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PubMed1990

A novel carbodiimide coupling method for synthetic peptides. Enhanced anti-peptide antibody responses.

Coupling of peptides to immunogenic protein carriers is required for the generation of anti-peptide antibody responses. Carbodiimides are hetero bi-functional coupling reagents that are utilized for coupling reactions through carboxyl and amino groups. The procedures generally used for carbodiimide coupling of peptides and proteins result in conjugates which generate immunodominant antibody responses directed against the neodeterminants on the carrier protein. These determinants are induced by the reaction of carrier and/or peptide with the coupling agent. We have investigated the potential inhibiting effect of an imidazole intermediary on the formation of unwanted neodeterminants during carbodiimide coupling. The serum antibody responses elicited with the peptide-protein conjugates produced were evaluated in ELISA. We have modified and improved the coupling with a watersoluble carbodiimide (EDC) in such a way that a high response to the coupled peptide is obtained in association with negligible levels of anti-neodeterminant antibodies.

Amino Acid Sequence↗

PubMed1992

Regulation of transcription by translational components in coupled translation-transcription cell-free system.

A coupled translation-transcription cell-free system was established from eukaryotic cells. The biosynthetic activity of this coupled system closely resembles the synthetic behavior of cells in vivo, and exhibits regulatory phenomena similar to that of intact cells. The translational system consists of rabbit reticulocyte lysate, or its components fractionated by centrifugation. The transcriptional portion consists of cockerel liver nuclei. Incorporation of amino acids into protein by the coupled system is linear for hours. Similarly, transcription in the coupled system is continuous for hours and is proportional with time. More than 90% of the transcriptional products are secreted into the incubation medium. The components of the translational system influence and regulate transcriptional activities. In the presence of ribosomes the nuclei transcribe mostly poly(A)+ RNA with alpha-amanitin sensitivity consistent with activation of RNA polymerase II. Hybrid selection experiments demonstrate authentic preproalbumin mRNA among the transcriptional products. The putative mRNA secreted into the medium in the coupled system is found on polysomes, indicating translation of de novo synthesized message. Addition of excess reticulocyte mRNP to the medium of the coupled system results in transcription of primarily ribosomal RNA, 5S RNA, and tRNA, the products of RNA polymerases I and III. These activities closely imitate the behavior of liver in vivo under conditions of nutritional shifts or hormonal influences. The coupled system transcribes, processes, and transports substantial quantities of RNA, about 1.6 micrograms/10(6) nuclei/h. Thus, a coupled system has been established that lends itself to the exploration of regulatory interactions of cell components as it appears to closely resemble the in vivo situation.

Animals↗

PubMed1984

A minimal hypothesis for membrane-linked free-energy transduction. The role of independent, small coupling units.

Experimental data are reviewed that are not in keeping with the scheme of 'delocalized' protonic coupling in membrane-linked free-energy transduction. It turns out that there are three main types of anomalies: (i) rates of electron transfer and of ATP synthesis do not solely depend on their own driving force and on delta mu H, (ii) the ('static head') ratio of delta Gp to delta mu H varies with delta mu H and (iii) inhibition of either some of the electron-transfer chains or some of the H+-ATPases, does not cause an overcapacity in the other, non-inhibited proton pumps. None of the earlier free-energy coupling schemes, alternative to delocalized protonic coupling, can account for these three anomalies. We propose to add a fifth postulate, namely that of the coupling unit, to the four existing postulates of 'delocalized protonic coupling' and show that, with this postulate, protonic coupling can again account for most experimental observations. We also discuss: (i) how experimental data that might seem to be at odds with the 'coupling unit' hypothesis can be accounted for and (ii) the problem of the spatial arrangement of the electrical field in the different free-energy coupling schemes.

ATP Synthetase Complexes↗

PubMed1987

Dye coupling among supraoptic nucleus neurons without dendritic damage: differential incidence in nursing mother and virgin rats.

To assess the possibility that dye coupling among neurons in hypothalamic slices might require dendrotomy, as has been suggested for neocortical neurons, dye coupling was studied in horizontally cut slices containing the supraoptic nucleus (SON). Since the dendrites of SON neurons project toward the pial surface, dendritic damage due to slicing can be avoided in the horizontal plane. Intracellular injections of Lucifer Yellow into individual SON neurons in slices from male, virgin female and lactating, mother rats yielded the following results. When dendrotomy occurred there was a significantly lower incidence of dye coupling than was observed when dendrites were intact. Higher order coupling (3 or more cells dye coupled after a single injection) was only seen among neurons without dendrotomy. Independently of dendritic damage, incidence of dye coupling in nursing mothers was reliably greater than for virgins, confirming previous results from coronal slices. The results of this study indicate that dendrotomy is not an inducer of dye coupling in SON neurons. Taken together with other recent findings, these data suggest that a reinterpretation of the effects of dendrotomy on cortical cell dye coupling may be in order.

Animals↗

PubMed2004

Late porous polyethylene implant exposure after motility coupling post placement.

PURPOSE: To report the probable association of motility coupling post placement and late porous polyethylene implant exposure. DESIGN: Retrospective, observational case series. METHODS: This was a retrospective analysis of 27 patients who had primary porous polyethylene orbital implantation from February 1999 to November 2000. Data on demographics, previous surgery, ocular diagnosis, type of surgery, size of the implant, and motility coupling post placement were collected. Complications of porous polyethylene implants and implant exposure were documented. RESULTS: Among the 27 patients, 18 eyes (66.7%) received motility coupling post insertion after primary porous polyethylene implantation. Implant exposure occurred in six (33.3%) of the 18 eyes with motility coupling post insertion. None of the eyes without insertion had implant exposure. The mean interval between porous polyethylene implantation and motility coupling post placement for the implant exposure group (6 of 18) was 6.5 +/- 0.4 months, which was not statistically significant compared with 7.2 +/- 0.6 months in the nonexposure group (12 of 18). For these 6 cases of implant exposure, the mean interval between implantation and implant exposure was 24.2 +/- 11.8 months, and the mean interval between pegging and exposure was 17.6 +/- 11.7 months. Among these 6 patients, 4 underwent removal of exposed porous polyethylene implants and reimplantation of hydroxyapatite implant or dermis fat reconstruction. CONCLUSIONS: We found a trend (P =.07) of increasing risk of porous polyethylene implant exposure with motility coupling post placement. Although the pegging group did not show a statistically significant higher rate of exposure compared with the nonpegging group, we believe that more care was needed when performing motility coupling post placement. In addition, longer postoperative follow-up is needed after insertion of a motility coupling post.

Adolescent↗

PubMed2004

Lower extremity joint coupling during running: a current update.

BACKGROUND: The relationship between lower extremity mechanics and injury is not well understood. However, joint coupling studies are beginning to emerge, which may lend further insight into running biomechanics. PURPOSE: To provide a current review of the research examining lower extremity joint coupling in running. SUMMARY: There are various techniques utilized to measure joint coupling, including joint timing, rearfoot eversion/tibial internal rotation ratios, continuous relative phase calculations, and vector coding. The study of joint coupling is of particular interest as it may pertain to running injuries. There is some evidence that joint coupling may be altered with orthotics and/or with footwear. Most studies have included a relatively small sample size and larger scale studies are needed to quantify normal ranges for many of the coupling measures. In addition, prospective studies are needed to clarify the relationship to injury. RELEVANCE: It is hoped that this update will serve as a review of the current state of thought regarding lower extremity joint coupling during running. As greater insight into the role of joint coupling in injuries is gained, more optimal intervention and prevention strategies can be developed to minimize injury risk.

Ankle Joint↗

PubMed2005

Coupled bilateral movements and active neuromuscular stimulation: intralimb transfer evidence during bimanual aiming.

Motor improvements in chronic stroke recovery accrue from coupled protocols of bilateral movements and active neuromuscular stimulation. This experiment investigated coupled protocols and within-limb transfer between distal and proximal joint combinations. The leading question focused on within-limb transfer of coupled protocols on distal joints to a bimanual aiming task that involved proximal joints. Twenty-six volunteers completed one of three motor recovery protocols according to group assignments: (1) coupled bilateral involved concurrent wrist/finger movements on the unimpaired limb coupled with active stimulation on the impaired limb; (2) unilateral/active stimulation involved neuromuscular electromyogram-triggered stimulation on the impaired wrist/fingers; and (3) no protocol (control group). During the pretest and posttest, subjects performed transverse plane target aiming movements (29 cm) with vision available. The coupled bilateral group showed positive intralimb transfer post-treatment when both arms moved simultaneously. During the posttest, the coupled bilateral group displayed improved movement time, higher peak limb velocity, less variability in peak velocity, and less percentage of total movement time in the deceleration phase than during the pretest. The evidence confirms that within-limb transfer from distal joint training to proximal joint combinations is viable and generalizable in chronic stroke rehabilitation. Moreover, these intralimb transfer findings extend the evidence favoring motor improvements for coupled bilateral protocols during chronic stroke.

Electric Stimulation Therapy↗

PubMed2003

A cell-based microarrayed compound screening format for identifying agonists of G-protein-coupled receptors.

The identification of agonist and antagonist leads for G-protein-coupled receptors (GPCRs) is of critical importance to the pharmaceutical and biotechnology industries. We report on the utilization of a novel, high-density, well-less screening platform known as microarrayed compound screening microARCS) that tests 8640 compounds in the footprint of a standard microtiter plate for the identification of novel agonists for a specific G-protein-coupled receptor. Although receptors coupled to the G alpha(q) protein can readily be assessed by fluorescence-based Ca(2+) release measurements, many GPCRs that are coupled to G alpha(s) or G alpha(i/o) proteins are not amenable to functional evaluation in such a high-throughput manner. In this study, the human dopamine D(4.4) receptor, which normally couples through the G alpha(i/o) protein to inhibit adenylate cyclase and to reduce levels of intracellular cAMP, was coupled to intracellular Ca(2+) release by stably coexpressing this receptor with a chimeric G(alpha qo5) protein in HEK-293 cells. In microARCS format, the cells expressing D(4.4) receptor and G alpha(qo5) protein were preloaded with fluo-4, cast into a 1% agarose gel, placed above the compound sheets, and imaged successively using a ViewLux charge-coupled device imaging system. Dopamine and other agonists evoked an increase in fluorescence response that appeared as bright spots in a time- and concentration-dependent manner. Utilizing this technology, a library of 260,000 compounds was rapidly screened and led to the identification of several novel agonists. These agonists were further characterized using a fluorometric imaging plate reader assay. Excellent confirmation rates coupled with enhanced efficiency and throughput enable microARCS to serve as an alternative platform for the screening and identification of novel GPCR agonists.

Apomorphine↗

PubMed2003

Ca2+-dependent excitation-contraction coupling triggered by the heterologous cardiac/brain DHPR beta2a-subunit in skeletal myotubes.

Molecular determinants essential for skeletal-type excitation-contraction (EC) coupling have been described in the cytosolic loops of the dihydropyridine receptor (DHPR) alpha1S pore subunit and in the carboxyl terminus of the skeletal-specific DHPR beta1a-subunit. It is unknown whether EC coupling domains present in the beta-subunit influence those present in the pore subunit or if they act independent of each other. To address this question, we investigated the EC coupling signal that is generated when the endogenous DHPR pore subunit alpha1S is paired with the heterologous heart/brain DHPR beta2a-subunit. Studies were conducted in primary cultured myotubes from beta1 knockout (KO), ryanodine receptor type 1 (RyR1) KO, ryanodine receptor type 3 (RyR3) KO, and double RyR1/RyR3 KO mice under voltage clamp with simultaneous monitoring of confocal fluo-4 fluorescence. The beta2a-mediated Ca2+ current recovered in beta1 KO myotubes lacking the endogenous DHPR beta1a-subunit verified formation of the alpha1S/beta1a pair. In myotube genotypes which express no or low-density L-type Ca2+ currents, namely beta1 KO and RyR1 KO, beta2a overexpression recovered a wild-type density of nifedipine-sensitive Ca2+ currents with a slow activation kinetics typical of skeletal myotubes. Concurrent with Ca2+ current recovery, there was a drastic reduction of voltage-dependent, skeletal-type EC coupling and emergence of Ca2+ transients triggered by the Ca2+ current. A comparison of beta2a overexpression in RyR3 KO, RyR1 KO, and double RyR1/RyR3 KO myotubes concluded that both RyR1 and RyR3 isoforms participated in Ca2+-dependent Ca2+ release triggered by the beta2a-subunit. In beta1 KO and RyR1 KO myotubes, the Ca2+-dependent EC coupling promoted by beta2a overexpression had the following characteristics: 1), L-type Ca2+ currents had a wild-type density; 2), Ca2+ transients activated much slower than controls overexpressing beta1a, and the rate of fluorescence increase was consistent with the activation kinetics of the Ca2+ current; 3), the voltage dependence of the Ca2+ transient was bell-shaped and the maximum was centered at approximately +30 mV, consistent with the voltage dependence of the Ca2+ current; and 4), Ca2+ currents and Ca2+ transients were fully blocked by nifedipine. The loss in voltage-dependent EC coupling promoted by beta2a was inferred by the drastic reduction in maximal Ca2+ fluorescence at large positive potentials (DeltaF/Fmax) in double dysgenic/beta1 KO myotubes overexpressing the pore mutant alpha1S (E1014K) and beta2a. The data indicate that beta2a, upon interaction with the skeletal pore subunit alpha1S, overrides critical EC coupling determinants present in alpha1S. We propose that the alpha1S/beta pair, and not the alpha1S-subunit alone, controls the EC coupling signal in skeletal muscle.

Alleles↗

PubMed1983

Frequency domain analysis of electrotonic coupling between leech Retzius cells.

Transfer functions of the input impedance Z(f) and coupling ratio H(f) were measured from the paired Retzius cells of leech segmental ganglia, using sinusoidal and pseudorandom test test currents. The data were compared with two classes of linear electric circuit models of electrotonic coupling, one with a purely resistive junction, and the other with a finite equivalent cable coupling the two somata. Model simulations suggested the phase behavior of the coupling ratio as a sensitive discriminator between these two cases. For resistive coupling, the phase of the coupling ratio asymptotically approaches -90 degrees at high frequencies, while for a cable segment, at least 0.5 length constants in length, it crosses -90 degrees with a definite negative slope and continues to more negative values. Measured phase lags of the coupling ratio in Retzius cell preparations consistently exceeded -90 degrees at frequencies above 50 Hz, and phase plots crossed -90 degrees with significantly negative slopes. We conclude therefore that a significant cable segment contributes to the coupling between Retzius cell somata.

Animals↗

PubMed2002

Histamine H1-receptor modulation of inter-neuronal coupling among vasopressinergic neurons depends on nitric oxide synthase activation.

Inter-neuronal coupling is a relatively recently documented property of a wide variety of cell groups in the mammalian central nervous system. For many of these groups there is evidence that the coupling can be modulated by synaptic inputs. Incidence of dye coupling among vasopressin (VP) neurons of the rat supraoptic nucleus (SON) has been shown to increase in response to either activation of histamine H(1)-receptors or to increased NO production. Both of these effects involve activation of cGMP-dependent pathways. We tested the hypothesis that activation of H(1)-receptors resulted in downstream activation of NO synthase, which then mediated the H(1)-receptor effects. Putative VP neurons were intracellularly recorded and dye-injected in horizontal slices of hypothalamus, in which monosynaptic connections from the tuberomammillary nucleus (TM) were intact and electrically stimulated. Single-pulse TM stimulation evoked EPSPs and repetitive stimulation resulted in a nearly 3-fold increase in coupling incidence over unstimulated slices. TM-stimulated increased coupling was completely blocked by inhibitors of NO synthase (L-NAME) or of soluble guanylyl cyclase (ODQ or methylene blue), or pyrilamine, suggesting that the H(1)-receptor is not directly linked to guanylyl cyclase. Addition of the NO precursor, L-arginine or the NO donor, SNP, in combination with TM stimulation produced increases in coupling that were not significantly larger than those seen with stimulation alone, supporting the idea that a common pathway was used. We conclude that H(1)-receptors activate NO synthase via G-protein-coupled pathways and that NO working though its receptor, induces the downstream cGMP-dependent processes that result in increased inter-neuronal coupling.

Animals↗

PubMed2003

Benzodiazepine agonist and inverse agonist coupling in GABAA receptors antagonized by increased atmospheric pressure.

Past work found that exposure to 12 times normal atmospheric pressure (ATA) of helium-oxygen gas (heliox) selectively antagonizes (uncouples) and differentiates allosteric coupling in GABA(A) receptors initiated by benzodiazepines versus neurosteroids. The present study tested the hypothesis that pressure can differentiate coupling initiated by a spectrum of benzodiazepine receptor ligands by measuring the effects of pressure on benzodiazepine ligand modulation of GABA-activated 36Cl(-) uptake in mouse brain membranes. 12 ATA completely antagonized allosteric modulation by: benzodiazepine receptor agonists diazepam and flunitrazepam; Type-1 selective benzodiazepine receptor agonist zolpidem and the benzodiazepine receptor partial inverse agonist ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-alpha][1,4]benzodiazepine-3-carboxylate (Ro15-4513). The similar, non-competitive-like characteristics of pressure antagonism of these ligands suggest common structural/functional elements underlying their coupling. Pressure also antagonized allosteric modulation by the benzodiazepine receptor inverse agonist methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), but the antagonism was not complete and appeared to be surmountable (competitive-like) suggesting unexpected differences in coupling for DMCM versus Ro15-4513. These studies represent the first attempt to use pressure as a tool to dissect benzodiazepine receptor coupling. The results suggest that there is a common, pressure antagonism sensitive structural/functional element underlying coupling for benzodiazepine receptor ligands and that coupling for the full inverse benzodiazepine receptor agonist DMCM differs from coupling for benzodiazepine receptor agonists and benzodiazepine receptor partial inverse agonists.

Animals↗

PubMed2001

Cost-effectiveness of hysterosalpingography, laparoscopy, and Chlamydia antibody testing in subfertile couples.

OBJECTIVE: To evaluate the cost-effectiveness analysis of hysterosalpingography (HSG), laparoscopy, and Chlamydia antibody testing (CAT) in subfertile couples. DESIGN: Cost-effectiveness analysis. SETTING: Decision analytic framework. PATIENT(S): Data of >2,000 subfertile couples in the Canadian Infertility Treatment Evaluation Study. Results of CA-125 measurement and CAT were simulated from baseline characteristics. INTERVENTION(S): Expectant management was considered to be the reference strategy (strategy 1). In strategy 2 and 3, IVF was offered either immediately or after 2.5 years. In strategy 4, the decision to offer or delay treatment was based on the couple's chance of spontaneous conception. Nine strategies incorporated combinations of CAT, CA-125 measurement, HSG, and laparoscopy. MAIN OUTCOME MEASURE(S): Expected live birth rates, expected number of IVF cycles, and expected total costs. RESULT(S): The strategy starting with CAT was the most cost-effective in couples whose 3-year chance of conception was >14%, whereas the strategy starting with HSG was the most cost-effective in couples with worse fertility prospects. CONCLUSION(S): The diagnostic work-up to detect tubal pathology in subfertile couples should start with CAT in couples with relatively good fertility prospects and immediate HSG in couples with relatively poor fertility prospects.

Adult↗

PubMed1994

Outcome of donor versus husband insemination in couples with unexplained infertility treated by in vitro fertilization and embryo transfer.

OBJECTIVE: To examine the IVF-ET outcome of couples with unexplained infertility treated by husband versus donor sperm. DESIGN: A retrospective analysis of the IVF-ET outcome of couples with unexplained infertility treated by either husband or donor sperm and in a subgroup of patients treated simultaneously by husband and donor sperm. SETTING: IVF Unit, Serlin Maternity Hospital, Tel Aviv, Israel. PATIENTS: Couples diagnosed as having unexplained infertility underwent IVF at our Unit; included were 96 couples treated by husband insemination (group A), 27 couples who received donor insemination because of azoospermia (group B), and 8 couples who sought donor insemination after having previously failed IVF (group C). RESULTS: No statistically significant difference was found between groups A and B regarding age of the females, duration of infertility, number of IVF cycles, fertilization rate, number of ETs, and pregnancy rate. Oocytes collected in group C were subdivided further into two groups: 45 were incubated with husband sperm and 46 were incubated with donor sperm. Fertilization rates were 46.6% and 50%, respectively. One pregnancy occurred. CONCLUSION: In couples with unexplained infertility who had undergone IVF-ET with husband insemination, the fertilization and pregnancy rates were similar to those of couples who were treated by donor sperm.

Adult↗

PubMed1997

Neuronal dye coupling in the developing rat fascia dentata.

The present study describes dye coupling among neurons of the developing rat fascia dentata following impalement and intracellular filling with Neurobiotin. The number of neuronal impalements resulting in dye-coupled cells decreases from P14 to P120. The most rapid decline in dye coupling was observed between P14 and P21, the beginning of the most active period of synaptogenesis in the dentate molecular layer. Dye coupling between granule cells and axo-axonic interneurons (chandelier cells) accounts for about 10% of the dye-coupled neuronal population acquired in slices from P14 and P21 rats and declines to less than 5% by P60 and P120. Our data suggest that dye coupling is related reciprocally to the number of synapses formed on granule cells. Thus the relationship of dye coupling to synaptic density in the developing fascia dentata is similar to that reported in studies of the aging fascia dentata. Also the observation of axo-axonic interneurons coupled to granule cells at all ages suggests an interesting neuronal arrangement with the potential of limiting granule cell discharge to discrete neuronal assemblies in response to perforant path input.

Aging↗

PubMed2000

Neighborhood poverty as a predictor of intimate partner violence among White, Black, and Hispanic couples in the United States: a multilevel analysis.

PURPOSE: This study assessed the contribution of neighborhood poverty, measured at the census tract level, to the risk of male-to-female and female-to-male partner violence (MFPV, FMPV) among white, black, and Hispanic couples in the United States. METHODS: As part of the 1995 National Alcohol Survey, a representative sample of married/cohabiting couples was obtained through a multistage, multicluster household probability sampling frame. The outcome variables, MFPV and FMPV, were measured through the Conflict Tactics Scale, Form R. Sociodemographic, psychosocial, and alcohol consumption covariates that were statistically significant through bivariate analysis were retained as individual-level predictors. Neighborhood poverty, indicating residence in a census tract where greater than 20% of the population lived below the Federal poverty line, was assessed by appending 1990 Census data to the primary data set. Multilevel logistic regression models were constructed, with separate analyses performed for each outcome (MFPV, FMPV) among the white, black, and Hispanic couples. RESULTS: Couples residing in impoverished neighborhoods are at increased risk for both MFPV and FMPV. The association between residence in an impoverished neighborhood and MFPV was statistically significant for black couples (Odds Ratio [OR] 2.87; 95% Confidence Interval [CI] 1.36, 6.07). The association between residence in an impoverished neighborhood and FMPV was statistically significant for black couples and white couples. CONCLUSIONS: Characteristics of the socioenvironment, such as neighborhood poverty, are associated with the risk of partner violence, particularly among black couples. Policies aimed at reducing community poverty may contribute to effective partner violence prevention strategies.

Black or African American↗

PubMedDate not supplied

Coupling pattern of S1 and S2 amacrine cells in the rabbit retina.

Previous studies have shown that indoleamine-accumulating cells (IACs) in the rabbit retina consist of two main cell types: S1 and S2 amacrine cells (Vaney, 1986; Sandell & Masland, 1986). Both cell types are wide-field GABA amacrine cells that make reciprocal synaptic contacts with rod bipolar cell terminals (Ehinger & Holmgren, 1979; Strettoi et al., 1990). We have examined the coupling pattern of S1 and S2 amacrine cells after the intracellular injection of Neurobiotin. Our results may be summarized as follows: (1) S1 amacrine cells were extensively coupled and their dendrites formed a network similar to but less dense than the matrix stained with an antibody to serotonin. (2) Morphological observations and cluster analysis, based on a scattergram, showed that the vast majority of coupled cells were S1 amacrine cells, accounting for approximately half of the total IACs. The rest of the uncoupled IACs were S2 amacrine cells. (3) Sometimes, two adjacent varicosities, one from an injected S1 and one from a coupled S1, contacted a single rod bipolar terminal. (4) S2 amacrine cells were also coupled but much less than the S1s. (5) Rarely, crossover coupling between S1 and S2 amacrine cells was observed. These results suggest that the extensive coupling between S1 amacrine cells, combined with a larger dendritic field, may contribute a wide-field component to the inhibitory surround of the rod pathway. By comparison, the smaller, weakly coupled S2 amacrine cells may provide a local component.

Amacrine Cells↗

PubMed2001

Diversity-oriented synthesis of multisubstituted olefins through the sequential integration of palladium-catalyzed cross-coupling reactions. 2-pyridyldimethyl(vinyl)silane as a versatile platform for olefin synthesis.

A novel strategy for the diversity-oriented synthesis of multisubstituted olefins, where 2-pyridyldimethyl(vinyl)silane functions as a versatile platform for olefin synthesis, is described. The palladium-catalyzed Heck-type coupling of 2-pyridyldimethyl(vinyl)silanes with organic iodides took place in the presence of Pd2(dba)3/tri-2-furylphosphine catalyst to give beta-substituted vinylsilanes in excellent yields. The Heck-type coupling occurred even with alpha- and beta-substituted 2-pyridyldimethyl(vinyl)silanes. The one-pot double Heck coupling of 2-pyridyldimethyl(vinyl)silane took place with two different aryl iodides to afford beta,beta-diarylated vinylsilanes in good yields. The palladium-catalyzed Hiyama-type coupling of 2-pyridyldimethyl(vinyl)silane with organic halides took place in the presence of tetrabutylammonium fluoride to give di- and trisubstituted olefins in high yields. The sequential integration of Heck-type (or double Heck) coupling and Hiyama-type coupling produced the multisubstituted olefins in regioselective, stereoselective, and diversity-oriented fashions. Especially, the one-pot sequential Heck/Hiyama coupling reaction provides an extremely facile entry into a diverse range of stereodefined multisubstituted olefins. Mechanistic considerations of both Heck-type and Hiyama-type coupling reactions are also described.

Alkenes↗