Hypbrvalent Iodine Oxidation of 3-(2-Furyl)-1-(2-hydroxyaryl)prop-2-enones : Synthesis of Novel 2-(2-Furyl)-cis-3-hydroxvchromanones and Derived 3-Hydroxychromones

The synthesis of novel 2-(2-furyl)-cis-3-hydroxychro-manones(3a-c) has been achieved from 3-(2-furyl)-1-(2-hydroxy-aryl)-2-enones (1a-c) via acid catalyzed hydrolysis of dimethylacetals (2a-c), formed by hypervalent iodine oxidation using iodobenzene diacetate in methanolic potassium hydroxide. Action of dil. alkali on 3a and 3b provides a new synthesis of 2-(2-furyl)-3-hydroxychromones (6a, 6b).     

"Spontaneous" ambient temperature dehydrocoupling of aromatic amine-boranes

The dehydrocoupling/dehydrogenation behavior of primary arylamine-borane adducts ArNH(2)?BH(3) (3?a-c; Ar = a: Ph, b: p-MeOC(6)H(4), c: p-CF(3)C(6)H(4)) has been studied in detail both in solution at ambient temperature as well as in the solid state at ambient or elevated temperatures. The presence of a metal catalyst was found to be unnecessary for the release of H(2). From reactions of 3?a,b in concentrated solutions in THF at 22?°C over 24?h cyclotriborazanes (ArNH-BH(2))(3) (7?a,b) were isolated as THF adducts, 7?a,b?THF, or solvent-free 7?a, which could not be obtained via heating of 3?a-c in the melt. The μ-(anilino)diborane [H(2)B(μ-PhNH)(μ-H)BH(2)] (4?a) was observed in the reaction of 3?a with BH(3)?THF and was characterized in situ. The reaction of 3?a with PhNH(2) (2?a) was found to provide a new, convenient method for the preparation of dianilinoborane (PhNH)(2)BH (5?a), which has potential generality. This observation, together with further studies of reactions of 4?a, 5?a, and 7?a,b, provided insight into the mechanism of the catalyst-free ambient temperature dehydrocoupling of 3?a-c in solution. For example, the reaction of 4?a with 5?a yields 6?a and 7?a. It was found that borazines (ArN-BH)(3) (6?a-c) are not simply formed via dehydrogenation of cyclotriborazanes 7?a-c in solution. The transformation of 7?a to 6?a is slowly induced by 5?a and proceeds via regeneration of 3?a. The adducts 3?a-c also underwent rapid dehydrocoupling in the solid state at elevated temperatures and even very slowly at ambient temperature. From aniline-borane derivative 3?c, the linear iminoborane oligomer (p-CF(3)C(6)H(4))N[BH-NH(p-CF(3)C(6)H(4))](2) (11) was obtained. The single-crystal X-ray structures of 3?a-c, 5?a, 7?a, 7?b?THF, and 11 are discussed.     

Reactivity of the A-CH=N-NR-CX-B system. 4-Methyl-5-hydroxy-5-phenyl-(or thienyl)-2,3,4,5-tetrahydro-1,2,4-triazin-3-ones and their ring contraction products

The behaviour of some monosemicarbazones of phenyl- ( 1a-c ) and thienyl-glyoxal ( 2a-c ) towards cyclizing agents has been investigated. Upon aqueous sodium hydroxide treatment, 4-melhyl-semicarbazones 1a and 2a gave the addition products 3 and 4 , respectively, whereas the 2-methyl- and 2,4-dimethyl derivatives 1b,c and 2b,c gave demolition products only. On the other hand, compounds 1b,c gave the addition product 8 and the triazine 7 , respectively, on treatment with aqueous hydrochloric acid. Bromination of 1a,b gave the bromosemicarbazone 10a and a mixture of 10b and 9 , respectively. Performing the same reaction on 3 and 4 at 115°, the 1,3,4-oxadiazoles 13 and 14 have been obtained. The behaviour of bromosemicarbazones [ 10a,b ] and of the bromo-tetrahydrotriazine 9 towards heating or treatment with base has also been investigated.     

Synthesis and conformational studies on hexa-O-alkyl p-unsubstituted calix[6]arenes

[structure: see text] In this article we describe the selective O-benzylation of para-unsubstituted calix[6]arene 1 in rings 1 and 4 (2a-c) and the subsequent alkylation of phenol groups with alpha-haloesters (methyl esters 3a, 3c, and 3e; tert-butyl esters 3b, 3d, and 3f) to determine the effect of these groups on their conformational behavior. 2D NMR studies at 188 K reveal that compounds 2a-c, 3b, 3d, and 3f are less flexible, showing a 1,2,3-alternate conformation. The same conformation has been observed in the solid state.     

Heavy alkaline earth metal pyrazolates: synthetic pathways, structural trends, and comparison with divalent lanthanoids

Two series of heavy alkaline earth metal pyrazolates, [M(Ph(2)pz)(2)(thf)(4)] 1 a-c (Ph(2)pz=3,5-diphenylpyrazolate, M=Ca, Sr, Ba; THF=tetrahydrofuran) and [M(Ph(2)pz)(2)(dme)(n)] (M=Ca, 2 a, Sr, 2 b, n=2; M=Ba, 2 c, n=3; DME=1,2-dimethoxyethane) have been prepared by redox transmetallation/ligand exchange utilizing Hg(C(6)F(5))(2). Compounds 1 a and 2 b were also obtained by redox transmetallation with Tl(Ph(2)pz). Alternatively, direct reaction of the alkaline earth metals with 3,5-diphenylpyrazole at elevated temperatures under solventless conditions yielded compounds 1 a-c and 2 a-c upon extraction with THF or DME. By contrast, [M(Me(2)pz)(2)(Me(2)pzH)(4)] 3 a-c (M=Ca, Sr, Ba; Me(2)pzH=3,5-dimethylpyrazole) were prepared by protolysis of [M[N(SiMe(3))(2)](2)(thf)(2)] (M=Ca, Sr, Ba) with Me(2)pzH in THF and by direct metallation with Me(2)pzH in liquid NH(3)/THF. Compounds 1 a-c and 2 a-c display eta(2)-bonded pyrazolate ligands, while 3 a,b exhibit eta(1)-coordination. Complexes 1 a-c have transoid Ph(2)pz ligands and an overall coordination number of eight with a switch from mutually coplanar Ph(2)pz ligands in 1 a,b to perpendicular in 1 c. In eight coordinate 2 a,b the pyrazolate ligands are cisoid, whilst 2 c has an additional DME ligand and a metal coordination number of ten. By contrast, 3 a,b have octahedral geometry with four eta(1)-Me(2)pzH donors, which are hydrogen-bonded to the uncoordinated nitrogen atoms of the two trans Me(2)pz ligands. The application of synthetic routes initially developed for the preparation of lanthanoid pyrazolates provides detailed insight into the similarities and differences between the two groups of metals and structures of their complexes.     

Ferrocene-modified purines as potential electrochemical markers: synthesis, crystal structures, electrochemistry and cytostatic activity of (ferrocenylethynyl)- and (ferrocenylethyl)purines

Palladium-catalyzed Sonogashira cross-coupling reactions of halopurines 9-benzyl-6-chloropurine (2 a), 9-benzyl-8-bromoadenine (2 b), and 9-benzyl-2-chloroadenine (2 c) with ethynylferrocene (1) gave the corresponding (ferrocenylethynyl)purines 3 a-c in moderate to good yields. Catalytic hydrogenation of these alkynes over Pd/C afforded the respective saturated [2-(ferrocenyl)ethyl]purines 4 a-c. The crystal structures 3 a, 3 b, 4 a and 4 b as determined by X-ray diffraction show interesting solid-state interactions, markedly different for purines 3 a and 4 a on one hand and adenines 3 b and 4 b that possess a free amino group on the other. Electrochemistry of electrochemically labelled purines 3 and 4 has been studied by voltammetry and cyclic voltammetry on platinum disc electrode and the experimental oxidation potentials were confirmed and explained by ionization potentials from theoretical DFT calculations. Several compounds of this series exhibited a considerable cytostatic effect.     

Direct introduction of heterocyclic residues into 1,2,4-triazin-5(2H)ones

3-Aryl-1,2,4-triazin-5(2H)-ones 1a-c react with indoles 2a-c in trifluoroacetic acid/chloroform or in boiling butanol or acetic acid to give 3-aryl-6-(indolyl-3)-1,6-dihydro-1,2,4-triazin-5(2H)-ones 3a-g . Oxidation of the dihydro-1,2,4-triazin-5(2H)-ones 3a-e afforded 6-(indolyl-3)-1,2,4-triazin-5(2H)-ones 4a-e , products of nucleophilic substitution of hydrogen in 1a-c . Refluxing 1b with N-methylpyrrote 5b in butanol for an extended time resulted in the formation of 3-(4-chlorophenyl)-6-(1-meuiylpyrrolyl-2)-1,2,4-triazin-5(2H)-one 4h. The reaction of 1a-c with indoles 2a-c , pyrroles 5a,b , 1,3-dimethyl-2-phenylpyrazol-4-one (8) and aminothiazoles 9a,b in acetic anhydride affords the 1-acetyl-3-aryl-6-hetaryl-1,6-dihydro-1,2,4-triazin-5(2H)-ones 6a-s . Reaction of 1a-c with N-methyl-pyrrole 5b in acetic anhydride gives beside the 1:1 addition products 6h-k also the 2:1 addition products 7a-c .     

REACTIONS WITH 2-THIOHYDANTOIN DERIVATIVES: SYNTHESIS OF MANNICH BASES AND IMIDAZOTHIAZOLE DERIVATIVES

Abstract

5-Arylidene-2-thiohydantoins (la-c) and 5-arylazo-1-phenyl-2-thiohydantoins (7a, b) were condensed with formaldehyde and primary or secondary aromatic amines to give the corresponding Mannich bases (2a-f) and (8a, b) respectively, which could also be converted into the educts (la-c) and (7a, b) by boiling in ethanolic HCI. On treatment of (2a-f), (5a-c) and (8a, b) with an ethereal diazomethane the colourless cyclopropane products (3a-c) and yellow N-methyl substituted compounds (9, b) were isolated respectively. Alkylation of (2d-f) with methyl iodide and (la-e) with 3-chloropentane-2,4 dione gave the corresponding 2-alkylmercapto derivatives (5a-c) and (2a-c) respectively, the former of which on hydrolysis by boiling ethanolic HCI afforded the hydantoin derivatives (6a-c). Cyclization of (12a-c) using polyphosphoric acid resulted in the formation of imidazothiazole derivatives (13a-c). The structure of the isolated products were established by elemental analyses and spectral data studies.     

A novel reaction of (2a7-trinito-9H-fluoren-9-ylidene)-propanedinitrile with N-arylisoindolines

N-Arylisoindolines 1a-c reacted with (2,4, 7-trinitro-9H-fluoren-9-ylidene)propanedinitrile ( A ) in pyridine with admission of air via a net α-H-atom abstraction and formation of [3-(2-aryl-3-arylimino-2,3-dihydro- 1H-isoindol-1-ylidene)-2-aryl-2,3-dihydro-1H-isoindol-1-ylidene]propanedinitriles 2a-c , N-[2-aryl-3-(2-aryl-3-arylimino-2,3-dihydro-1H-isoindolyl-1-idene)-2,3-dihydro-1H-isoindol-1-ylidene]arenamines 3a, b , N, N'-[2-aryl-1H-isoindole-1,3(2H)-diylidene]bisarenamines 4a, b and N-arylphthalimides 5a-c in moderate yields. 2,4,7-Trinitro-9-fluorenone as well as one reduction product each of the latter and of A, namely compounds 6 and 7 , respectively, are also found. The structure of 2b has been unambiguously confirmed by an X-ray crystal structure analysis. A rationale for the conversions observed is presented. These involve dehydrogenation and oxidative couplings of 1a-c as well as transfer of N-aryl fragment from 1a-c to intermediate products.     

General synthetic entry to linearly-fused dihydrobenzocyclobutene-1,2-diones and benzocyclobutene-1,2-diones via annulation of 1,2-bis(methylene)carbocycles with 3-chloro-3-cyclobutene-1,2-dione

The tandem Diels-Alder/dehydrochlorination reaction of semisquaric chloride (1) with the 1,2-bis(methylene)cycloalkanes 2a-c and 1,2-bis(methylene)-4-cyclohexene (9) affords the linearly-fused cycloalkanodihydrobenzocyclobutene-1,2-diones 3a-c and 3,4,7,8-tetrahydrocyclobuta[b]-naphthalene-1,2-dione (10), respectively. On treatment with MnO2, 3a-c are dehydrogenated to the respective carbocycle-fused benzocyclobutene-1,2-diones 4a-c in good yields. 3a and 3b react with bromine to give the addition products 5a,b, which, on treatment with silver trifluoroacetate, afford the benzocyclobutene-1,2-diones 4a,b. For preparative purposes, the sequence 3-->5-->4 can be performed advantageously as a "one-pot procedure". Double-condensation reactions of 4a,b with alpha,alpha'-biscyano-o-xylene and o-phenylenediamine afford the pentacyclic biphenylenes 7a,b and the cyclobutahetarenes 8a,b, respectively. These cyclobutenediones suggest themselves as building blocks for the construction of extended linearly-fused polycyclic compounds with novel ring sequences. o-Quinodimethanes 12a-g generated in situ by the thermal decomposition of the respective 1,4-dihydro-2,3-benzoxathiin-3-oxides (sultines) 11a-g react with semisquaric chloride (1) to afford the 3,8-dihydronaphtho[b]cyclobutene-1,2-diones 13a-g. These, on dehydrogenation with bromine and/or MnO2, furnish the naphtho[b]cyclobutene-1,2-diones 14a-g in fair to good yields. As described for 4a,b the naphtho[b]cyclobutene-1,2-diones 14a-c are condensed with alpha,alpha'-biscyano-o-xylene and o-phenylenediamine to furnish the pentacyclic biphenylenes 15a-c and the pentacyclic cyclobutahetarenes 16a-c.     

The photochemistry of benzotriazole derivatives. Part 2: photolysis of 1-substituted benzotriazole arylhydrazones: new route to phenanthridin-6-yl-2-phenyldiazines

Irradiation of 1-substituted benzotriazole arylhydrazones 3a-c, 4a,b and 5a,b with a 16 W low pressure mercury arc-lamp (254 nm) for 24 h gave phenanthridin-6-yl-2-phenyldiazines 9a-c, phenanthridin-6(5H)-ones 10a-c, 1-anilinobenzimidazoles 11a-c, 2-aryl-1H-benzimidazoles 12a-c, 1-arylamino-1H-benzimidazol-2-carboxylic acid ethyl esters 14a,b, 1-aryl-1H, 9H-benzo [4,5][1,2,3] triazolo[1,2-a]tetrazole-3-carboxylic acid ethyl esters 16a,b, 1-arylamino-2-benzoylbenzimidazoles 18a,b and 2-benzoylbenzoxazole 21.     

Bridged tetraquaternary salts from N,N'-polyfluoroalkyl-4,4'-bipyridine

4,4'-Bipyridine (1) with excess of polyfluoroalkyl bromide or iodides 2a-d at 100-110 degrees C without solvent gave the monoquaternary salts 3a-d in >90% yields. However, 1 with 2.5 equiv of 2a-c in DMF at 110 degrees C resulted in the diquaternary salts 5a-c in >85% yields. In DMF, 5a-c were obtained in comparable yields when a molar excess of 2a-c reacted with 3a-c. 1,4-Dibromobutane with 3a,b in DMF at 100 degrees C led to the tetraquaternary salts 7a,b in approximately 85% yields. In water or acetone/water as a solvent, salts 3a-d and 5a-c were metathesized with LiN(SO(2)CF(3))(2) and KSO(3)CF(3) to produce monoquaternary ionic liquids 4a-h in >88% yields and diquaternary ionic liquids 6a-f in >86% yields, respectively. Tetraquaternary ionic liquids 8a,b were obtained when LiN(SO(2)CF(3))(2) was reacted with salts 7a,b. These compounds were stable to 340 degrees C as determined by DSC. They are the first N-mono-, N,N'-di-, and N,N,N',N'-tetra-4,4'-polyfluoroalkylbipyridinium quaternary salts and ionic liquids.     

Osmium phosphiniminato complexes: synthesis,protonation, structure,and redox-coupled hydrolytic scission of N-p bonds

The osmium(VI) nitrido complex TpOs(N)Cl(2) [1, Tp = hydrotris(1-pyrazolyl)borate] reacts with triarylphosphines to afford the Os(IV) phosphiniminato complexes TpOs(NPAr(3))Cl(2) [Ar = p-tolyl (tol) (2a), phenyl (2b), p-CF(3)C(6)H(4) (2c)] in nearly quantitative yield. Protonation of 2a-c with 1 equiv of HOTf in MeCN occurs at the phosphiniminato nitrogen to give [TpOs(IV)(NHPAr(3))Cl(2)]OTf (3a-c) in 68-80% yield. Solutions of 2a-c in CH(2)Cl(2) react with excess H(2)O over 1 week to form the disproportionation products 1 (28%), TpOs(III)(NHPAr(3))Cl(2) (4a-c) (60%), and OPAr(3) (35%). Treatment of solutions of 3a-c with H(2)O also affords 1, 4a-c, and OPAr(3). X-ray structures of 2b, 3b, and 4b are presented. Cyclic voltammograms of compounds 2a-c exhibit Os(V)/Os(IV) and Os(IV)/Os(III) couples at approximately 0.3 and -1 V versus Cp(2)Fe(+/0). Protonation to give 3 makes reduction easier by approximately 1.2 V, so that these compounds show Os(IV)/Os(III) and Os(III)/Os(II) couples. In the hydrolytic disproportionation of 2a-c, labeling studies using (18)O-enriched O(2) and H(2)O establish water as the source of the oxygen atom in the OPAr(3) product. The conversions are accelerated by HOTf and inhibited by NaOD. The relative rates of hydrolytic disproportionation of 2a-c vary in the order tol > Ph > p-CF(3)C(6)H(4). The data indicate that protonation of the phosphiniminato nitrogen is required for hydrolysis. The mechanism of the hydrolytic disproportionation is compared to that of the related reaction of the osmium(IV) acetonitrile complex [TpOs(NCMe)Cl(2)](+).     

Synthesis, structural features, absorption spectra, redox behaviour and luminescence properties of ruthenium(ii) rack-type dinuclear complexes with ditopic, hydrazone-based ligands

The isomeric bis(tridentate) hydrazone ligand strands 1 a-c react with [Ru(terpy)Cl3] (terpy=2,2':6',2'-terpyridine) to give dinuclear rack-type compounds 2 a-c, which were characterised by several techniques, including X-ray crystallography and NMR methods. The absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in rigid matrix at 77 K) of the ligand strands 1 a-c and of the metal complexes 2 a-c have been studied. Compounds 1 a-c exhibit absorption spectra dominated by intense pi-pi* bands, which, in the case of 1 b and 1 c, extend within the visible region, while the absorption spectra of the rack-type complexes 2 a-c show intense bands both the in the UV region, due to spin-allowed ligand-centred (LC) transitions, and in the visible, due to spin-allowed metal-to-ligand charge-transfer (MLCT) transitions. The energy position of these bands strongly depends on the ligand strand: in the case of 2 a, the lowest energy MLCT band is around 470 nm, while in 2 b and 2 c, it lies beyond 600 nm. Ligands 1 a-c undergo oxidation processes that involve orbitals based mainly on the CH3--N--N== fragments. The complexes 2 a-c undergo reversible metal-centred oxidation, while reductions involve the hydrazone-based ligands: in 2 b and 2 c, the bridging ligand is reduced twice and in 2 a once before reduction of the peripheral terpy ligands takes place. Ligands 1 a-c exhibit luminescence from the lowest-lying 1pi-pi* level. Only for complex 2 a does emission occur; this may be attributed to a 3MLCT state involving the bridging ligand. Taken together, the results clearly indicate that the structural variations introduced translate into interesting differences in the spectroscopic, luminescence and redox properties of the ligand strands as well as of the rack-type metal complexes.     

Synthesis and anticancer activity of some novel tetralin-6-yl-pyrazoline, 2-thioxopyrimidine, 2-oxopyridine, 2-thioxo-pyridine and 2-iminopyridine derivatives

The title compounds were prepared by reaction of 6-acetyltetralin (1) with different aromatic aldehydes 2a-c, namely 2,6-dichlorobenzaldehyde, 2,6-diflouro-benzaldehyde, and 3-ethoxy-4-hydroxybenzaldehyde, to yield the corresponding a,b-unsaturated ketones 3a-c. Compound 3b was reacted with hydrazine hydrate to yield the corresponding 2-pyrazoline 4, while compounds 3a,b reacted with thiourea to afford the 2-thioxopyrimidine derivatives 5a,b, respectively. The reaction of 1, and the aromatic aldehydes 2a-c with ethyl cyanoacetate, 2-cyano-thioacetamide or malononitrile in the presence of ammonium acetate yielded the corresponding 2-oxopyridines 6a,b, 2-thioxopyridines 7a-c or 2-iminopyridines 8a,b, respectively. The newly prepared compounds were evaluated for anticancer activity against two human tumor cell lines. Compound 3a showed the highest potency with IC(50) = 3.5 and 4.5 μg/mL against a cervix carcinoma cell line (Hela) and breast carcinoma cell line (MCF7), respectively.     

A Convenient Preparation of 2-(2-Arylidene)- and 2-(2-Polyhydroxyalkylidene)hydrazono-4-imidazolidinones with Various Heterocyclic Side Chain Substituents at Position 5 as Potential Antiviral and Antitumor Agents

A variety of novel 5-[( Z )-arylidene]-2-[(2-( E )-arylidene)hydrazono]-4-imidazolidinones 1a-c to 4a , b and 5-[( Z )-arylidene]-2-[(2-( E )-polyhydroxyalkylidene)hydrazono]-4-imidazolidinones 5a-c to 7a-c were prepared from the reaction of 5-[( Z )-arylidene]-2-methylmercaptohydantoins 8a-c with 2-( E )-arylidene hydrazones 13a-d and/or 2-( E )-monosaccharides hydrazones 16a-c . The linear structure, and not that of the angular isomer, has been selected for the products. This structure has been confirmed from a model study of the condensation of 5-[( Z )-2-thienylidene]-2-hydrazono-4-imidazolidinone 9a with benzaldehyde and D -galactose, respectively. The acetylation and benzoylation reactions of compounds 1-7 have been studied. All the new compounds were tested for their potential antiviral and antitumor activities.     

A novel synthesis of precocenes. Efficient synthesis and regioselective O-alkylation of dihydroxy-2,2-dimethyl-4-chromanones

The reactions of trihydroxybenzenes 1a-c and 3-methylbut-2-enoic acid ( 2 ) in a zinc chloride/water/phosphoryl chloride system afford either the new trihydroxyphenylbutenone derivatives 3b,c or dihydroxy-2,2-dimethyl-4-chromanones 4a-c in good yields. Compounds 3b,c can be cyclized in high yields to 4b,c in 5% sodium hydroxide solution. Regioselective O-alkylation of 4a-c leads to 5a-f in good yields. O-Alkylation of 5a-f , followed by reduction and dehydration, results in the formation of precocene 3 ( 7d ) and its regioisomer 7a-c,e,f . Methylation of 4a-c gives 6g-i . Subsequent reduction and dehydration affords precocene 2 ( 7h ) and its regioisomers 7g,i .     

Synthesis and Some Chemical Behaviour of Certain Substituted Thiosemicarbazides

Three new thiosemicarbazides (1 a-c ) were prepared from N-[4-phenyl-5-(2-thienyl)-1,2,4-triazol-3-yl]mercaptoacetohydrazide. Reaction of (1 a-c) with the appropriate phenacyl bromide afforded thiazoline derivatives (2 a-i) whereas their reaction with chloroacetic acid or maleic anhydride gave the corresponding thiazolidine derivatives (3 a,b) and (4 a,b) . Cyclodesulfurization of (1 a-c) with DCCD in toluene yielded 5-substituted-amino-1,3,4-oxadiazoles (5 a,b) , while their dehydration with PPA gave the corresponding 5-substituted-amino-1,3,4-thiadiazoles (6 a-c) . Six representative compounds were tested for their in-vitro antimicrobial activity against some pathogenic microorganisms, some of them were proved to be active.     

Mechanism of the cycloaddition-elimination reactions of 4-methyl-5-phenylimino-δ2-1,2,3,4-thiatriazoline with alkyl and aryl isothiocyanates

The formation of thiadiazolidines 3a-c and dithiazolidines 4a-c and 5a-b from the title reactions has been studied in detail under a variety of conditions. On the basis of kinetic measurements, isomerization studies and cross experiments a mechanism is proposed involving path (b) (Scheme 1) as the first step, followed by a series of isomerizations as shown in Scheme 3 .     

Synthesis and characterization of pyridine-based polyamido-polyester optically active macrocycles and enantiomeric recognition for D- and L-amino acid methyl ester hydrochloride

Five new chiral macrocycles, 3a-e, have been prepared by the acylation cyclization of chiral diamine dihydrobromide intermediates 2a-c with 2,6-pyridinedicarbonyl dichloride in highly diluted solution at room temperature. The chiral diesters 1a-c needed for the preparation of the macrocycles were obtained from condensation of corresponding N-(Z)-L-amino acids and 2,6-bishydroxymethyl pyridine in the presence of DCC and DMAP. The enantiomeric recognition of chiral macrocycles 3a-e for D- and L-amino acid methyl ester hydrochlorides has been characterized by fluorescence spectra, which indicate that some of them exhibited significant chiral recognition for the enantiomers of D- and L-amino acid methyl ester hydrochlorides. The stoichiometry and binding constants of 3a-L-Am(2) and 3c-L-Am(2) complexes have been determined. An X-ray analysis of the chiral macrocycle 3b show that the chiral ligand is rather rigid and strained.