Access to isocarbacyclin derivatives via substrate-controlled enolate formation: total synthesis of 15-deoxy-16-(m-tolyl)- 17,18,19,20-tetranorisocarbacyclin

[reaction: see text] We describe a convergent and flexible synthesis of 15-deoxy-16-(m-tolyl)-17,18,19,20-tetranorisocarbacyclin (15-deoxy-TIC), a simple isocarbacyclin derivative. The synthesis takes advantage of two key step reactions: a regioselective deprotonation of the described ketone under substrate control which is then trapped, as the enol triflate, to generate the C6-C9alpha endocyclic double bond, followed by an sp2-sp3 Pd-catalyzed cross-coupling reaction (C5-C6) with a suitable primary alkyl Grignard reagent. Introduction of the C13-C14 (E)-double bond in the omega-side chain is performed by the Julia-Kocie?ski olefination.     

Automated determination of fatty acid methyl ester and cis/trans methyl ester composition of fats and oils

The determination of the fatty acid composition (as methyl esters, FAMEs) of fats and oils and their cis/trans (CTME) distribution requires a simple, but manual and time-consuming sample preparation. The so-called BF3 method is often the preferred procedure. Because FAME/CTME analyses are encountered very frequently in the food industry, an automated, robot-based alternative is proposed which uses the sodium methylate procedure. After sample weighing and the (manual) addition of heptane (2 min), a XYZ robotic autosampler is used for all remaining work, which includes reagent addition, agitation, sample settling and the final injection into the gas chromatograph (10 min). The performance of the sodium methylate and BF3 methods are compared by analysing some 30 oil and fat samples. The novel procedure is much faster (less than 15 min versus ca. 1 h) and manual sample handling is drastically decreased. The experimental results obtained with the two methods frequently are the same, while small differences can be explained by (known) differences of the two methods in the conversion of minor oil/fat constituents, such as free fatty acids, wax esters and sterol esters. In case of FAME analyses, a hot injection is to be preferred over a cold injection. The RSDs of the peak areas were 1.5% for the major fatty acids to 11% for peaks that were just above the noise level. The detection limit were approximately 0.03%.     

Observation of Diastereomers by 199Hg NMR

The diastereomeric parts of HgP bonded Hg[P(O)(OBuⁿ)ph]₂ give rise to different ¹⁹⁹Hg NMR patterns. No enantiomeric discrimination occurs in the synthesis. Ligand redistribution reactions prevent the separation of the diastereomers.     

Über die Mischbarkeit von UN mit LaN,CeN, PrN,NdN, SmN,GdN, DyN,und ErN

X-Ray studies of the mixed nitride phases indicate complete miscibility in all cases. Lattice parameters generally showed negative deviations from the additivity rule.

Teilauszug aus der Dissertation des Dipl.-Ing.J. Waldhart an der Technischen Universität Wien, Österreich.     

Investigation of parameters affecting the on-line combination of supercritical fluid extraction with capillary gas chromatography

Two different injectors, a split/splitless injector and a programmed temperature vaporizer (PTV) injector were investigated as the interface in on-line supercritical fluid extraction (SFE)-capillary gas chromatography (cGC). The parameters affecting the chromatographic peak shapes as well as the quantitative performance of the interfaces in on-line SFE-cGC were identified and studied. Particular attention was paid to the case where modified extraction fluids were used. Experiments were performed on two different samples. The first sample consisted of PAHs spiked on sand at different concentration levels. The other sample was a polymeric material.     

(Eta3-phenylallyl)(phosphanyloxazoline)palladium complexes: X-ray crystallographic studies,NMR investigations,and Ab initio/DFT calculations

All possible (eta(3)-allyl)palladium complexes (1-4) of the ligand (4S)-[2-(2'-diphenylphosphanyl)phenyl]-4,5-dihydro-4-(2-propyl)-oxazole (L 1) and eta(3)-allyl ligands with one to three phenyl substituents at the terminal allylic centers were synthesized and characterized by X-ray crystal structure analysis and, with respect to allylic isomers, by NMR investigations. Equilibrium geometries, electronic structures, and relative energies of isomeric complexes were computed by restricted Hartree-Fock (RHF) and density functional theory (DFT) calculations; experimentally determined isomer ratios could be reproduced. The results allowed important conclusions to be drawn regarding the mechanism of Pd-catalyzed asymmetric allylic substitutions.     

Synthesis of erythro-alpha-amino beta-hydroxy carboxylic acid esters by diastereoselective photocycloaddition of 5-methoxyoxazoles with aldehydes

A new photoaldol route to alpha-amino-beta-hydroxy carboxylic acid esters is initiated by the photocycloaddition of aromatic or aliphatic aldehydes to 5-methoxyoxazoles. The 4-unsubstituted 5-methyloxazole 1 gave the cycloadducts 8a-f in high yields and excellent exo-diastereoselectivities. Hydrolysis of 8a-f gives the N-acetyl alpha-amino-beta-hydroxy esters 9a-f, which could be subsequently converted into the corresponding Z-didehydro alpha-amino acids 10a-f. Quartenary alpha-amino-beta-hydroxy esters 12, 14, 16, 18, and 20, which are stable against dehydration, were obtained from the 4-alkylated 5-methoxyoxazoles 2-6, in most cases highly erythro-selective due to the high degree of stereocontrol (exo) at the photocycloaddition (to give 11, 13, 15, 17, and 19) level. The relative configurations of the N-acetyl alpha-amino-beta-hydroxy esters were determined by NMR spectroscopy and comparison with chiral pool-derived compounds as well as by X-ray structure determination of the ester 23, formed by hydrolysis of the cycloadduct 22, derived from photocycloaddition of propionaldehyde to the isoleucine-derived oxazole 21.     

On the escape process during phase inversion of an emulsion

This paper deals with a phenomenon which plays an important role in the phase inversion process of emulsions. This process is governed by the interplay of coalescence of droplets, often leading to double emulsions, and the escape of those internal droplets. The latter process retards the inversion process. Coalescence has been the subject of many studies, contrary to the escape event. This paper addresses the escape process both theoretically and experimentally. The model developed analyses the rate of the escape of internal droplets from the mother droplet via a coalescence process, where the internal flow, as generated by the external flow, generates the viscous force for coalescence. Incomplete mixing in the droplet has been assumed. Experimental data on the escape rate of oil droplets from O/W/O emulsions have been analysed using a Computational Fluid Dynamics approach, where the model as indicated above has been incorporated. Experimental data and simulations compare very well. Data have been compared on varying the size of the inner droplets and the rotational speed of the vessel where the double emulsion has been formed and where the escape took place.     

A photochemical route for efficient cyclopeptide formation with a minimum of protection and activation chemistry

An elaborated protocol is described which allows the efficient transformation of di-, tri-, and tetrapeptides into cyclopeptides with a minimum of protection and activation chemistry using the photoinduced electron transfer initiated decarboxylation of N-phthaloyl peptides resulting in C-C coupling between the initially formed carbon radicals.