Selective syntheses of novel highly functionalized β-aminocyclohexanecarboxylic acids

Highly functionalized β-aminocyclohexanecarboxylate regio- and stereoisomers were synthetized from racemic unsaturated bicyclic β-lactams via enzymatic resolution, selective transformation of the C–C double bond by stereoselective epoxidation, and regioselective oxirane ring opening with azide or cyanide as nucleophile.     

Preparative separation of fullerene adducts by liquid chromatography on polystyrene gel

Summary The preparative separation of numerous fullerene adducts by liquid chromatography on polystyrene gel is described. These adducts can be resolved on a scale of 10–40 g/day on a 600×20 mm column. Both toluene and chloroform can be used as mobile phases; toluene offers better solubility for the adducts and chloroform better peak resolution.     

Strategic applications of Baylis-Hillman adducts to general syntheses of 3-nitroazetidines

A novel one-pot highly diastereoselective synthesis of substituted 3-nitroazetidines via an anionic domino process is described. The synthesis involves a high yielding annulation of Baylis-Hillman alcohols and their aldehydes with either N-aryl/tosylphosphoramidates or N-aryl/tosylphosphoramidates in combination with a task-specific ionic liquid [bmim][X-Y] to afford the corresponding 1,2,3-tri- and 1,2,3,4-tetrasubstituted azetidines, respectively. Plausible mechanisms for the formation of various 3-nitroazetidines have been suggested.     

The preparation and characterisation of novel polyether gels

Poly(ethylene oxide)s end-capped with n-alkane chains (C₁₆-C₂₁) have been found to form stable gels in aqueous media. The crosslinks are believed to occur through association of the n-alkane chains. The dependence of the degree of swelling of the gels on the lengths of the alkane and poly(ethylene oxide)(M_n= 10000, 20000 and 30000) chains were studied. Degrees of swelling have been compared with results predicted by simple network theory.     

Maerocyelic polyether sulfide syntheses. The preparation of thia-crown-3,4, and 5 compounds

Macrocyelic polyether sulfides have been prepared by reacting an oligoethylene glycol dichloride with a dithiol or sodium sulfide in ethanol. The trivial naming system for these compounds is an extension of the trivial crown nomenclature (5). A thia prefix is used to show that sulfur atoms have replaced ether oxygen atoms in the polyether ring. The following new compounds were prepared: 1-thia-(15-crown-5) (II) 1,4-dithia-(15-crown-5) (III) 1,7-dithia-(15-crown-5) (IV) 1,4-dithia-(12-crown-4) (VII) 1,4,7-trithia-(12-crown-4) (VIII) 1-thia-(9-crown-3) (IX) and 1,4-dithia-(9-crown-3) (X). Four other previously reported maerocyelic polyether sulfides were also prepared. The symmetry of the nmr spectra of these compounds gives added evidence for the proposed ring structures.     

Synthesis of fluorous fullerene adducts: reversible solubilization of fullerenes in perfluorinated solvents

Fullerene (C60) Diels-Alder adducts with perfluoroalkylated 1,3-cyclopentadiene (1a,b) were synthesized and studied. The perfluoroalkylated cyclopentadiene was found to be less reactive toward C60 than cyclopentadiene itself, possibly because of the electron-withdrawing effect of the side chain. Because of the same effect, the temperature of the retro-Diels-Alder reaction for the fluorinated adducts was lower (70 degrees C) than the reported value (95 degrees C) for the cyclopentadiene adducts of C60. Higher adducts of the fluorous diene and C60 were found to be soluble in perfluorohexane and to show visible partitioning between organic (toluene) and fluorous phases. Also, the Diels-Alder addition of the fluorous diene was accompanied by extensive oxidation of the fullerene core, as revealed by MALDI-TOF data.     

Synthesis of fullerene adducts with terpyridyl- or pyridylpyrrolidine groups in trans-1 positions

Two C(60) hexakis-adducts (2 and 3) were synthesized by using a protection-deprotection strategy. The symmetric fullerene tetrakis-adduct 8 was obtained by anthracene removal from the hexakis-adduct 7. Reaction of 8 with terpyridylglycine or pyridylglycine afforded two hexakis-adducts, 2 and 3. By using the retro-cyclopropanation reaction, the four malonate addends located on the equatorial belt of the hexakis-adducts were removed to afford two trans-1 bis-adducts, 4 and 5, with terpyridyl- or pyridylpyrrolidine groups. The structures of 2 and 3 were confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and (1)H, (13)C, and COSY NMR, and UV-visible spectroscopy. The cyclic voltammograms of fullerene multiadducts 2, 3, and 9 show irreversible reductions. Self-assembled monolayers (SAMs) of 1 and 3 were formed on gold surfaces through nitrogen adsorption. SAMs of 3 represent the first example of a fullerene hexakis-adduct formed on gold surfaces through nitrogen adsorption. Controlled potential electrolyses (CPE) were conducted to prepare trans-1 bis-adducts 4 and 5 modified with terpyridyl and pyridyl groups.     

Selective mono N-alkylations of cyclen in one step syntheses

In this Letter, we describe selective one step mono N-alkylations of cyclen (1,4,7,10-tetraazacyclododecane) using a range of functionalized alkyl halides. This ‘easy to use’ synthesis gives rise to mono-derivatives of cyclen from various alkyl halides or, when using alkyl dihalides, bis-cyclen derivatives, where the alkyl group links two cyclen macrocycles together. While the reaction conditions require the use of 1:4 stoichiometry (alkyl halide:cyclen), any unreacted cyclen can be recovered with an aqueous extraction and successfully reused. This procedure was found to be quite versatile, being particularly well-suited for cyclen targets bearing protected thiol groups, as well as α-chloroamide-derived chromophores; such cyclen pendant chromophores are employed as antennae for lanthanide luminescence probes and sensors.     

Selective extraction of organic compounds as ion-pairs and adducts

Selective and easily regulated systems for extraction of organic compounds as ion-pairs and/or adducts are presented. The effect of different kinds of hydrophobic agents that give adducts in the organic phase are demonstrated: mesitylene for nitrophenols, ethyl acetate and diethyl ether for hexestrol (diphenol), lipophilic alcohols for organic ammonium ion-pairs, dibenzo-18-crown-6 for ion-pairs of primary ammonium ions, HDEHP for hydrophilic aminophenols (adrenaline, isoproterenol, synephrine). It is shown that the extraction selectivity decreases with increasing content of the complexing agent in the adduct. The influence of the hydrogen-bonding character of the counter-ion and the organic solvent on the selectivity of ion-pair extractions is demonstrated with ammonium compounds (nortriptyline, amitriptyline and N-methylainitriptyline) and inorganic anions. Highly hydrophilic anionic compounds (e.g., glucuronides, cholic acid derivatives) can be extracted into chloroform as ion-pairs with large quaternary alkylammonium ions. The extraction efficiency of the cation increases with the number of methylene groups to a limit which is due to co-extraction of other sample components (e.g., buffer anions).     

The syntheses and structures of iron carbonyl adducts of tricoordinated hypervalent phosphorus compounds

The hypervalent phosphorus compound 3,7-di-t-butyl-5-aza-2,8-dioxa-1-phosphabicyclo[3.3.0]octa-2,4,6-triene(ADPO), forms a monosubstituted adduct, ADPO·Fe(CO)₄, by direct reaction of 10-P-3 ADPO with Fe₂(CO)₉ or Fe(CO)₅, as well as by reaction of 1,1-dichloro-3,7-di-t-butyl-5-aza-2,8-dioxa-1-phosphabicyclo[3.3.0]octa-3, 6-diene(ADPO·Cl₂) with Na₂[Fe(CO)₄]. The X-ray crystal structure of ADPO·Fe(CO)₄ shows that ADPO is coordinated to the iron through the phosphorus. The phosphorus of the adduct has a tetrahedral 8-P-4 geometry in contrast to the planar T-shaped geometry of uncomplexed 10-P-3 ADPO. Ultraviolet photolysis of ADPO·Fe(CO)₄ yields the disubstituted species (ADPO)₂·e(CO)₃ wherein ADPO has dimerized via P–O bond cleavage to form a bidentate (ADPO)₂ ligand containing a 10-membered ring that bridges axial and equatorial positions at the trigonal bipyramidal iron center.     

Photophysical properties of novel water soluble fullerene derivatives

The spectroscopic and photophysical properties for a series of bis-adduct derivatives of C₆₀ have been studied using a combination of time-resolved and steady state techniques, including picosecond single photon counting and laser flash photolysis. The electronic absorption and fluorescence spectra are red shifted with respect to those of C₆₀. As with the parent fullerene, the main deactivation channel of the excited singlet state is intersystem crossing with the yields of singlet oxygen ranging from 0.63 to 0.97. Our results demonstrate that the photophysical properties depend on the addition pattern of the addends.     

Synthesis and characterization of adducts of p-azidostyrene derivatives to fullerene C_(60)

Fullerene C60 reacted with p-azidostyrene derivatives in refluxing chlorobenzene,yielding monoadducts 2a and 2d as well as diadduct 2c with aziridine structure at 6/6-ring junctions.Experimental results showed that the addition of the second azide to the monoadduct was regioselective.The diadduct,of Cs symmetry in C60 moiety,was unstable by opening to be 1,6-imido[10]annulene structure.     

A novel carbohydrate-derived side-chain polyether with excellent protein resistance

A novel carbohydrate-derived side-chain polyether was synthesized as a new biomaterial by condensation polymerization of monomers derived from natural occurring carbohydrates. Surface plasmon resonance spectroscopy studies demonstrated that this side-chain polyether has excellent resistance to nonspecific protein adsorption. The protein resistant capability of the side-chain polyether is comparable to that of oligoethylene glycol, a main-chain polyether that is, to date, the best protein resistant material. In addition to the excellent biocompatibility, the new polymer also combines biodegradability and functionalizability. With these combined good properties, this side-chain polyether is envisioned as a new biomaterial for many potential biomedical applications.     

Multifunctionalised cationic fullerene adducts for gene transfer: design, synthesis and DNA complexation

Cationic poly-N,N-dimethylfulleropyrrolidinium derivatives have been designed and synthesised to complex plasmid DNA for gene delivery.     

Prolonged charge-separated states of starburst tetra(diphenylaminofluoreno)[60]fullerene adducts upon photoexcitation

Construction of starburst C60(>DPAF-C9)4 pentads was coupled with the use of highly fluorescent diphenylaminofluorene-C9 (DPAF-C9) addends as donor components in conjunction with the fullerene acceptor during single-photon excitation processes. High quantum yields (PhiCS) of charge-separation processes in the range 0.83-0.90 for C60(>DPAF-C9)n (n = 1, 2, or 4) were obtained in the formation of C60*-(>DPAF*+-C9)(>DPAF-C9)n-1 transient states. The lifetime of the radical ion-pairs (tauRIP) was found to be 900 ns for starburst C60(>DPAF-C9)4 (3) samples, which is 6-fold longer than that of the linear analogue C60(>DPAF-C9) (1), with a ca. 2 times increase of the charge-separation rate (kCS) compared to that of 1. These data implied the important role of sterically hindered DPAF-C9 pendants arranged in a starburst-like environment that encapsulates the central C60 core on extending the tauRIP. We interpreted the phenomena by the occurrence of intramolecular migration or exchange of electron or positive charge among multiple DPAF-C9 pendants of C60*-(>DPAF*+-C9)(>DPAF-C9)n-1, which gives an increased rate in charge generation and delayed charge recombination.     

A novel phthalocyanine with two axial fullerene substituents

A silicon phthalocyanine with two axial fullerene substituents was synthesized, and its electrochemical, absorption- and film-properties were characterized.     

Synthesis of [60]fullerene adducts bearing carbazole moieties by Bingel reaction and their properties

Carbazole-linked [60]fullerene adducts were successfully prepared by the Bingel reactions using carbazole derivatives bearing one or two ethyl malonate moieties. In the latter cases, specific bisadduct regioisomers were obtained, depending on the spacer unit between two ethyl malonate moieties. [reaction: see text]     

Synthesis of novel fullerene amino acids and their multifullerene peptides

[60]-Fullerene functionalized amino acids with 4-6 methylene spacers from α-carbon to the nitrogen atom of fulleropyrolidine and corresponding multifullerene peptides have been synthesized.     

Applications of aziridinium ions. Selective syntheses of beta-aryl-alpha,beta-diamino esters

[formula: see text] alpha,beta-Diamino esters are readily prepared through stereospecific and regioselective opening of an aziridinium ion intermediate with a variety of amines. The aziridinium ion is generated from the epoxide in two steps.