Water-soluble calix[4]resorcarenes as enantioselective NMR shift reagents for aromatic compounds

A tetra L-prolinylmethyl derivative of a tetra-sulfonated calix[4]resorcarene (1) is an effective chiral NMR solvating agent for water-soluble compounds with phenyl, pyridyl, bicyclic aromatic, or indole rings. These aromatic compounds form host-guest complexes with the calix[4]resorcarene in water. Complexation of substrates with the calix[4]resorcarene is likely promoted by hydrophobic effects, and bicyclic substrates have association constants with the calix[4]resorcarene larger than those of similar phenyl-containing compounds. Aromatic resonances of the substrates show substantial upfield shifts because of shielding from the aromatic rings of the calix[4]resorcarene, and several resonances in the 1H NMR spectra typically exhibit enantiomeric discrimination. The extent of enantiomeric discrimination depends in part on interactions of the substituent groups of the substrates with the prolinylmethyl groups of the calix[4]resorcarene. The effectiveness of a calix[4]resorcarene prepared from N-methyl-L-alanine (2) as a chiral NMR discriminating agent is compared to the L-prolinylmethyl derivative.     

Calixarenes and calix[4]resorcinarenes as chiral NMR solvating agents

Calixarenes (CAs) and calix[4]resorcinarenes are cavity compounds, chiral analogues of which have the potential to be used as reagents for the differentiation of enantiomers in NMR spectroscopy. The nature of the substituent groups attached to the cavity permits the preparation of organic- or water-soluble analogues. In NMR applications, chirality of the CAs or calix[4]resorcinarene is usually achieved through the attachment of enantiomerically pure substituent groups. The use of inherently chiral analogues for chiral differentiation is less common. The range of CAs and calix[4]resorcinarenes that have been used for chiral analysis in NMR spectroscopy is reviewed.     

A sulfonated calix[4]resorcinarene with l-pipecolinic acid groups as a water-soluble chiral NMR solvating agent

A water-soluble calix[4]resorcinarene containing l-pipecolinic acid groups is investigated as a chiral NMR solvating agent for aromatic-containing substrates. The substrates form complexes by insertion of the aromatic ring into the cavity of calix[4]resorcinarene. Compounds with phenyl, naphthyl, indole, indoline and pyridyl rings were investigated. The substrates also have ammonium or carboxylate functional groups. The effectiveness of the calix[4]resorcinarene with l-pipecolinic acid groups is compared to similar reagents with proline, hydroxyproline, and α-methylproline moieties that have previously been reported. The derivative with l-pipecolinic acid usually produces better enantiomeric discrimination compared to previous calix[4]resorcinarene reagents.     

A sulfonated calix[4]resorcinarene with α-methyl-l-prolinylmethyl groups as a water-soluble chiral NMR solvating agent

A water-soluble calix[4]resorcinarene containing α-methyl-l-prolinylmethyl groups was investigated as a chiral NMR solvating agent. Substrates form complexes by insertion of the aromatic ring into the cavity of the calix[4]resorcinarene. Amino acid derivatives with phenyl or indole rings, ammonium substrates with pyridyl, indane or dihydroindole rings, and phenyl-containing substrates with carboxylic acid and/or hydroxyl groups were studied. The effectiveness of the α-methyl-l-prolinylmethyl calix[4]resorcinarene is compared to similar reagents with proline and hydroxyproline moieties that have previously been reported. The α-methyl-l-prolinylmethyl derivative causes larger enantiomeric discrimination of one or more ¹H resonances than the previous systems for most of the substrates.     

Structural Characterization of l-proline and Morpholine Appended Chiral Calix[4]resorcinarene Molecules

Calix[4]resorcinarenes serve as host molecules for small guest molecules. Recently calixarenes have been appended to chiral molecules in an attempt to promote chiral recognition. To take advantage of both cavity host and chiral substituent properties the position of the chiral moiety is important. We report the synthesis and structural characterization of two calix[4]resorcinarene based molecules that have helical chirality in the solid state. The calix[4]resorcinarene 1 has chiral l-proline ethyl ester substituents positioned perpendicular to the cavity whereas the calix[4]resorcinarene 2 has morpholines positioned parallel to the cavity which extend the depth of the cavity. Compound 1 is one of the first compounds to show the position of chiral centers with respect to the calixarene cavity. 1H and 13C NMR spectroscopy indicate that the helical chirality of 2 is retained at low temperature in nonpolar solvents.     

An enantioselective NMR shift reagent for cationic aromatics

[structure: see text] The water-soluble tetra l-prolinylmethyl derivative of a tetrasulfonated calix[4]resorcarene is an effective chiral NMR solvating agent for compounds with bicyclic aromatic or indole rings. Complexation of bicyclic substrates with the calix[4]resorcarene is likely promoted by hydrophobic effects. The bicyclic substrates have larger association constants with the calix[4]resorcarene than similar phenyl-containing compounds. Substantial enantiomeric discrimination is observed for several resonances in the (1)H NMR spectra of these substrates.     

Inherently chiral biscalixarene cone–cone conformers consisting of calix[4]arene and calix[5]arene subunits

Inherently chiral biscalixarenes with hetero-cavities were synthesized by a covalent assembly of p-tert-butylcalix[5]arene with a 1,3-substituted calix[4]arene via 1,3-alkylation reaction and subsequent desymmetrization. The racemates were resolved by chiral HPLC method. ¹H NMR spectra, VT-NMR spectra, and theoretical calculations support that the calix[5]arene subunit of the inherently chiral calix[4][5]arene ester adopts a cone-in conformation, with the aromatic ring bearing the CH₂CO₂Et group tilting inward the calix[5]arene cavity. By contrast, such a cone-in structural feature of the calix[5]arene subunit disappears for the corresponding inherently chiral calix[4][5]arene carboxylic acid, due to the intramolecular hydrogen bonding between the carboxyl group and an ethereal oxygen of the glycolic chain.     

无溶剂法合成4,6,10,12,16,18,22,24-八羟基-2,8,14,20-四-{(联三-(3-苯基-2,4,8,10-四氧杂螺[5.5]十一烷基))-(4-(2-(4,6,10,12,16,18,22,24-八羟基)杯芳基)苯基)}杯芳烃螺环树形大分子化合物

以对苯二甲醛、丙二腈为原料, 合成对苯二甲醛单缩醛, 再与季戊四醇反应得到了2,4,8,10-四氧杂-2,9-二(4-二氰基乙烯基苯基)螺[5.5]十一烷, 经水解, 与丙二腈反应, 制备了中间体2,4,8,10-四氧杂-2-(4-二氰基乙烯基苯基)-9-(4-甲酰基苯基)螺[5.5]十一烷(3). 用乙酸酐保护的对苯二甲醛单缩醛与间苯二酚反应, 制备了杯芳烯中间体(6). 将化合物6与过量的化合物3反应, 得到中间体7, 经水解后与过量的化合物6反应, 得到了4,6,10,12,16,18,22,24-八羟基-2,8,14,20-四-{(联三-(3-苯基-2,4,8,10-四氧杂螺[5.5]十一烷基))-(4-(2-(4,6,10,12,16,18,22,24-八羟基)杯芳基)苯基)}杯芳烃螺环树形大分子化合物(9). 总收率为12.7%. 产物结构用IR, 1H NMR, 13C NMR, MS 和元素分析进行了表征, 对影响反应的因素进行了讨论.     

杯[4]间苯二酚芳烃Schiff碱衍生物的合成及其离子萃取性能

通过控制条件,使两种乙氧基羰基甲氧基杯[4]间苯二酚芳烃2a和2b的酯基与1,6-己二胺的一个氨基反应形成酰胺3a和3b,剩余的一个氨基再与水杨醛反应,得到了相应的杯芳烃Schiff碱衍生物4a和4b,对其进行了金属离子的液-液萃取性能研究.结果表明,Schiff碱基团的引入能大大增强杯芳烃与金属离子的配位能力,而杯芳烃空腔的存在又能提高Schiff碱与金属离子的配位选择性.     

无溶剂法合成杯[4]芳烯星形化合物

以对苯二甲醛、乙酸酐为原料合成对苯二甲醛单缩醛, 接着与间苯二酚反应, 制备了含醛基杯[4]芳烯. 利用季戊四醇与含醛基杯[4]芳烯反应, 进而再与3-[4-(2,5-二氧杂环戊基)苯基]-9-[4-二(甲羰氧基)甲基苯基]-2,4,8,10-四氧杂螺环[5.5]十一烷反应, 合成了杯[4]芳烯星形化合物, 收率为65.2%. 产品结构经 IR, ¹H NMR, MS 和元素分析进行了表征.     

Complete 1H and 13C NMR spectral assignment of cis- and trans- 3-(2-[2-(4-methylphenyl)ethenyl]phenyl])sydnones

1H and 13C NMR spectra of cis- and trans-3-(2-[2-(4-methylphenyl)ethenyl]phenyl])sydnones, the first stilbene-substituted mezoionic oxadiazolium rings, were fully assigned combining the information in various solvents, such as deuterated benzene, acetone and chloroform, using 2D NMR techniques.     

Phosphorylation of Dialkylaminomethylated Calix[4]-Resorcinarenes with Some P(III) and P(IV) Derivatives

Abstract

The phosphorylation of dialkylaminomethylated calix[4]resorcinarenes with P(m)-amides and P(TV)chlorides under various conditions results in the formation of different structures with phosphorus containing fragments fixed on the cavity rim. Hydrophosphoryl compounds based on dialkylaminomethylated calix[4]resorcinarenes have been synthesized and some of their properties investigated.     

Synthesis of chiral calix[4]arenes bearing tartaric ester moieties

The synthesis of chiral calix[4]arenes with tartaric acid ester moieties has been achieved by the reactions of tartaric ester chloroacetates with calix[4]arenes in moderate yields. All the chiral calix[4]arene derivatives are in a cone conformation according to the ¹H NMR doublet–doublet pattern of the protons of the methylene groups between the phenol rings. The results of NMR and specific rotations indicate that the molecules have C₂ symmetry with asymmetric features.     

Mechanistic study of enantiomeric recognition with native gamma-cyclodextrin by capillary electrophoresis,reversed-phase liquid chromatography,nuclear magnetic resonance spectroscopy,electrospray mass spectrometry and circular dichroism techniques

The possible mechanisms for the chiral recognition of 2(S)-(3,5-bis-trifluoromethyl-phenyl)-2-[3(S)-(4-fluorophenyl)-4-(1H-[1,2,4]triazol-3-ylmethyl)-morpholin-2(R)-yloxy]-ethanol (compound A) and its enantiomer with native gamma-cyclodextrin (gamma-CD) were investigated using capillary electrophoresis (CE), reversed-phase liquid chromatography (RPLC), proton (1H), fluorine (19F) and carbon (13C) nuclear magnetic resonance spectroscopy (NMR), electrospray mass spectrometry (ESI-MS) and circular dichroism (CD). All experiments provided clear evidence of the formation of diastereomeric complexes between the enantiomers and gamma-CD. Proton, fluorine and carbon NMR spectra suggested that both aromatic rings, with mono-fluoro and bis-tri-fluoro functional groups, on the guest molecule were partially included into the cavity of the gamma-CD. ESI-MS spectra indicated that the diastereomeric complexes have a 1:1 stoichiometric ratio. The binding constants of the diastereomeric complexes obtained by CE, RPLC and CD were compared. The effects of the gamma-CD concentration, organic modifiers and temperature on the CE-chiral separation were also investigated.     

新型间苯二酚杯芳烃硫脲衍生物对阴离子的识别

通过间苯二酚杯芳烃连续三步反应, 以较高产率合成了分子中连有8个和12个硫脲端基的间苯二酚杯芳烃的酰胺衍生物. 用紫外可见光谱法研究了两个代表性化合物4,6,10,12,16,18,22,24-八[6-(苯基硫脲基)-己氨甲酰基甲氧基]-2,8,14,20-四苯基杯[4]间苯二酚芳烃(THBC)和4,6,10,12,16,18,22,24-八[2-(苯基硫脲基)-1-甲基乙基-1-氨甲酰基甲氧基]-2,8,14,20-四苯基杯[4]间苯二酚芳烃(TPBC), 对各种阴离子(AcO^－, H₂PO₄^－, HSO₄^－, H₂PO₄^2－, C₁₂H₂₅-C₆H₄-SO₃^－, Cr₂O₇^2－, B₄O₇^2－, Cl^－, Br^－)的识别性能, 结果表明它们对AcO^－, H₂PO₄^－, HSO₄^－等阴离子有较好的配位作用, 能形成1∶3的配合物.     

A novel synthetic approach to very late antigen-4 antagonist trans-4-[1-[[2,5-dichloro-4-(1-methyl-3-indolylcarboxyamide)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid via tert-butyl trans-[(4S)-Methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylate as a key intermediate

This contribution describes a novel synthetic approach to very late antigen-4 (VLA-4) antagonist trans-4-[1-[[2,5-dichloro-4-(1-methyl-3-indolylcarboxyamide)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid (1) via tert-butyl trans-[(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylate (2b) as a key intermediate. The synthesis, which includes n-Bu?NSO?H that catalyzed basic etherification of 12 and iodine-mediated cyclization to provide the 2,4-disubstituted pyrrolidine frame of 2b, is designed to utilize trans-4-hydroxycyclohexanecarboxylic acid (9) as a commercially available starting material.     

Mechanistic study of the enantiomeric recognition of a basic compound with negatively charged single-isomer gamma-cyclodextrin derivatives using capillary electrophoresis,nuclear magnetic resonance spectroscopy,and infrared spectroscopy

The possible mechanisms for the chiral recognition of 2-(R)-N-[1-(6-aminopyridin-2-ylmethyl)piperidin-4-yl]-2-[(1R)-3,3-difluorocyclopentyl]-2-hydroxy-2-phenylacetamide (RR-M3), and its enantiomer (SS-M3) with octakis(2,3-di-O-acetyl-6-sulfo)-gamma-cyclodextrin (ODAS-gamma-CD) and octakis(6-sulfo)-gamma-cyc?pdextrom enantiomer; (OS-gamma-CD), were investigated using capillary electrophoresis (CE), proton ((1)H), fluorine ((19)F) and carbon ((13)C) nuclear magnetic resonance spectroscopy (NMR), and infrared (IR) spectroscopy. Clear evidence for the formation of diastereomeric complexes between the enantiomers and the two CDs was observed. NMR spectra suggest that the phenyl and difluorocyclopentyl rings are involved in the complexation. The phenyl ring on the guest molecule is deeply penetrated into the cavity of OS-gamma-CD, but it is not included into the cavity of ODAS-gamma-CD. The continuous variation plots built based on the (1)H NMR and IR spectra indicate a 1:1 complex stoichiometric ratio of the M3 enantiomers for both CDs. The affinity of the enantiomers for the two CDs is opposite.     

Optically pure calix[6]tris-ammoniums: syntheses and host-guest properties toward neutral guests

[reaction: see text] Optically pure calix[6]arenes bearing chiral amino arms 4, 7, and 10 have been synthesized in high yields from the known symmetrically 1,3,5-trismethylated calix[6]arene. For both compounds 7 and 10, the key step consists of an efficient selective alkylation on the narrow rim of the calix[6]arene with Ba(OH)2 as the base. All of these chiral calix[6]tris-amines possess a similar flattened cone conformation with the cavity occupied by the methoxy groups. In contrast to 4 and 7, upon protonation, the enantiopure calix[6]arene 10 can switch to the opposite flattened cone conformation through self-assembly of its ammonium arms in an ion-paired cap which closes the cavity. As shown by NMR host-guest studies and an X-ray structure, the obtained polarized host (10 x 3H+) behaves as a remarkable endo-receptor for small polar neutral molecules. Thanks to the tris-cationic chiral binding site of 10 x 3H+, it was shown that the guests experience a chiral environment upon inclusion. Finally, the first example of enantioselective molecular recognition inside the cavity of a calix[6]arene has been evidenced with a racemic 1,2-diol guest.     

基于杯芳烃的分子容器的合成及其对有机铵的可逆识别

将三(吡啶基甲基)胺(TPA)引入杯芳烃的下缘, 合成了一种新的具有杯状结构的杯芳烃衍生物, 研究了其对有机铵的分子识别行为.     

Surface Activities of Calix[4] resorcinarenes Bearing Four Hydrophobic Chains and Its Sol ubilization for Organic Compounds

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