Synthesis of a silk-inspired peptide-oligothiophene conjugate

The first example of an oligothiophene-peptide conjugate, which was obtained by solid-phase acylation of a resin-bound silk-inspired oligopeptide sequence with a carboxylic acid functionalized regioregular tetra(3-hexylthiophene) derivative, is reported.     

Preparation via Diastereoselective Hydrogenation,Absolute Conformation and Configuration of Exogeneous Anabolic Zeranol ((3S, 7R)-3,4,5,6,7,8,9,10,11,12-Decahydro-7,14,16-trihydroxy-3-methy-1H-2-benzoxacyclotetradecin-1-one)

Hydrogenation of the ketone group in di-O-benzylderivative ( 8 ) of the known macrocyclic lactone zeralenone ( 7 ) using a novel chiral borane complex 3 . BH₃, prepared in situ, proceeded at lower temperatures with moderate diastereoselectivity (～40%, d. e. at ?60°). Unsaturated diastereomers 9 and 10 were separated, and 9 converted into zeranol ( 11 ), a known anabolic agent. Restricted conformational mobility at lower temperatures is assumed for the intermediate 8 on the basis of the temperature-dependent CD spectra of its acetyl congeners 18 and 19 . X-Ray structure analysis of 7-O-acetylderivative ( 13 ) of 11 revealed the (R)-configuration at C(7). Two crystallographically independent H₂O molecules are involved in the H-bonds, one of them (O(21)) rises the helices of the molecules of 13 along b. Small positive torsional angle [C(16)-]C(161)-C(1) [=O] (+19.3°), transoid(E) conformation of the lactone group, and nearly achiral arrangement of the C(11)-C(12) bond (torsional angle [C(11)-]C(12)-C(121)[C(161)] is ?93°) are the main conformational features that differentiate the macrocylic RAL (resorcinic-acid lactone) derivatives from the 6-membered lactone derivative 20 , studied earlier by CD. Consequently, the rules developed for the CD effects within conjugation band (around 270 nm), and n→π* band (around 255 nm) of the latter compound, cannot be applied the macrocyclic lactones.     

Identification of cis/trans isomers of methyl ester and oxazoline derivatives of unsaturated fatty acids using GC–FTIR–MS

Identification of cis/trans isomers of unsaturated fatty acids cannot usually be achieved by GC-MS (gas chromatography-mass spectrometry) without reference substances. In this study a GC-FTIR-MS system (gas chromatography-Fourier transform-mass spectrometry) was used to identify fatty acid methyl esters (FAMEs) and differentiate between the cis/trans isomers. Besides methyl esters, 2-alkenyl-4,4-dimethyloxazoline derivatives (DMOX), which have been used to locate double bond positions of unsaturated fatty acids, were examined with respect to their suitability for cis/trans differentiation. A combined GC-FTIR-MS system with a wide band (4000–550 cm^?1) mercury cadmium telluride (MCT) detector was used in series and parallel to identify 31 reference unsaturated fatty acids, including 7 pairs of cis/trans isomers. Serum samples of healthy persons and commercially available fish oil were analyzed as examples of complex mixtures. Using splitless injection the detection limit for the less sensitive IR detector was 25 ng/μl in case of the weak cis and trans bands. In the FTIR spectra cis/trans isomers were identified by analysis of bands arising from C? H out-of-plane (oop) bending: for both the FAME and DMOX derivatives cis-1,2-disubstituted double bonds give a strong band near 720 cm^?1 and the corresponding trans isomers near 967 cm^?1. cis Isomers could be identified further by a band at 3012 cm^?1. With the combined data of the GC-FTIR-MS system it is now possible to identify polyunsaturated fatty acids with regard to the discrimination of cis/trans isomers.     

Stereoisomeric flavor compounds,part LVIII: The use of heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as a chiral stationary phase in flavor analysis

The characteristics of the new chiral stationary phase heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin are outlined and compared with permethyl- and perethyl-β-cyclodextrins.     

Characterisation of inhibitors of acetylcholinesterase by an automated amperometric flow-injection system

Acetylcholinesterase was immobilised on magnetic particles and integrated in a flow-injection system via a magnetic reactor. Enzyme activity was determined amperometrically using acetylthiocholine chloride as enzyme substrate. This system was applied to enzyme inhibition tests. Inhibition constants and lower detection limits were determined for carbofuran, paraoxon, malaoxon and paraoxon-methyl. The resulting data were compared to those obtained with a photometric test, i.e. the determination of thiocholine via its reaction with the Ellman's reagent 5,5'-dithio-bis-2-nitrobenzoic acid using the same flow system. As they correlated well to those reported for the native enzyme the flow-injection analysis device can be applied to automated determination and characterisation of enzyme inhibitors.     

Simultaneous determination of acidic,basic and alcoholic substances relating to monoamine hormones and metabolites in biological material by mass fragmentography (GC/MF)

A method is described for the simultaneous quantitative determination of monoamines and related compounds from urine and brain tissue samples in the pg-range, using a GC/MF instrument LKB-2091 provided with a multiple ion detection (MID) system and capillary columns. The simultaneous detection of “fingerprints” with fourteen and more compounds during one single GC run was achieved after the intoduction of “time gates” for the detection of the different characteristic masses. Several modifications to the LKB equipment permitted exact reproducibility of retention times, which is essential for the use of “time gates”. The detection of “fingerprints” with these acidic, basic and alcoholic substances was achieved by the extraction of the dried biological samples with silylating agents.     

Fundamental systems of units in biquadratic parametric number fields

Let D, d be integers with D > 0, d dividing D and d square free and let α and β be the two roots of the quadratic equation x² ? Dx ?d = 0. Suppose (α ? β)² = D² + 4d > 1 and α² + β² = D² + 2d be square free. Introduce $\text{e =}\text{(ω + α)}\text{β}$ and $\text{u =}\text{(ω + β)}\text{α}$, where $\text{ω =}\text{a}{}^2\text{+ β}{}^2$. Then it is proved that e, u and θ form a fundamental system of units in the field $\text{Q}\text{D}{}^2\text{+ 4d}\text{,}\text{D}{}^2\text{+ 2d}$, where

$\text{θ=}\text{α}\text{β}\text{if}\text{d ≠ ± 1}\text{and}\text{(D,d) ≠ (5,?5)}$

$\text{θ=}\text{α}\text{β}\text{=}\text{1+}\text{5}\text{2}\text{if}\text{(D,d)=(5,?5)}$

$\text{θ=α}\text{if}\text{d = ± 1}\text{and}\text{(D,d) ≠ (3,?1)}$

$\text{θ=}\text{α=}\text{1+}\text{5}\text{2}\text{if}\text{(D,d)=(3,?1)}$