Robert Engel

Preparation of ionic liquid based solid-phase microextraction fiber and its application to forensic determination of methamphetamine and amphetamine in human urine

A new solid-phase microextraction (SPME) procedure using an ionic liquid (IL) has been developed. Reusable IL-based SPME fiber was prepared for the first time by fixing IL through cross-linkage of IL impregnated silicone elastomer on the surface of a fused silica fiber. 1-Ethoxyethyl-3-methylimidazloium bis(trifluoromethane) sulfonylimide ([EeMim][NTf(2)]) ionic liquid was employed as a demonstration and the prepared fiber was applied to the forensic headspace determination of methamphetamine (MAP) and amphetamine (AP) in human urine samples. Important extraction parameters including the concentration of salt and base in sample matrix, extraction temperature and extraction time were investigated and optimized. Combined with gas chromatography/mass spectrometry (GC/MS) working in selected ion monitoring (SIM) mode, the new method showed good linearity in the range of 20-1500 microg L(-1), good repeatability (RSD<7.5% for MAP, and <11.5% for AP, n=6), and low detection limits (0.1 microg L(-1) for MAP and 0.5 microg L(-1) for AP). Feasibility of the method was evaluated by analyzing human urine samples. Although IL-based SPME is still at the beginning of its development stage, the results obtained by this work showed that it is a promising simple, fast and sensitive sample preparation method.

Preparation and investigation of antibacterial carbohydrate-based surfaces.

Surfaces bearing carbohydrate units have been modified in a two-step process to incorporate functionalities (lipophilic with polycationic units) that bear antibacterial activity. The effectiveness of these modified surfaces for antibacterial action against a series of seven Gram-positive and Gram-negative bacteria are reported.

An Improved Direct Oxidation of Alkyl Halides to Aldehydes

The oxidation of alkyl chlorides and bromides with dimethyl sulfoxide has been performed in the presence of sodium iodide. This method allows a convenient one-step procedure for the preparation of ...

A NOVEL SYNTHESIS OF 1-AMINOALKYLPHOSPHONATES

Abstract A nover route has been devised ofr the preparation of a series of 1-aminoalkylphosphonate deisters, precursors to analogues of a-amino acids. The route involves a ficile bromine subsititution at the 1-position of alkylphonate diesters using N-bromisuccinimide, followed by azide ion displacement and catalytic hydrogenolysis.

Isosteres of natural phosphates. 10. synthesis of analogues related to glycerol 3-phosphate

Abstract We have synthesized a pair of diastereoisomers of 1,3,4-trihydroxybutyl-1-phosphonic acid. Both bear the same absolute configuration as sn -glycerol 3-phosphate at the 3-position, but differ in configuration at the site adjacent to phosphorus. These have been synthesized by the regiospecific and stereospecific reaction of a chiral hydroborating agent with a β-substituted vinylphosphonate.

Rabbit muscle l-glycerol-3-phoshate dehydrogenase: Substrate activity of 3,4-dihydroxybutyl 1-phosphonate and 4-hydroxy-3-oxobutyl 1-phosphonate

Abstract The phosphonic acid analogs of glycerol 3-phosphate, 2,3-dihydroxypropyl 1-phosphonate and 3,4-dihydroxybutyl 1-phosphonate, were examined as substrates for the rabbit muscle NAD-linked glycerol-3-phosphate dehydrogenase ( l -glycerol-3-phosphate: NAD oxidoreductase, EC 1.1.1.8). The three-carbon analog was completely inert while the four-carbon analog was oxidized at approximately the same rate and had nearly the same K m (240 μM for glycerol 3-phosphate compared to 190 μM for 3,4-dihydroxybutyl 1-phosphonate) as the natural substrate. The rate of reduction of dihydroxyacetone phosphate was approx. 25 times faster than that for its analog, 4-hydroxy-3-oxobutyl 1-phosphonate. This difference was not due to a difference in K m values since the value for the natural substrate is 130 μM compared to 182 μM for the analog. The difference in rate does not appear to be due to a difference in the acidity of the phosphonate as compared to the natural substrate.

Polycations. IX. Polyammonium derivatives of cyclodextrins: syntheses and binding to organic oxyanions

A series of polycationic derivatives of α- and β-cyclodextrin have been synthesized. Their interactions for inclusive binding of series of organic phosphorus oxyanions and anions of biological α-amino acids have been investigated using NMR techniques. Determinations of association constants and orientation of guest anion binding to the host polycationic cyclodextrin derivatives have been performed.

Polycations. 4. Synthesis and antihydrophobic effect of polycationic strings

Two categories of polycationic “strings” have been synthesized and investigated for their effect on the aqueous solubility of hydrophobic organic compounds (benzene and 4-bromotoluene, the latter discussed here). Polycationic “strings” are compounds in which cationic sites (quaternary ammonium sites) are incorporated into the covalent structure along a linear chain with free-floating associated anions. The categories are: 1) defined length chains consisting of quaternized dabco units connected by intervening lengths of methylene groups, terminating with ω-alkanol units, and 2) α,ω-dimethylaminoalkane units quaternized with chain extending ω-alkanol units. The observed antihydrophobic effect depends on the total charge, the length of the charge-intervening linkages, and the terminating groups.

Phosphonium cascade molecules

Cascade molecules have been synthesized in which the initiation core and branch points of the cascade structure are quaternary phosphonium ion sites.

The synthesis of phosphonic acid and phosphate analogues of glycerol-3-phosphate and related metabolites

Abstract A convenient route is described for the preparation of the isosteric phosphonic acid analogue of glycerol-3-phosphate, 3,4-dihydroxybutyl-1-phosphonic acid, in both enantiomeric forms and the racemic modification, starting with readily available materials. The (S)-enantiomer, that of absolute configuration corresponding to that of sn-glycerol-3-phosphate, has been found to be a growth inhibitor of several bacteria at low concentration. The synthetic route described is of particular value as it facilitates the preparation of a series of phosphonic adds and phosphates of related structure, in their enantiomeric forms, which are also of interest for metabolic regulation. These include the 3,4-epoxybutyl-1-phosphonate and a phosphate analogue of glycerol-3-phosphate with the related homodiglyceride. Investigations are continuing in the evaluation of the biological activity of the materials synthesized. A method is also described for the synthesis of the carbon-14 labelled 3-carboxy-3-hydroxybutyl-1-phosphonic acid, an analogue of phosphoglyceric acid known to serve as a substitute for the natural material in several biochemical processes.