Easily Prepared Chiral Scorpionates: Tris(2-oxazolinyl)boratoiridium(I) Compounds and Their Interactions with MeOTf

Optically active C3-symmetric monoanionic ligands are uncommon in organometallic chemistry. Here we describe the synthesis of readily prepared tris(4S-isopropyl-2-oxazolinyl)phenylborate [ToP] and fluxional, zwitterionic four- and five-coordinate iridium(I) compounds [Ir(ToP)(η4-C8H12)] (4) and [Ir(ToP)(CO)2] (5). The highly fluxional nature of 4 and5 makes structural assignment difficult, and the interaction between the iridium(I) center and the [ToP] ligand is established by solid-state and solution 15N NMR methods that permit the direct comparison between solution and solid-state structures. Although iridium cyclooctadiene 4 is a mixture of four- and five-coordinate species, the dicarbonyl 5 is only the five-coordinate isomer. The addition of electrophiles MeOTf and MeI provides the oxazoline N-methylated product rather than the iridium methyl oxidative addition product. N-Methylation was unequivocally proven by through-bond coupling observed in 1H−15N HMBC experiments

Epidermal differentiation complex (locus 1q21) gene expression in head and neck cancer and normal mucosa

Epidermal differentiation complex (EDC) comprises a number of genes associated with human skin diseases including psoriasis, atopic dermatitis and hyperkeratosis. These genes have also been linked to numerous cancers, among them skin, gastric, colorectal, lung, ovarian and renal carcinomas. The involvement of EDC components encoding S100 proteins, small proline-rich proteins (SPRRs) and other genes in the tumorigenesis of head and neck squamous cell cancer (HNSCC) has been previously suggested. The aim of the study was to systematically analyze the expression of EDC components on the transcript level in HNSCC. Tissue specimens from 93 patients with HNC of oral cavity and 87 samples from adjacent or distant grossly normal oral mucosawere analyzed. 48 samples (24 tumor and 24 corresponding surrounding tissue) were hybridized to Affymetrix GeneChip Human 1.0 ST Arrays. For validation by quantitative real-time PCR (QPCR) the total RNA from all 180 samples collected in the study was analyzed with Real-Time PCR system and fluorescent amplicon specific-probes. Additional set of samples from 14 patients with laryngeal carcinoma previously obtained by HG-U133 Plus 2.0 microarray was also included in the analyses. The expression of analyzed EDC genes was heterogeneous. Two transcripts (S100A1 and S100A4) were significantly down-regulated in oral cancer when compared to normal mucosa (0.69 and 0.36-fold change, respectively), showing an opposite pattern of expression to the remaining S100 genes. Significant up-regulation in tumors was found for S100A11, S100A7, LCE3D, S100A3 and S100A2 genes. The increased expression of S100A7 was subsequently validated by QPCR, confirming significant differences. The remaining EDC genes, including all encoding SPRR molecules, did not show any differences between oral cancer and normal mucosa. The observed differences were also assessed in the independent set of laryngeal cancer samples, confirming the role of S100A3 and LCE3D transcripts in HNC. In HNC of oral cavity only one family of EDC genes (S100 proteins) showed significant cancer-related differences. A number of other transcripts which showed altered expression in HNC require further validation.

HMQC and refocused-INEPT experiments involving half-integer quadrupolar nuclei in solids

International audienceHetero-nuclear coherence transfers in HMQC and refocused-INEPT experiments involving half-integer quadrupolar nuclei in solids are analyzed. 1D and 2D schemes are considered under MAS for the general case of multi-spin systems SIn (n ≤ 4), where S is an observed nucleus. These results are also discussed in the context of high-resolution schemes featuring MQMAS or STMAS. The theoretical predictions are verified experimentally in a series of 1D and 2D experiments performed at 9.4 and 18.8 T

Easily Prepared Chiral Scorpionates: Tris(2-oxazolinyl)boratoiridium(I) Compounds and Their Interactions with MeOTf

Optically active C3-symmetric monoanionic ligands are uncommon in organometallic chemistry. Here we describe the synthesis of readily prepared tris(4S-isopropyl-2-oxazolinyl)phenylborate [ToP] and fluxional, zwitterionic four- and five-coordinate iridium(I) compounds [Ir(ToP)(η4-C8H12)] (4) and [Ir(ToP)(CO)2] (5). The highly fluxional nature of 4 and5 makes structural assignment difficult, and the interaction between the iridium(I) center and the [ToP] ligand is established by solid-state and solution 15N NMR methods that permit the direct comparison between solution and solid-state structures. Although iridium cyclooctadiene 4 is a mixture of four- and five-coordinate species, the dicarbonyl 5 is only the five-coordinate isomer. The addition of electrophiles MeOTf and MeI provides the oxazoline N-methylated product rather than the iridium methyl oxidative addition product. N-Methylation was unequivocally proven by through-bond coupling observed in 1H−15N HMBC experiments.Reprinted (adapted) with permission from Inorganic Chemistry 47 (2008): 10208, doi:10.1021/ic801637s. Copyright 2008 American Chemical Society.</p

Selective and Efficient Silylation of Mesoporous Silica: A Quantitative Assessment of Synthetic Strategies by Solid-State NMR

Surface silanol groups in mesoporous silica MCM-41 particles were successfully silylated with trimethylsilyl trifluoromethanesulfonate (TMSOTf). Characterization of modified mesoporous silica materials was conducted using X-ray diffraction, infrared spectroscopy, nitrogen absorption, elemental analysis, and solid-state NMR spectroscopy. In particular, extensive use of ¹H, ¹³C, and ²⁹Si solid-state NMR provided unique insights into the silylation process and served as a key guiding tool for the synthetic effort. Treatment of as-synthesized MCM-41 with TMSOTf was found to selectively and efficiently passivate the external surface of particles without assistance of a base, whereas modification by other silylating reagents, including trimethylchlorosilane (TMCS), <i>N</i>,<i>O</i>-bis­(trimethylsilyl)­acetamide (BSA), and triethoxymethylsilane (MeSi­(OEt)₃), yielded lower coverage and/or resulted in partial silylation of the internal surface. The ²⁹Si and ¹H solid-state NMR spectra gave accurate concentrations of silicon sites and densities of trimethylsilyl (TMS) groups on the external and internal surfaces of MCM-41. The ¹H and ¹³C NMR spectra revealed the definite structures and concentrations of all organic species present in the silylated samples. These data highlighted the importance of choosing a proper concentration of the silylating reagent and finding the washing and extraction conditions that result in efficient sequestration of the structure directing agent (surfactant) without detachment of grafted species or production of unwanted surface alkoxy groups