The first synthesis and characterisation of elusive cone 1,2-diformyl tetralkoxycalix[4]arenes and their derivatives (original) (raw)
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Tetrahedron, 1996
a new and general synthetic procedure for the exhaustive and selective introduction of hydroxy groups at the upper rim of calix[4]arenes in the cone conformation is reported. The aldehyde-derivatives of tetraalkoxycalix[4]arenes have been oxidized by Baeyer-Villiger reaction. The introduction of amino and hydroxy groups on calix[4]arene having a rigid cone conformation has been achieved for the first time.A new serie of cone tetraalkoxycalix[4]arenes completely or selectively hydroxylated is reported. In addition, syntheses of rigid cone calix[4]arene-biscrown-3 having amino and hydroxy functions at the upper rim is described.
Functionalization of calix[4]arenes by alkylation with 2-(chloromethyl)pyridine hydrochloride
The Journal of Organic Chemistry, 1992
The syntheses, structures, and conformations of nine of the 13 possible [ (2-pyridylmethyl)oxy]calix[4]arene conformers obtainable by direct substitution on calix[4]arenes la,b are described. The conformer distribution in the exhaustive 0-alkylation of la,b with 2-(chloromethyl)pyridine hydrochloride (PicC1-HC1) in N,N-dimethylformamide (DMF) is strongly affected by the base applied: NaH induces only cone conformers, while KzC03 or CszC03 lead preferentially to partial cone and/or 1,a-alternate conformers, depending on the para substituent of the starting calix[(]arene. Single-crystal X-ray analyses on tetra-0-alkylated cone lk,l and partial cone 2c have been conducted. Molecule lk has a distorted cone conformation with pendant OCH,Py groups; a methanol of solvation is hydrogen bonded to one pyridine N atom and is exo to the calix cavity. The crystal structure of 11 contains two independent distorted cone shaped molecules per asymmetric unit which differ principally in the relative orientations of the OCH,Py groups. In the partial cone conformer 20 the conformation adopted is such that the pendant OCHzPy group of the rotated aryl ring lies in, and effectively fills, the calix cavity produced by the remaining three aryl rings; as in lk a methanol of solvation is hydrogen bonded to a pyridine N atom exo to the calix cavity. Regioselective syn-proximal (l,Z-) or syn-distal(l,3-) difunctionalization at the lower rim of calix[4]arenes has been also achieved. Syn-1,2-disubstituted derivatives have proved to be useful intermediates for the stereoselective synthesis of tTi-O-alkylated cone conformers, &[4]arenea with mixed ligating groups in the sequence AABB at the lower rim, for inherently chiral calix[4]arenes, and for the transfer of proximal regioselectivity from the lower to the upper rim. On the basis of stepwise 0-alkylation of calix[4]arenes, and with the aid of MM2 calculations on the involved intermediates and their anions, a possible genesis of the various conformers is proposed.
Functionalized calix[4]arenes as potential therapeutic agents
Chemical biology & drug design, 2017
Calixarenes, composed of phenolic units linked by methylene bridges at the 2,6-positions, represent a versatile class of macrocyclic compounds in supramolecular chemistry that can host small molecules or ions in their well-defined hydrophobic cavities. In recent years, it has been recognized that this class of compounds has the potential to serve as platform for the design of biological active compounds. Therefore, the calixarenes functionalized with different pharmacophoric groups have been synthesized as target structure by many researchers and were further evaluated for their biological activities. Owing to their promising biological activities such as antiviral, antibacterial, antifungal, and anticancer, the functionalized calixarenes are recently receiving increased attention from pharmaceutical/medicinal chemistry community. In this review, we summarize and discuss the synthetic approaches and the biological potential of functionalized calixarenes, mainly focusing on the selec...
Synthesis of mono- and diboronic acid calix[4]arene receptors
Arkivoc, 2003
Various boronic acid appended calixarene assemblies were constructed on the macrocyclic lower rim. Treatment of the appropriate calix[4]arene with controlled amounts of base and 2bromomethylphenylethylene boronate affords the monoboronic acid triphenol or the distally separated diboronic acid of choice. Upper rim p-allyl calix[4]arene phenyl boronic acids were prepared. These ligands were designed to allow further study of guest complexation in nonaqueous, aqueous and on solid substrates.
An easy access to tetra-o-alkylated calix[4]arenes of cone conformation
Tetrahedron, 1995
Fully 0-alkylated calix[4larenes have been synthesbed by the alkylation of p-tertbutylcalix(4)arene and Its IJdialkylated derivatives in liquid-liquid phase-transfer catalytic process. 1Hd and lH2R2 could effeciently be deprotonated by aqueous NaOH (50% w/w)-toluene system and alkylated with alkyl (aralkyl, allyl) halogens in good yields affording cahx[4]arene tetraethers of cone conformation.
Synthesis of carbohydrate functionalised n-propoxy-Calix[4]arenes
Tetrahedron Letters, 1998
The Suzuki ~action has been used to couple para-bromophenyl glycosides to boronic acid derivatives ofn-propox3,-Calix[41arenc ; " a one-pot " methodology eliminates the need to isolate the boronic acids and increases the overall yield. The synthesis provides a new class of carbohydrate containing calixarencs with a deepened cavi .ly. In order to enlarge the cavity of calix[4]arene derivatives, Atwood et allhave prepared a pphenylcalix[4]arene tetramethylether. Such calix[4]arene derivative should be capable of binding organic guest molecules. However the methyl derivatives are present in the semi-cone conformation, which is neither optimised for guest binding nor for increasing carbohydrate recognition by cooperative interaction. 2 In view of this, the tetra-propyl derivatives blocked in the cone conformation are of great interest. Bearing in mind the significant role played by sugars in many biological events, the coupling of carbohydrate antennae to the calix[4]arenes may provide a new class of molecular vectors. To this end, Dondoni and Ungaro3'4et al have described the synthesis of calix[4]arenes substituted by carbohydrate units at
Journal of Organic Chemistry, 1994
The monospirodienone derivative of 5,11,17,23-tetra-tert-butyl-25,26,27,2~tetr~y~o~~[4]arene (2) undergoes in the presence of an ammonium tribromide salt a spiroannulation reaction at the a-position to the carbonyl. Reaction of 2 with an equimolar amount of LDA followed by treatment with a phosphorylating agent yielded a monosubstituted spirodienone. Reductive cleavage of the latter (K/NH3) afforded 5,11,17,23-tetra-tert-butyl-25,26,27-tr~hy~oxyc~x~ene (10). The structure of 10 was corroborated indirectly by X-ray crystallography of ita bromo dispiro derivative 11. It is concluded that the compound obtained by cleavage of the bis(diethy1 phosphate) ester derivative 13, and previously described by us as 10, is 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26monoaminocalix[4larene (12). The latter readily forms a tosylate salt in CDCl3 solution. Considering this reassignment, the inversion barriers of several OH-depleted aminocalixarenes and their salta are reexamined.