The reaction of [60]fullerene with lithium fluorenide: Formation of a novel 1,4-adduct of [60]fullerene

Reaction of fullerene C-60 in THF with lithium fluorenide afforded 1-fluorenyl-1,2-dihyro[60]fullerene 2 after protonation. When the reaction time was extended to 24 h, an unusual adduct 3 was obtained, which had two fluorenyl groups attached at the 1,4-positions of a six-membered ring of C-60. The structure of 3 was confirmed by comparison of its properties with those of corresponding trimethylene-bridged adduct 5. Copyright (C) 1996 Elsevier Science Lt

Chiral analysis by electrospray ionization mass spectrometry/mass spectrometry. 2. Determination of enantiomeric excess of amino acids

The determination of enantiomeric excess (ee) of amino acids was achieved by investigating the collision-induced dissociation spectra of protonated trimers that were formed by electrospray ionization of amino acids in the presence of one of the following chiral selectors: L- or D-N-tert-butoxy-tert-carbonylphenlalanine, L- or D- N-tert-butoxycarbonylproline, and L- or D-N-tert-butoxycarbonyl-O-benzylserine, The protonated trimers were dissociated to form protonated dimers, and the observed dissociation efficiency r (i.e., the intensity ratio of protonated dimers to protonated trimers) for an enantiomeric mixture was found to be related to its ee value by the following equation: r = a + b/(c + ee), where a, b, and c were constants, A linear calibration plot was obtained by plotting r versus 1/(e + ee), where c was calculated with the MATLAB software, or by plotting 1/(r - r(0)) versus 1/ee, where r0 was the r value for the racemic mixture, The latter "two-reciprocal" method was more convenient for application. Another practical method for ee determination was the "three-point" method, whereby the ee of an unknown sample with a measured r value could be derived from the equation ee = 100{1/(r(L) - r(0)) - 1/(r(D) - r(0))}/{2/(r - r(0)) - 1/(r(L) - r(0)) - 1/(r(D) - r(0))}, With r(L) and rD being the r values for the enantiomerically pure Land D-forms of the sample, respectively, A calibration plot was not required. The ee determination was achieved with acceptable precision even for the worst case of acceptable chiral recognition with a particular chiral selector, suggesting that the ee determination of all 19 common amino acids could be achieved by the present method. The ee of a histidine sample was determined both by the two-reciprocal method, giving an error of 0.2\% ee (1.1\% relative error) and consuming only similar to5.3 nmol of sample, and by the three-point method, giving an error of 0.4\% ee and consuming only similar to2.3 nmol of sample, In the latter case, it took 27 min for the mass spectrometric measurements of the three calibration standards and an additional 9 min for the unknown sample. The direct ee determination of more than one amino acid in a mixture was also demonstrated in the study

Chiral recognition of amino acids by electrospray ionisation mass spectrometry/mass spectrometry

Chiral recognition of 19 common amino acids is achieved by investigating the collision-induced dissociation spectra of protonated trimers formed by electrospray ionisation of amino acids in the presence of one of the following chiral selectors: L- and D-N-tert-butoxycarbonylphenylalanine (BPhe), L- and D-N-tert-butoxycarbonylproline (BPro) and L- and D-N-tert-butoxycarbonyl-O-benzylserine (BBSer)

Separation of basic drugs with non-aqueous capillary electrophoresis

Capillary zone electrophoresis (CZE) was investigated in non-aqueous media. Efficient, rapid and versatile electrophoretic conditions were obtained with 20 mM ammonium acetate in acetonitrile-methanol-acetic acid (49:50:1). Using this non-aqueous medium, the baseline separation of nine morphine analogues, eleven antihistamines, eleven antipsychotics and ten stimulants could each be achieved in 6 min. The migration order observed was very different from one expected for an aqueous medium. The migration time repeatability for individual components was between 0.8 and 3.7\% R.S.D. The migration time-normalized peak area had a poor precision; however, with one of the components as an internal reference, the quantitative repeatability could be improved to between 2.2 and 9.1\% R.S.D. The precision data appeared to be instrument dependent, as excellent results could be obtained from an instrument with better evaporation and temperature control. Alternatively, much improved speed, efficiency and precision were also achieved with tetra-n-butylammonium tetrafluoroborate as the electrolyte, albeit with reduced selectivity. The effects of the electrolyte, non-aqueous medium and applied voltage on the separation are discussed

Chiral analysis by electrospray ionization mass spectrometry/mass spectrometry. 1. Chiral recognition of 19 common amino acids

Chiral recognition of 19 common amino acids was achieved by investigating the collision-induced dissociation spectra of protonated trimers that were formed from the electrospray ionization of amino acids in the presence of one of the following chiral selectors: L- or D-N-tert-butoxycarbonylphenlalanine L- or D-N-tert-butoxycarbonylproline, and L- or D-N-tert-butoxycarbonyl-O-benzylserine, The protonated trimers were dissociated to protonated dimers, and the intensity ratios of the protonated dimer (product ion) to the protonated trimer (precursor ion), i.e., the observed dissociation efficiency, was found to be strongly dependent on the chirality of the amino acids with respect to that of the chiral selectors. The results showed that the chirality of all 19 common amino acids can be definitely differentiated. The method was demonstrated as rapid, sensitive, precise, robust, and requiring no reference standards and only minimal sample preparation. The chirality of all three amino acids in a mixture was determined without prior separation of the amino acids, consuming only 70 pmol of sample and requiring only similar to 14 min of mass spectrometric measurements. A cyclodipeptide with unknown chirality was determined to be cyclo-(L-Pro-L-leu) by acid hydrolysis followed by the present method, and the results were consistent with the physiochemical properties and NMR data of the compound. This study suggested that ESI-MS/MS can be a promising approach for the chiral recognition of other compounds

The solid-phase reaction of [60]fullerene: Novel addition of organozinc reagents

Reaction of ethyl bromoacetate and zinc with [60]fullerene in the absence. of any solvent, followed by quenching with acid affords 1-ethoxycarbonylmethyl-1,2-dihydro[60]fullerene along with other minor byproducts including 1,4-bis(ethoxycarbonylmethyl)-1,4-dihydro[60]fullerene; a detailed reaction mechanism is proposed

High pressure synthesis of cycloadduct of fullerene C-60 with 2H-pyran-2-one

Under high pressure conditions, fullerene C-60 smoothly reacts with 2H-pyran-2-one to give a [4+2] cycloadduct, which can be reduced to an alcohol derivative

Synthesis and properties of dialkyl derivatives of di[60]fullerenylbutadiyne and di[60]fullerenylacetylene: The Buckydumbbells

The dumbbell-type C-60 dimers connected by a butadiyne or an acetylene spacer were synthesized and fully characterized. The cyclic voltammetry indicated that the electronic interaction between two C-60 cores is negligibly small. Copyright (C) 1996 Elsevier Science Lt

Synthesis of disubstituted 1,2-dihydro[60]fullerenes with well-defined structure by addition of 1-alkoxy-1-chloroethanes to 2-(1-octynyl)-1,2-dihydro[60]fulleren-1-ide ion

We report the preparation of disubstituted 1,2-dihydro[60]fullerenes having functional groups, namely 1-(1-octynyl)-2-(1-isobutoxyethyl)-1,2-dihydro[60]fullerene and 1-(1-octynyl)-2-[1-(2-acetoxyethoxy)ethyl]-1 ,2-dihydro[60]fullerene, by coupling 2-(1-octynyl)-1,2-dihydro[60]fulleren-1-ide ion with carbon electrophiles derived from vinyl ethers. The structure and redox properties of the products were examined by H-1 and C-13 NMR spectra and cyclic voltammetry

REACTION OF C60 WITH CHLOROPHENYLDIAZIRINE - SPECTRAL AND ELECTRONIC-PROPERTIES OF THE C60-CHLOROPHENYLCARBENE 1-1 ADDUCT

A reaction of C60 with an equimolar amount of chlorophenyldiazirine in refluxing toluene afforded the C60-chlorophenylcarbene 1:1 adduct in 37\% yield. The adduct was shown to have the cyclopropane structure by C-13 NMR and exhibited reversible reduction waves at the potential about 0.1 V more negative and an irreversible oxidation peak at nearly the same potential as compared with those of C60 itself