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4 results on '"Riccardo S"'

1. Decarboxylative radical additions to vinyl boronic esters

Author

Mega, Riccardo S. and Aggarwal, Varinder

Abstract

This thesis details the development of novel decarboxylative radical addition reactions to vinyl boronic esters using photoredox catalysis, enabling the efficient and rapid access of functionalised alkyl boronic esters from abundant feedstock chemicals. Key to the success of these methodologies is the stabilised α-boryl radical intermediate generated upon radical addition to the vinyl boronic ester, which can undergo a range of terminating events to yield a diverse library of complex boronic ester products. Firstly, the decarboxylative radical addition reaction of carboxylic acids to vinyl boronic esters was developed to directly access alkyl boronic esters using photoredox catalysis. The reaction was applied to a range of carboxylic acids, including α-amino, α-oxy and alkyl acids providing the corresponding boronic ester products in good to excellent yields. Moreover, the reaction could be applied to a range of substituted vinyl boronic esters. Mechanistic studies confirmed a radical-polar crossover mechanism, involving an unprecedented single-electron reduction of the α-boryl radical to the corresponding α-boryl anion, which is subsequently protonated. Having set the stage for photoredox-mediated decarboxylative radical additions to vinyl boronic esters, we demonstrated that we could trap the α-boryl anion with an electrophile tethered to the vinyl boronic ester, enabling the synthesis of highly functionalised, polysubstituted cyclopropyl boronic esters. Mechanistic studies supported a radical-polar crossover mechanism involving an intramolecular SN2 cyclisation to yield the cyclopropane. Finally, to introduce further molecular complexity into these molecules, a decarboxylative conjunctive cross-coupling of vinyl boronic esters with carboxylic acids and aryl iodides using metallaphotoredox catalysis was developed. Trapping of the intermediate α-boryl radical with an aryl nickel complex enabled a cross-coupling event to yield complex benzylic boronic ester products. A range of α-amino acids, mainly secondary amino acids, and tertiary α-oxy acids with aryl iodides were successfully employed and the methodology was applied to the synthesis of four sedum alkaloid natural products.

Published
2020

2. Geographical contrasts of Y-chromosomal haplogroups from wild and domestic goats reveal ancient migrations and recent introgressions

Author

Nijman, I. J., Rosen, B. D., Bardou, P., Faraut, T., Cumer, T., Daly, K. G., Zheng, Z., Cai, Y., Asadollahpour, H., Kul, B. C., Zhang, W. -Y., Guangxin, E., Ayin, A., Baird, H., Bakhtin, M., Balteanu, V. A., Barfield, D., Berger, B., Blichfeldt, T., Boink, G., Bugiwati, S. R. A., Cai, Z., Carolan, S., Clark, E., Cubric-Curik, V., Dagong, M. I. A., Dorji, T., Drew, L., Guo, J., Hallsson, J., Horvat, S., Kantanen, J., Kawaguchi, F., Kazymbet, P., Khayatzadeh, N., Kim, N., Shah, M. K., Liao, Y., Martinez, A., Masangkay, J., Masaoka, M., Mazza, Raffaele, Mcewan, J., Milanesi, Marco, Omar, F. M., Nomura, Y., Ouchene-Khelifi, N. -A., Pereira, F., Sahana, G., Salavati, M., Sasazaki, S., Da Silva, A., Simcic, M., Solkner, J., Sutherland, A., Tigchelaar, J., Zhang, H., Ajmone Marsan, Paolo, Bradley, D. G., Colli, Licia, Drogemuller, C., Jiang, Y., Lei, C., Mannen, H., Pompanon, F., Tosser-Klopp, G., Lenstra, J. A., Kijas, J., Guldbrandtsen, B., Denoyelle, L., Sarry, J., le Talouarn, E., Alberti, A., Orvain, C., Engelen, S., Duby, D., Martin, P., Danchin, C., Duclos, D., Allain, D., Arquet, R., Mandonnet, N., Naves, M., Palhiere, I., Rupp, R., Rezaei, H. R., Foran, M., Stella, A., Del Corvo, Marcello, Crisa, A., Marletta, D., Crepaldi, P., Ottino, M., Randi, E., Mujibi, D. F., Gondwe, T., Benjelloun, B., Taela, M. D. G., Nash, O., Moaeen-ud-Din, M., Visser, C., Goyache, F., Alvarez, I., Amills, M., Sanchez, A., Capote, J., Jordana, J., Pons, A., Balears, I., Molina, A., Mruttu, H. A., Masiga, C. W., Van Tassell, C. P., Reecy, J., Luikart, G., Sikosana, J., Anila, H., Petrit, D., Roswitha, B., Philippe, B., Aziz, F., Christos, P., El-Barody, M. A. A., Pierre, T., Phillip, E., Gordon, L., Albano, B. -P., Stephanie, Z., Michel, T., Georg, E., Horst, B., Eveline, I. -A., Luhken, G., Krugmann, D., Eva-Maria, P., Shirin, L., Katja, G., Christina, P., Jutta, R., Marco, B., Andreas, G., Al Tarrayrah, J., Georgios, K., Olga, K., Katerina, K., Christina, L., Anton, I., Lazlo, F., Gabriele, C., Elisabetta, M., Marco, P., Antonello, C., Tiziana, S., Mario, C., Francesca, F., Stefano, G., Marta, M., Bordonaro, S., Giuseppe, D. U., Fabio, P., Mariasilvia, D. A., Alessio, V., Irene, C., Lorraine, P., Mahamoud, A. -S., Van Cann, L. M., Roman, N., Popielarczyk, D., Ewa, S., Augustin, V., Susana, D., Javier, C., Oscar, C., David, G., Regis, C., Gabriela, O. -R., Glowatzki, M. -L., Okan, E., Inci, T., Evren, K., Mike, B., Trinidad, P., Gabriela, J., Godfrey, H., Stella, D., Louise, W., Martin, T., Sam, J., Riccardo, S., Mazza R., Milanesi M., Ajmone-Marsan P. (ORCID:0000-0003-3165-4579), Colli L. (ORCID:0000-0002-7221-2905), Del Corvo M., Nijman, I. J., Rosen, B. D., Bardou, P., Faraut, T., Cumer, T., Daly, K. G., Zheng, Z., Cai, Y., Asadollahpour, H., Kul, B. C., Zhang, W. -Y., Guangxin, E., Ayin, A., Baird, H., Bakhtin, M., Balteanu, V. A., Barfield, D., Berger, B., Blichfeldt, T., Boink, G., Bugiwati, S. R. A., Cai, Z., Carolan, S., Clark, E., Cubric-Curik, V., Dagong, M. I. A., Dorji, T., Drew, L., Guo, J., Hallsson, J., Horvat, S., Kantanen, J., Kawaguchi, F., Kazymbet, P., Khayatzadeh, N., Kim, N., Shah, M. K., Liao, Y., Martinez, A., Masangkay, J., Masaoka, M., Mazza, Raffaele, Mcewan, J., Milanesi, Marco, Omar, F. M., Nomura, Y., Ouchene-Khelifi, N. -A., Pereira, F., Sahana, G., Salavati, M., Sasazaki, S., Da Silva, A., Simcic, M., Solkner, J., Sutherland, A., Tigchelaar, J., Zhang, H., Ajmone Marsan, Paolo, Bradley, D. G., Colli, Licia, Drogemuller, C., Jiang, Y., Lei, C., Mannen, H., Pompanon, F., Tosser-Klopp, G., Lenstra, J. A., Kijas, J., Guldbrandtsen, B., Denoyelle, L., Sarry, J., le Talouarn, E., Alberti, A., Orvain, C., Engelen, S., Duby, D., Martin, P., Danchin, C., Duclos, D., Allain, D., Arquet, R., Mandonnet, N., Naves, M., Palhiere, I., Rupp, R., Rezaei, H. R., Foran, M., Stella, A., Del Corvo, Marcello, Crisa, A., Marletta, D., Crepaldi, P., Ottino, M., Randi, E., Mujibi, D. F., Gondwe, T., Benjelloun, B., Taela, M. D. G., Nash, O., Moaeen-ud-Din, M., Visser, C., Goyache, F., Alvarez, I., Amills, M., Sanchez, A., Capote, J., Jordana, J., Pons, A., Balears, I., Molina, A., Mruttu, H. A., Masiga, C. W., Van Tassell, C. P., Reecy, J., Luikart, G., Sikosana, J., Anila, H., Petrit, D., Roswitha, B., Philippe, B., Aziz, F., Christos, P., El-Barody, M. A. A., Pierre, T., Phillip, E., Gordon, L., Albano, B. -P., Stephanie, Z., Michel, T., Georg, E., Horst, B., Eveline, I. -A., Luhken, G., Krugmann, D., Eva-Maria, P., Shirin, L., Katja, G., Christina, P., Jutta, R., Marco, B., Andreas, G., Al Tarrayrah, J., Georgios, K., Olga, K., Katerina, K., Christina, L., Anton, I., Lazlo, F., Gabriele, C., Elisabetta, M., Marco, P., Antonello, C., Tiziana, S., Mario, C., Francesca, F., Stefano, G., Marta, M., Bordonaro, S., Giuseppe, D. U., Fabio, P., Mariasilvia, D. A., Alessio, V., Irene, C., Lorraine, P., Mahamoud, A. -S., Van Cann, L. M., Roman, N., Popielarczyk, D., Ewa, S., Augustin, V., Susana, D., Javier, C., Oscar, C., David, G., Regis, C., Gabriela, O. -R., Glowatzki, M. -L., Okan, E., Inci, T., Evren, K., Mike, B., Trinidad, P., Gabriela, J., Godfrey, H., Stella, D., Louise, W., Martin, T., Sam, J., Riccardo, S., Mazza R., Milanesi M., Ajmone-Marsan P. (ORCID:0000-0003-3165-4579), Colli L. (ORCID:0000-0002-7221-2905), and Del Corvo M.

Abstract

By their paternal transmission, Y-chromosomal haplotypes are sensitive markers of population history and male-mediated introgression. Previous studies identified biallelic single-nucleotide variants in the SRY, ZFY and DDX3Y genes, which in domestic goats identified four major Y-chromosomal haplotypes, Y1A, Y1B, Y2A and Y2B, with a marked geographical partitioning. Here, we extracted goat Y-chromosomal variants from whole-genome sequences of 386 domestic goats (75 breeds) and seven wild goat species, which were generated by the VarGoats goat genome project. Phylogenetic analyses indicated domestic haplogroups corresponding to Y1B, Y2A and Y2B, respectively, whereas Y1A is split into Y1AA and Y1AB. All five haplogroups were detected in 26 ancient DNA samples from southeast Europe or Asia. Haplotypes from present-day bezoars are not shared with domestic goats and are attached to deep nodes of the trees and networks. Haplogroup distributions for 186 domestic breeds indicate ancient paternal population bottlenecks and expansions during migrations into northern Europe, eastern and southern Asia, and Africa south of the Sahara. In addition, sharing of haplogroups indicates male-mediated introgressions, most notably an early gene flow from Asian goats into Madagascar and the crossbreeding that in the 19th century resulted in the popular Boer and Anglo-Nubian breeds. More recent introgressions are those from European goats into the native Korean goat population and from Boer goat into Uganda, Kenya, Tanzania, Malawi and Zimbabwe. This study illustrates the power of the Y-chromosomal variants for reconstructing the history of domestic species with a wide geographical range.

Published
2022

3. Semi-parametric kernel-based identification of Wiener systems

Author

Risuleo, Riccardo S., Lindsten, Fredrik, Hjalmarsson, Håkan, Risuleo, Riccardo S., Lindsten, Fredrik, and Hjalmarsson, Håkan

Abstract

We present a technique for kernel-based identification of Wiener systems. We model the impulse response of the linear block with a Gaussian process. The static nonlinearity is modeled with a combination of basis functions. The coefficients of the static nonlinearity are estimated, together with the hyperparameters of the covariance function of the Gaussian process model, using an iterative algorithm based on the expectation-maximization method combined with elliptical slice sampling to sample from the posterior distribution of the impulse response given the data. The same sampling method is then used to find the posterior-mean estimate of the impulse response. We test the proposed algorithm on a benchmark of randomly-generated Wiener systems.

Published
2018
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4. Blind system identification using kernel-based methods

Author

Bottegal, Giulio, Risuleo, Riccardo S., Hjalmarsson, Håkan, Bottegal, Giulio, Risuleo, Riccardo S., and Hjalmarsson, Håkan

Abstract

We propose a new method for blind system identification. Resorting to a Gaussian regression framework, we model the impulse response of the unknown linear system as a realization of a Gaussian process. The structure of the covariance matrix (or kernel) of such a process is given by the stable spline kernel, which has been recently introduced for system identification purposes and depends on an unknown hyperparameter. We assume that the input can be linearly described by few parameters. We estimate these parameters, together with the kernel hyperparameter and the noise variance, using an empirical Bayes approach. The related optimization problem is efficiently solved with a novel iterative scheme based on the Expectation-Maximization method. In particular, we show that each iteration consists of a set of simple update rules. We show, through some numerical experiments, very promising performance of the proposed method., Comment: 15 pages; accepted for publication at IFAC Sysid 2015

Published
2014
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