Hydroxy-, derivatives mass spectrometry

The relative stereochemistry of hyperaspine 93 was determined by 2-D NMR spectroscopic and mass spectrometry (MS) methods. It has a m-fused bicyclic conformation 93a <2001TL4621>. The trans-fused one is disfavored by an axial pentyl group at C-8 and by a destabilizing dipole-dipole interaction between the N- and O-atoms, which does not exist in the alternative //.(-conformation. The geminal coupling constant of C( 1 )H2 in 93 (11.0 Hz), and that of its 6-hydroxy derivative (11.2 Hz), indicates that they exist preferentially in / //-conformations, whereas their 6-epimers adopt trans-conformations (9.3 and 8.4 Hz, respectively) <2005EJ01378>. Nuclear Overhauser enhancement spectroscopy (NOESY) studies also confirmed the stereochemistry of 93 by the marked nuclear Overhauser effect (NOE) correlation between H-3 and H-4a <20030L5063>. 

The ionization potentials, using mass spectrometry, for both 2-hydroxy-and 3-hydroxythiophenes have been compared with data for compounds derived from either tautomeric form in order to analyze the tautomeric composition.124 125 In the 2-hydroxy-substituted system the enol isomer could not be detected. Of the two possible unsaturated lactones the oc,/l-unsaturated form was the major isomer. In the 3-hydroxy-substituted case both the oxo form and the enol form are important. The position of the equilibrium was compared with those of the corresponding furan and sele-nophene systems for both isomers. 

The fluorines in fluorinated C60 can be displaced by a variety of nucleophiles. Furthermore, fluorinated C60 derivatives are likely to be synthetically useful because they are both more reactive, and more soluble than other halogenated derivatives (Taylor et al. 19925). They thus react readily with water, which negates their use as lubricants (Taylor et al. 1992 a). Mass spectrometry indicates that the products contain numerous hydroxy groups and epoxide links (probably from elimination of either HF or H20 from adjacent groups). An addition-elimination mechanism is probably involved since the normal SN2 process is ruled out because backside attack (Taylor et al. 19926) is impossible. 

Melphalan has been converted to its trimethylsilyl derivative with bis(trimethylsilyl)acetamide and has been analyzed by GC on a 1.8 m x 3 mm column packed with 2.5% (w/w) SE-54 on acid-washed, silanized Chromosorb W (80-100 mesh) at 210° (injector temperature, 250° flame ionization detector temperature, 215°) using nitrogen as the carrier at 30 ml/min. The order of elution from a partly hydrolyzed mixture was melphalan, mono-hydroxy-derivative VI and di-hydroxy-derivative VII (Scheme III). The same elution order was obtained on a SE-30 column it was reversed on a more polar liquid phase (OV-17). Identification of the peaks was done by mass spectrometry [52]. 

Demethoxyabresoline (67) was obtained as a noncrystalline solid. Spectroscopic investigation revealed the presence of a phenolic OH, a 1-phenyl-quinolizidine system, and a trans-cinnamyl group. The stereochemistry at C-l, C-3, and C-5 was the same as in abresoline. The molecular formula C25H29N05 was established by mass spectrometry. The presence of fragment ions at m/e 259 (M —164) and 258 was characteristic of p-hydroxy-cinnamyl esters of the phenylquinolizidol (63a). The assigned structure 68 was confirmed by basic hydrolysis to 63a and p-hydroxycinnamic acid as well as by catalytic hydrogenation to a known dihydro derivative (52). 

Other Fission Processes - The results of the irradiation of benzyl acetate and 3,5-dimethoxybenzyl acetate have been analysed using membrane introduction mass-spectrometry. Irradiation of the acid derivative (136) under nitrogen in methanol brings about the formation of the corresponding ester. The authors suggest that this process is the result of CO bond fission and the liberation of a hydroxy radical. Subsequently this is trapped by methanol as the ester (137). 

The combination of chromatography/mass spectrometry with MS/MS methods can in fact markedly enhance the analytical performance of the identification of phenols. This was demonstrated in the case of hydroxy aromatic components in coal-derived liquids. The analytical performance can be further improved by using chemical derivatization, as also shown in an MS/MS study of some methylphenols and methylnaphthols. In the course of GC/MS/MS analytical studies on nonylphenol in biological tissues, derivatization proved to be favourable in an indirect way The El mass spectrum of nonylphenol... 

Calix[n]arenes are cyclic condensation products of para-substituted phenol derivatives and formaldehyde [29], They are highly interesting for the development of sensitive coatings due to their conformational flexibility and the ease by which they may be modified chemically. Chemical modification can be done either in the meta position, or by reactions at the hydroxy group. In this way, bulky substituents [30], chelating substituents [31], aromatic residues [32], crown ethers [33,34], peptides [35,36], etc. can be introduced. A first approach to combinatorial synthesis of calix[4]arene receptors has been published by Reinhoudt and co-workers [37,38], who prepared calixarenes with different substituents. In solution, these calixarenes lead to formation of hetero-oligomers with barbiturates, and these hetero-oligomers were detected by MALDI-TOF mass spectrometry and H-NMR spectroscopy. 

Van Kuijk, F.J.G.M., Thomas, D.W., Stephens, R.J. and Dratz, E.A. (1986) Occurrence of 4-hydroxy-alkenals in rat tissues determined as pentafluorbenzyloxime derivatives by gas chromatography-mass spectrometry. Biochem. Biophys. Res. Commun. 139 144—149. 

The in vivo administration of diethylni-trosamine (Et2N-N=0) to mice reportedly generates an alkylated porphyrin that was tentatively identified by mass spectrometry as A-(2-hydroxy-ethyl)protoporphyrin IX . In vitro studies with rabbit liver microsomes and purified P450 enzymes have independently shown that P450 oxidizes diethylnitrosamine to ethylene . Although not actually demonstrated, the proposed N-(2-hydroxyethyl) porphyrin adduct is likely to be derived from P450 enzymes inactivated by the ethylene metabolically generated from diethylnitrosamine (see Section 3.3.1). 

As a result of the reported antimicrobial action of extracts of the hop tree, Ptelea trifoliata, Mitscher et al. (54) investigated the aboveground constituents and found that the sole active agent was a new phenolic quinolinium derivative pteleatinium salt. The alkaloid was isolated as the chloride, C16H20NO4CI, and was shown to be the 8-hydroxy-Af-methyl-platydesminium salt (38) on the basis of IR, UV, NMR, and mass spectrometry and of correlation with known quinoline alkaloids. Thus, pyridine effected demethylation to the 4-quinolone 39 which, with diazomethane, was converted into (+)-balfourodine (12), while methylation of pteleatinium chloride with methyl iodide and sodium carbonate gave O-methyl-... 

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