Synthesis of monoalkylated calix[4]arenes via direct alkylation

A new one-step procedure for the synthesis of monoalkylated calix[4]arenes is presented. Reaction of calix[4]arene 1a or 1b with 1.2 equivalent of a weak base (K2CO3 in MeCN or CsF in DMF) and excess of alkylating agent affords the monoalkylated calix[4]arenes in moderate to good yield

Recommendations for the clinical interpretation and reporting of copy number gains using gene panel NGS analysis in routine diagnostics

Next-generation sequencing (NGS) panel analysis on DNA from formalin-fixed paraffin-embedded (FFPE) tissue is increasingly used to also identify actionable copy number gains (gene amplifications) in addition to sequence variants. While guidelines for the reporting of sequence variants are available, guidance with respect to reporting copy number gains from gene-panel NGS data is limited. Here, we report on Dutch consensus recommendations obtained in the context of the national Predictive Analysis for THerapy (PATH) project, which aims to optimize and harmonize routine diagnostics in molecular pathology. We briefly d

Calix[4]arenes, molecular platforms for supramolecular structures

A new strategy for the synthesis of receptor molecules comprises the combination of medium-sized molecules to which functional groups for intermolecular interactions can be attached. Most efforts concern the functionalization of calix[4]arenes, but other building blocks like cyclodextrins and octols are used as well. Selective mono-, 1,2-di, 1,3-di-, and tetraalkylation of calix[4]arenes can be achieved by variation of the alkylation conditions. The calix[4]arenes can be (selectively) functionalized at the “upper rim” by a variety of methods including ipso-nitration. Combination of the calix[4]arenes with crown ethers to calixcrowns gave receptors with a high K+/Na+-selectivity and with terphenyls calixspherands were obtained that form kinetically stable complexes with Na+, K+ and Rb+. Bridging of calix[4]arene with a salophene moiety gave a receptor for urea that can effectively transport urea through a supported liquid membrane. Calix[4]arenes can be combined covalently to double and triple calixarenes and with selectively functionalized octols. When substituted with hydrogen bond donors and acceptors like 2-pyridone, calixarenes undergo self-association to larger aggregrates

Solvent effects on the conformations and hydrogen bond structure of partially methylated p-tert-butylcalix[4]arenes

The effect of the solvent on the conformations of unsubstituted p-tert-butylcalix[4]arene (1) and its methyl ethers 2–6 has been investigated by 1H NMR spectroscopy. The conformational distribution of the 1,2-dimethyl ether 4 and of the tetramethyl ether 6 is strongly influenced by the solvent used. The exact geometry of the cone conformation of the 1,3-dimethyl ether 3 and of the 1,2-dimethyl ether 4 changes from distinct C2 symmetry in CCl4 to close to C4 symmetry in CS2. It seems that inclusion of a small solvent molecule (e.g. CS2) in the cone conformation can take place. Spectra recorded at temperatures up to 125°C in CDCl2CDCl2 showed that the mono- and 1,3-di-methyl ethers are fixed in the cone conformation, whereas the unsubstituted calix[4]arene and the tetramethyl ether are flexible. These observations support a concerted mechanism for the cone-to-cone interconversion in 1, in which two or more phenol rings rotate simultaneously.The hydrogen bonding in partially methylated calix[4]arenes was investigated by IR spectroscopy. In all calix[4]arenes with neighbouring hydroxy groups, a strong cooperativity effect of 80% or more was observed. The exact geometry of the cone conformation affects the strength of the hydrogen bonds, because it influences the O–H O angle in the calix[4]arene. The effect of the solvent on the geometry of the cone conformation is translated in differences of up to 79 cm–1 in the OH-stretch frequencies for spectra recorded in CCl4 and in CS2. \u

Spectroscopic and crystallographic study of 27,28-diethoxy-p-tert-butylcalix[4]arenes

The molecular conformation of the anti form of the title compound, i.e. with the two neighbouring phenylethylether fragments in anti positions, is a partial cone. The conformation is stabilized by two intramolecular hydrogen bonds. These bonds involve both the phenolic OH groups as donors and a hydroxyl group and an ethoxygroup as acceptors. FT-IR solid state spectra reveal two OH bands at 3388 and 3175 cm¿1 which is in accordance with the observed hydrogen-bond configuration. In CCl4 solution the partial cone is preserved for the anti form (3378 and 3187 cm¿1) while the corresponding syn form mainly adopts a cone conformation characterized by O---H stretching vibrations at 3360 and 3168 cm¿1

Synthesis of Monoalkylated Calix[4]arenes via Direct Alkylation

A new one-step procedure for the synthesis of monoalkylated calix[4]arenes is presented. Reaction of calix[4]arene 1a or 1b with 1.2 equivalent of a weak base (K2CO3 in MeCN or CsF in DMF) and excess of alkylating agent affords the monoalkylated calix[4]arenes in moderate to good yields

Upper rim calixcrowns: elucidation of the mechanism of conformational interconversion of calix[4]arenes by quantitative 2-D EXSY NMR spectroscopy

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