.38% (95% CI: 1.50–5.29%) for males on low-temperature days vs. -0.73% (95% CI: −3.83–2.47%) on high air temperature days. Conclusions The cold season and low temperatures could significantly enhance the effect of NO2 on cardiovascular mortality. The elderly and males suffering from cardiovascular disease should take precautions against low temperature and NO2 air pollution.

Capture of radioactive iodine has been paid much attention due to the release of radioactive iodine from nuclear accident and metal fission. Deep eutectic solvents (DESs) are green solvents. Polyethylene glycol (PEG) possesses the merits of no toxicity, high biocompatibility, high biodegradation and low cost. Here, we for the first time design a series of PEG-based DESs for efficient iodine capture. PEG:thiourea+ethanol mixture owns the highest rate and capacity for iodine capture. Effect of mass, mol ratio, organic solvent, molecular weight of PEG and composition of DESs on iodine capture is investigated. W = W∞(1 − e−kx) is first fitted for DESs to capture iodine. Conventional, difference and the PCMW2D-COS UV–Vis spectra show that PEG:thiourea+ethanol interacts with iodine mainly via halogen bonds before 75 min and via induced force after 75 min. The iodine-capturing rate by PEG:thiourea+ethanol is slightly higher than that of the reported DESs with the highest efficiency while in the same condition. Although the presence of volatile ethanol in PEG:thiourea decreases the iodine storage efficiency, it would provide a new route of improving iodine-capturing rate and capacity.

This study aimed to elucidate the protective effect of minocycline against streptomycin-induced damage of cochlear hair cells and its mechanism. Cochlear membranes were isolated from newborn Wistar rats and randomly divided into control, 500μmol/L streptomycin, 100μmol/L minocycline, and streptomycin and minocycline treatment groups. Hair cell survival was analyzed by detecting the expression of 3-nitrotyrosine (3-NT) in cochlear hair cells by immunofluorescence and an enzyme-linked immunosorbent assay. Expression of 3-NT and inducible nitric oxide synthase (iNOS), and poly (ADP-Ribose) polymerase (PARP) and caspase-3 activation were evaluated by western blotting. The results demonstrated hair cell loss at 24h after streptomycin treatment. No change was found in supporting cells of the cochleae. Minocycline pretreatment improved hair cell survival and significantly reduced the expression of iNOS and 3-NT in cochlear tissues compared with the streptomycin treatment group. PARP and caspase-3 activation was increased in the streptomycin treatment group compared with the control group, and pretreatment with minocycline decreased cleaved PARP and activated caspase-3 expression. Minocycline protected cochlear hair cells from injury caused by streptomycin in vitro. The mechanism underlying the protective effect may be associated with the inhibition of excessive formation of nitric oxide, reduction of the nitration stress reaction, and inhibition of PARP and caspase-3 activation in cochlear hair cells. Combined minocycline therapy can be applied to patients requiring streptomycin treatment.

Although the growths of ambient pollutants have been attracting public concern, the characteristic of the associations between air pollutants and mortality remains elusive. Time series analysis with a generalized additive model was performed to estimate the associations between ambient air pollutants and mortality outcomes in Shenzhen City for the period of 2012–2014. The results showed that nitrogen dioxide (NO2)-induced excess risks (ER) of total non-accidental mortality and cardiovascular mortality were significantly increased (6.05% (95% CI 3.38%, 8.78%); 6.88% (95% CI 2.98%, 10.93%), respectively) in interquartile range (IQR) increase analysis. Also, these associations were strengthened after adjusting for other pollutants. Moreover, similar associations were estimated for sulfur dioxide (SO2), particulate matter with an aerodynamic diameter of

A new layered divalent metal monohydrogenphosphate [Co(H2O) (HPO4)] · H2O (1) was hydrothermally synthesized from the reaction of CoCl2·6H2O with H3PO4 in the presence of cis-Pt(NH3)2Cl2 and ethylenediamine. The structure features extensive intra- and inter-layer hydrogen bonding among the hydrogenphosphate anion, the coordinated water and the crystallization water. X-ray crystallographic parameters for 1 are orthorhombic Pnma (#62), a = 1.7528(2), b=0.56158(7), c = 0.47867(6) nm, V = 0.47116(9) nm3, Z=4.

Small interfering RNAs (siRNA) are the latest candidates for oligonucleotide-based therapeutics. Should siRNA be successful in clinical trials, a huge demand for synthetic RNA is anticipated. We believe that 1-(4-chlorophenyl)-4-ethoxypiperidin-4-yl (Cpep) is an ideal 2'-protecting group for large-scale syntheses. Unlike 2'-silyl groups, mild acid hydrolysis instead of fluoride ion is used for the 2'-deprotection. The syntheses of 2'-Cpep protected nucleosides (A, C, G, and U) has been accomplished on a 0.5 Kg scale. The 2'-Cpep monomers were transformed into 3'-O-phosphoramidites for conventional automated solid-phase synthesis. Cost-effective processes for large-scale synthesis of Cpep monomers and initial automated solid-phase synthesis are demonstrated.

Multiple oligonucleotides of the same or different sequence, linked end-to-end in tandem can be synthesized in a single automated synthesis. A linker phosphoramidite [R. T. Pon and S. Yu (2004) Nucleic Acids Res., 32, 623–631] is added to the 5′-terminal OH end of a support-bound oligonucleotide to introduce a cleavable linkage (succinic acid plus sulfonyldiethanol) and the 3′-terminal base of the new sequence. Conventional phosphoramidites are then used for the rest of the sequence. After synthesis, treatment with ammonium hydroxide releases the oligonucleotides from the support and cleaves the linkages between each sequence. Mixtures of one oligonucleotide with both 5′- and 3′-terminal OH ends and other oligonucleotides with 5′-phosphorylated and 3′-OH ends are produced, which are deprotected and worked up as a single product. Tandem synthesis can be used to make pairs of PCR primers, sets of cooperative oligonucleotides or multiple copies of the same sequence. When tandem synthesis is used to make two self-complementary sequences, double-stranded structures spontaneously form after deprotection. Tandem synthesis of oligonucleotide chains containing up to six consecutive 20mer (120 bases total), various trinucleotide codons and primer pairs for PCR, or self-complementary strands for in situ formation of double-stranded DNA fragments has been demonstrated.

New inorganic ionic liquids (IIL) consisting of an inorganic polyoxometalate anion with the Keggin structure and a sodium cation, that is Na13[Ln(TiW11O39)2]·xH2O [where Ln = lanthanide (type 1)], Na5[MTiW11O39]·xH2O and Na6[MTiW11O39]·xH2O [where M = transition metal (type 2)], were prepared and their physicochemical properties were investigated. These ionic liquids were characterized by NMR and IR spectroscopy and by elemental analysis. Their melting point, viscosity, conductivity, thermal stability, and miscibility with water and organic solvents were determined. When the temperature is below ambient temperature (about 298 K) these ionic liquids are almost immiscible with water. When the temperature is raised, the solubility of the new ionic liquids increases sharply. The influence of the size and of the charge density of both the cations and anions on these properties was examined. The most remarkable feature of IILs is that water is their indispensable component. The role of the water molecule in ionic liquids is similar to that of crystalline water in hydrated compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

International audience; Nucleoside analogs such as 1-beta-D-arabinofuranosyl cytidine (AraC) and 2',2'-difluoro deoxycytidine (dFdC) are important components of the anticancer chemotherapeutic arsenal and are among the most effective anticancer drugs currently available. Although both AraCTP and dFdCTP impede DNA replication through pausing of DNA polymerases, both nucleoside analogs are ultimately incorporated into replicated DNA and interfere in DNA-mediated processes. Our laboratories are investigating the structural basis for the poisoning of topoisomerase I (top1) due to antipyrimidine incorporation into duplex DNA. We recently reported that both AraC and dFdC induce formation of top1 cleavage complexes, and poisoning of top1 contributes to the anticancer activities of both these drugs. Recent NMR and thermodynamic studies from our laboratories provide insight into the mechanism by which AraC and dFdC poison top1. NMR studies from our laboratories have revealed that the arabinosyl sugar of AraC adopted a C2'-endo conformation. Although this is a B-type sugar pucker characteristic of duplex DNA, the conformation is rigid, and this lack of flexibility probably contributes to inhibition of the religation step of the top1 reaction. In contrast to AraC, NMR studies revealed dFdC adopted a C3' endo sugar pucker characteristic of RNA, rather than DNA duplexes. dFdC substitution enhanced formation of top1 cleavage complexes, but did not inhibit religation. The enhancement of top1 cleavage complexes most likely results from a combination of conformational and electrostatic effects. The structural effects of dFdC and AraC are being further investigated in duplex DNA with well-defined top1 cleavage sites to analyze more specifically how these structural perturbations lead to enzyme poisoning.

More than one oligonucleotide can be synthesized at a time by linking multiple oligonucleotides end-to-end in a tandem manner on the surface of a solid-phase support. The 5'-terminal hydroxyl position of one oligonucleotide serves as the starting point for the next oligonucleotide synthesis. The two oligonucleotides are linked via a cleavable 3'-O-hydroquinone-O,O'-diacetic acid linker arm (Q-linker). The Q-linker is rapidly and efficiently coupled to the 5'-OH position of immobilized oligonucleotides using HATU, HBTU, or HCTU in the presence of 1 equiv of DMAP. This protocol avoids introduction of phosphate linkages on either the 3'- or 5'-end of oligonucleotides. A single NH(4)OH cleavage step can simultaneously release the products from the surface of the support and each other to produce free 5'- and 3'-hydroxyl termini. Selective cleavage of one oligonucleotide out of two sequences has also been accomplished via a combination of succinyl and Q-linker linker arms. Tandem synthesis of multiple oligonucleotides is useful for producing sets of primers for PCR, DNA sequencing, and other diagnostic applications as well as double-stranded oligonucleotides. Tandem synthesis of the same sequence multiple times increases the yield of material from any single synthesis column for maximum economy in large-scale synthesis. This method can also be combined with reusable solid-phase supports to further reduce the cost of oligonucleotide production.

Linker phosphoramidite reagents containing a protected nucleoside with a cleavable 3′-ester linkage to either succinic acid, diglycolic acid, or hydroquinone-O,O′-diacetic acid (Q-Linker) allow the 3′-terminal nucleoside of an oligonucleotide sequence to be attached to underivatized ‘Universal’ amino or hydroxyl supports. After solid-phase oligonucleotide synthesis, treatment with NH4OH cleaves the 3′-ester link to the support and produces oligonucleotides with only 3′-OH ends. No changes to existing phosphoramidite synthesis cycles, cleavage, or deprotection methods are required.

A general method for oligonucleotide synthesis on reusable solid-phase supports has been developed which will significantly lower the cost of large-scale synthesis. It consists of five steps: 1, nucleoside attachment to an hydroxy derivatized support through a Q-linker (hydroquinone-O,O′-diacetic acid) linker arm; 2, chloro-acetylation of unreacted surface groups; 3, conventional phosphodiester or phosphorothioate oligonucleotide synthesis; 4, cleavage from the support with aqueous or anhydrous ammonia; and 5, support regeneration with methanolic potassium carbonate. The recycling process is fast, fully automatable, and does not require removal of the support from the synthesis column. Fifteen solid-phase supports were evaluated with glycerol-CPG providing the best results. Consecutive syntheses of ISIS 2302, a dGCCCAAGCTGGCATCCGTCA phosphorothioate sequence, on the same synthesis column were performed. A glycerol-CPG synthesis column was satisfactorily used six consecutive times when NH4OH was the cleavage reagent. However, anhydrous NH3 allowed twelve consecutive syntheses without any deterioration in support loading, product quality, or amount of product produced. An improved method for preparing the essential nucleoside-3′-hemiesters of the Q-Linker and an unexpectedly slower rate of cleavage for phosphorothioate DNA vs. phosphodiester DNA are also described.

Multiple oligonucleotides linked end-to-end in tandem can be synthesized by adding a nucleoside to the 5'-OH end of a prior sequence. Nucleosides with 3'-succinyl or Q-Linker arms are coupled with HBTU/DMAP. Alternatively, new phosphoramidite reagents with 3'-ester linkages can be used. Hydroxyl or amino supports can also be used as universal starting materials. Treatment with NH4OH cleaves the 3'-ester to yield only 3'-OH groups and no unwanted 3'-phosphorylated products occur.

A novel combinatorial approach to synthesize oligonucleotides on fluorescently encoded microspheres based on flow sorting and segmental solid-phase synthesis is described. BODIPY dyes were covalently attached to polystyrene (8.8 microm, 55% DVB) microsphere particles to generate four fluorescently encoded sets. 20-mer oligonucleotide sequences can be synthesized on these microspheres with yields comparable to conventional CPG supports (80% overall yield, average stepwise yield = 99%). The concept of segmental solid-phase synthesis by flow sorting was demonstrated by synthesizing unique 20-mer oligonucleotide sequences on each of four fluorescently encoded microsphere sets by including a flow sorting step (after first eight base additions) and flow cytometric detection of sequences synthesized on each microsphere set by hybridization with fluorescently labeled complementary sequence.

A new method for the preparation of 3,4- and 2,5-disubstituted furan rings is described. A variety of 2-silylated-3-(hydroxymethyl)furans and 2-silylated-3-furoic acids lithiate exclusively at C-4 when treated with 2.2 equivs of BuLi. The resulting dianions were quenched with a variety of electrophiles to provide 2-silylated-3-(hydroxymethyl)-4-substituted furans and 2-silylated-4-substituted 3-furoic acids in good to excellent yields. Removal of the silyl group (n-Bu4NF) provided a variety of 4-substituted-3-(hydroxymethyl)furans and methyl 4-substituted-3-furoates, respectively. The latter esters were prepared due to difficulties encountered in isolating 4-substituted-3-furoic acids. The site of lithiation was altered by protecting the 3-hydroxyl group with a triethylsilane. Lithiation of 2-silylated-3-(((triethylsilyl)oxy)methyl)furan with 1.2 equivs of BuLi followed by the addition of electrophiles provided 2-silylated-3-(((triethylsilyl)oxy)methyl)-5-substituted furan rings. Subsequent removal of bot...

Very fast (4 sec) attachment of nucleosides to CPG supports, via succinyl or QDA linkers, is possible with either uronium (HBTU, HATU, HBPyU, HBPipU) or phosphonium (BOP, PyBOP ® , PyBroP, BroP) coupling reagents and automated derivatization of CPG and polystyrene supports just prior to oligonucleotide synthesis has been demonstrated.

Hydroquinone-O,O′-diacetic acid (QDA) can be used to link nucleosides to CPG or polystyrene supports instead of succinic acid. Cleavage of oligodeoxy- or oligoribonucleotides, using ammonium hydroxide, requires only two to five minutes. The QDA linker is stable, easily prepared and does not require any other changes to the reagents, methods, or instrumentation used in automated solid-phase oligonucleotide synthesis.

2-(tert-Butyldimethylsilyl)-3-furoic acid 7 was regiospecifically lithiated at the C-4 position when treated with 2.5 equiv. of butyllithium (at –20 °C) in either tetrahydrofuran or 1,2-dimethoxyethane; trapping of the dianion with a variety of electrophiles provided 2,3,4-trisubstituted furans in good to excellent yield.

An improved preparation of various 2-substituted-3-furoic acids by lithiation of 2-methyl-3-furoic acid with 2.0 equiv. of butyllithium, and a successful intramolecular Diels–Alder reaction using 0.1 equiv. of methylaluminium dichloride between a dienophile and furan diene, which are both substituted with an electron withdrawing moiety, are described.

New linker phosphoramidite reagents containing a cleavable 3'-ester linkage are used for attaching the first nucleoside to the surface of a solid- phase support. Inexpensive, underivatized amino supports, such as long chain alkylamine controlled-pore glass, can serve as universal supports. No modifications to phosphoramidite coupling conditions are required and, after synthesis, treatment with NH(4)OH releases the products with 3'-OH ends. No 3'-dephosphorylation is required. Phosphoramidite reagents containing a succinate and sulfonyl diethanol linkage between the nucleoside and phosphoramidite group are particularly advantageous and can be used to create both 3'-OH and 5'-phosphate ends on oligonucleotides. Reproducibility and quality of oligonucleotide synthesis is demonstrated for either column and 96-well plate formats on low-, medium- or high-loading CPG supports.

First Base™ linker phosphoramidites add the first nucleoside to underivatized solid-phase supports using a regular phosphoramidite coupling cycle. A cleavable 3'-0-ester linkage allows NH4OH treatment to rapidly generate products with only 3'-OH ends. Either single or multiple sequences linked in tandem can be prepared and no additional deprotection steps are required.

An improved preparation of various 2-substituted-3-furoic acids by lithiation of 2-methyl-3-furoic acid with 2.0 equiv. of butyllithium, and a successful intramolecular Diels–Alder reaction using 0.1 equiv. of methylaluminium dichloride between a dienophile and furan diene, which are both substituted with an electron withdrawing moiety, are described.

Nucleosides can be esterified to solid-phase supports using uronium or phosphonium coupling reagents and a coupling additive, such as 1-hydroxybenzotriazole (HOBT), 7-aza-1-hydroxybenzotriazole (HOAT), N-methylimidazole (NMI), or 4-(dimethylamino)pyridine (DMAP). However, DMAP was far superior to other additives and high nucleoside loadings (up to 60 micromol/g) and rapid coupling reactions (or = 10 min) were possible. Hydroxyl-derivatized CPG was attached to nucleosides with 3'-succinyl or 3'-hydroquinone-O, O'-diacetic acid (HQDA or Q-Linker) carboxyl groups through a primary ester linkage. Alternatively, supports derivatized with succinic acid or the Q-Linker were attached directly to the 3'-OH group of nucleosides through a secondary ester linkage. Uronium reagents (HATU or HBTU) gave the best results with the HQDA linker arm, while the bromophosphonium (BrOP or PyBrOP) reagents were best with the succinyl linker arm. In all cases, the coupling reactions were much faster than previous methods using carbodiimide coupling reagents. The ease and speed of the reaction make this support derivatization procedure suitable for automated in situ couplings on DNA synthesizers.

A strategy for oligodeoxyribonucleotide synthesis on a reusable CPG solid-phase support, derivatized with hydroxyl groups instead of amino groups, has been developed. Ester linkages, through a base labile hydroquinone- O, O '-diacetic acid ( Q-Linker ) linker arm, were used to couple the first nucleoside to the hydroxyl groups on the support. This coupling was rapidly accomplished (10 min) using O -benzotriazol-1-yl- N, N, N ', N '-tetramethyluronium hexafluorophosphate (HBTU) and 1-hydroxybenzotriazole as the activating reagents. Oligodeoxyribonucleotide synthesis was performed using existing procedures and reagents, except a more labile capping reagent, such as chloro-acetic anhydride, methoxyacetic anhydride or t-butylphenoxyacetic anhydride, was used instead of acetic anhydride. After each oligodeoxyribonucleotide synthesis, the product was cleaved from the support with ammonium hydroxide (3 min) and deprotected as usual. Residual linker arms or capping groups were removed by treatment with ammonium hydroxide/methylamine reagent and the regenerated support was capable of reuse. Up to six different oligodeoxyribonucleotide syntheses or up to 25 cycles of nucleoside derivatization and cleavage were consecutively performed on the reusable support. This method may provide a significant cost advantage over conventional single-use solid supports currently used for the manufacture of antisense oligodeoxyribonucleotides.

When hydroquinone-O,Ooffiacetic acid is used as a linker arm in solid phase oligonucleotide synthesis, the time for NH4OH cleavage of oligodeoxy- or oligoribonucleotides is reduced to only 2 min. This allows increased productivity on automated DNA synthesizers without requiring any other modifications to existing reagents or synthesis and deprotection methods. The Q-linker may also be rapidly cleaved by milder reagents such as 5% NH4OH, potassium carbonate, anhydrous ammonia, t-butylamine or fluoride ion. However, the Q-linker is sufficiently stable for long-term storage at room temperature without degradation and no loss of material occurs during synthesis. The linker is also reasonably resistant to 20% piperidine/DMF, 0.5 M DBU/pyridine and 1:1 triethylamine/ethanol. The Q-linker can therefore serve as a general replacement for both succinyl and oxalyl linker arms.

Reusable solid-phase supports for large scale oligonucleotide synthesis have been prepared by converting amino derivatized supports into hydroxyl supports. Rapid nucleo side attachment, via a Q-linker arm, was automatically performed on the DNA synthesizer using HBTU and DMAP as the coupling reagents. All steps were suitable for automation and ∼ 1.5 h was required to prepare the supports for reuse. Up to twelve consecutive syntheses of a 20-mer phosphorothioate were performed on a synthesis column.

2-(tert-Butyldimethylsilyl)-3-furoic acid 7 was regiospecifically lithiated at the C-4 position when treated with 2.5 equiv. of butyllithium (at –20 °C) in either tetrahydrofuran or 1,2-dimethoxyethane; trapping of the dianion with a variety of electrophiles provided 2,3,4-trisubstituted furans in good to excellent yield.