Search results for "Rearrangement"
showing 10 items of 298 documents
Regional Susceptibility in VCD Spectra to Dynamic Molecular Motions
2018
Experimental and theoretical studies of the vibrational circular dichroism (VCD) spectrum of 3-methyl-1-(methyldiphenlsilyl)-1-phenylbutan-1-ol, whose absolute configuration is key to elucidating the Brook rearrangement of tertiary benzylic α-hydroxylsilanes, are presented. It is found that the entire OH-bending region in this spectrum—a region that provides important marker bands—cannot be reproduced at all by standard theoretical approaches even though other regions are well described. Using a novel approach to disentangle contributions to the rotational strength of these bands, internal coordinates are identified that critically influence the appearance of this part of the spectrum. We s…
Radical addition to iminium ions and cationic heterocycles
2014
Carbon-centered radicals represent highly useful reactive intermediates in organic synthesis. Their nucleophilic character is reflected by fast additions to electron deficient C=X double bonds as present in iminium ions or cationic heterocycles. This review covers diverse reactions of preformed or in situ-generated cationic substrates with various types of C-radicals, including alkyl, alkoxyalkyl, trifluoromethyl, aryl, acyl, carbamoyl, and alkoxycarbonyl species. Despite its high reactivity, the strong interaction of the radical’s SOMO with the LUMO of the cation frequently results in a high regioselectivity. Intra- and intermolecular processes such as the Minisci reaction, the Porta react…
Experimental and DFT Studies on Competitive Heterocyclic Rearrangements. A Cascade Isoxazole-1,2,4-Oxadiazole-Oxazole Rearrangement
2009
The thermal rearrangements of 3-acylamino-5-methylisoxazoles 1 have been investigated under basic and neutral conditions and interpreted with the support of computational data. The density functional theory (DFT) study on the competitive routes available for the base-catalyzed thermal rearrangement of isoxazoles 1 showed that the Boulton-Katritzky (BK) rearrangement, producing the less stable 3-acetonyl- 1,2,4-oxadiazoles 5, is a much more favored process than either the migration-nucleophilic attack-cyclization (MNAC) or the ring contraction-ring expansion (RCRE). In turn, an increase in reaction temperature will promote the MNAC of oxadiazoles 5, producing the more stable 2-acylaminooxazo…
Meinvalda pārgrupēšanās jonu šķidrumu vidē
2016
Meinvalda pārgrupēšanās jonu šķidrumu vidē. Ikkere L.E., darba vadītājs Dr.h.ķīm., prof. Zicmanis A. Bakalaura darbs, 54 lappuses, 24 attēli, 12 tabulas, 42 literatūras avoti, 5 pielikumi. Latviešu valodā. Bakalaura darba literatūras apskatā ir apkopota galvenā informācija par Meinvalda pārgrupēšanās reakcijām, to katalizatoriem, kā arī par jonu šķidrumiem. Laboratorijā tika veikta trīs jonu šķidrumu sintēze. To struktūras tika pierādītas, izmantojot 1H KMR un IS spektroskopijas metodes. Tika piemeklēti piemērotākie gāzu hromatogrāfijas apstākļi, lai noteiktu pārgrupēšanās reakciju izejvielas un produktus. Tika pārbaudīti dažādu anjonu un slāpekli saturošu katjonu jonu šķidrumu izmantošana …
Fluorinated Heterocyclic Compounds. An Effective Strategy for the Synthesis of Fluorinated Z-Oximes of 3-Perfluoroalkyl-6-phenyl-2H-1,2,4-triazin- 5-…
2005
The reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of the hydrazine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure with enlargement, leads with high yield and in very mild experimental conditions to the formation of Z-oximes of 3-perfluoroalkyl-6-phenyl-2H-1,2,4-triazin-5-ones (11a-c) as major products of the reaction. In turn, the hydrazine can attack the electrophilic carbonyl carbon giving 4-perfluoroacylamino-5-phenyl-2H-1,2,3-triazoles (13a-c) through the well-known Boulton-Katritzky rearrangement of the inter…
Human papillomavirus:Its identikit and controversial role in oral oncogenesis,premalignant an malignant lesions(Review)
2007
Human papillomaviruses (HPVs) are a group of host-specific DNA viruses, with a remarkable epithelial cell specificity: they have been reported principally in the ano-genital tract, urethra, skin, larynx, tracheo-bronchial and oral mucosa. More than 100 different HPV types have been identified and classified as high (e.g. 16, 18, 31) or low (e.g. 11, 42, 36) -risk (HR and LR), based on their association with cervical carcinoma. The carcinogenic role of HR-HPV revolves mainly around two of its oncoproteins: HPV-E6 which promotes degradation of the p53 tumour suppressor gene product and HPV-E7 which modifies the pRb tumour suppressor gene product, inhibiting the activity of TGF-beta2. Since th…
Mapping genomic rearrangements in titi monkeys by chromosome flow sorting and multidirectional in-situ hybridization.
2004
We developed chromosome painting probes for Callicebus pallescens from flow-sorted chromosomes and used multidirectional chromosome painting to investigate the genomic rearrangements in C. cupreus and C. pallescens. Multidirectional painting provides information about chromosomal homologies at the subchromosomal level and rearrangement break points, allowing chromosomes to be used as cladistic markers. Chromosome paints of C. pallescens were hybridized to human metaphases and 43 signals were detected. Then, both human and C. pallescens probes were hybridized to the chromosomes of another titi monkey, C. cupreus. The human chromosome paints detected 45 segments in the haploid karyotype of C.…
Soft tissue Ewing sarcoma--peripheral primitive neuroectodermal tumor with atypical clear cell pattern shows a new type of EWS-FEV fusion transcript.
2000
This study describes a new case of Ewing sarcoma (ES)-peripheral primitive neuroectodermal tumor (pPNET) with unusual phenotype and fusion gene structure. The tumor located in the inguinal area of a 15-year-old boy showed a highly aggressive behavior with hematogenous metastases after intensive chemotherapy and bone marrow transplant, causing death 28 months after diagnosis. The tumor displayed a clear cell pattern, and several neuroectodermal markers proved positive both in the original tumor and in xenografts. This neuroectodermal character was confirmed by electron microscopy. Moreover, cytogenetically the tumor has an unusual chromosomal rearrangement, t(2;22)(q13;q22,t(3;18)(p21;q23); …
Detection of translocations affecting the BCL6 locus in B cell non-Hodgkin's lymphoma by interphase fluorescence in situ hybridization
2001
Structural alterations in 3q27 affecting the BCL6 locus are among the most frequent changes in B-NHL. The aim of the present study was to establish an interphase-FISH assay for the detection of all diverse BCL6 translocations in B-NHL. Two different approaches were tested, one using a PAC-clone spanning the major breakpoint region (MBR) of BCL6 (span-assay), and another using two BAC clones flanking the MBR (flank-assay). Interphase FISH with the span-assay detected the various BCL6 translocations in seven B-NHL cell lines. The dual-color flank-assay was evaluated in two laboratories independently: in normal controls, the cutoff level for false-positive signals was 2.6%, whereas the cutoff …
Chromosome 5 abnormalities in acute lymphoblastic leukemia
1991
Abstract We report two cases of acute lymphoblastic leukemia with involvement of chromosome 5. One of them showed a del(5)(q13q33) in a 5-year-old boy who had previously received antineoplastic chemotherapy for an L1-ALL that had been diagnosed nine months before. The other one showed a t(5;7)(q12–13;q36) together with a t(8;14)(q24;q32) and a der(1) in a 66-year-old man with an L3-ALL. Both chromosome 5 aberrations are interpreted as evolutionary events. In the first case, it was secondary to chemotherapy treatment; in the second, an evolutionary chromosome rearrangement, considering the translocation between chromosomes 8 and 14 as the primary cytogenetic event.