A chiral crown ether Is successfully used as a pseudo stationary phase In capillary zone electrophoresis to separate optically active amines. On the basis of the results obtained from the separation of more than 20 amines, two recognition mechanisms are proposed: (I) the four crown ether substituents act as chiral barriers for the guest molecules and (II) lateral electrostatic Interactions occur between host and guest. These results are confirmed by thermodynamic studies on the hostguest complexes. Best resolutions are achieved If the chiral center Is adjacent to the amine functionality. However, even racemates with a chiral center In the ^-position to the amine could be resolved excellently. For the separation of aliphatic amino acids a method has been developed allowing detection by an Indirect detection mode.

Marked for life. For the characterization of larger proteins new NMR spectroscopy methods that focus on side‐chain methyl groups have been developed by using selectively isotope‐labeled precursor compounds. Here we report on the synthesis of a 13C‐methyl‐group‐labeled methionine precursor on a preparative scale, and its incorporation into the SH2 domain of the protein PLC‐γ1 (see scheme).

More than six decades after proposing copper acetylide, Cu2C2, as catalytically active species in ethynylation reactions by Walter Reppe, the explosive species have been experimentally identified and investigated during catalysis in detail now. Taking into account specific safety precautions, unequivocal qualitative characterization was achieved by Raman spectroscopy and X‐ray powder diffraction of supported copper catalysts Cu/Bi/SiO2 during and after activation and catalysis in comparison to bulk Cu2C2 materials. Quantification of Cu2C2 succeeded by thermal analysis and Raman spectroscopy. Its formation in aqueous suspension is studied starting from copper(II) oxide catalysts including dissolution, reduction and precipitation steps. Copper acetylide formation can be correlated with catalytic performance in the ethynylation of formaldehyde to 1,4‐butynediol.

Conventional fossil fuels such as gasoline or diesel should be substituted in the future by environmentally-friendly alternatives in order to reduce emissions in the transport sector and thus mitigate global warming. In this regard, iso-butanol is very promising as its chemical and physical properties are very similar to those of gasoline. Therefore, ongoing research deals with the development of catalytically-supported synthesis routes to iso-butanol, starting from renewably-generated methanol. This research has already revealed that the dehydrogenation of ethanol plays an important role in the reaction sequence from methanol to iso-butanol. To improve the fundamental understanding of the ethanol dehydrogenation step, the Temporal Analysis of Products (TAP) methodology was applied to illuminate that the catalysts used, Pt/C, Ir/C and Cu/C, are very active in ethanol adsorption. H2 and acetaldehyde are formed on the catalyst surfaces, with the latter quickly decomposing into CO and CH4 under the given reaction conditions. Based on the TAP results, this paper proposes a reaction scheme for ethanol dehydrogenation and acetaldehyde decomposition on the respective catalysts. The samples are characterized by means of N2 sorption and Scanning Transmission Electron Microscopy (STEM).

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81 in 67% yield. For this purpose, Boc-trans-3-@-cyanome-thy1phenoxy)proline was hydrogenated to the p-aminome-thy1 compound and acylated with the benzyloxycarbonyl protected S-prolinehydroxysuccinimide ester to the diastereomeric dipeptides (7a) and (76) (yield loo%, relative to the Boc-compound). The diastereomers could not be separated Angew Chem Int. Ed Engl 20 (1981) No. 3 0 Verlag Chemie, GmbH, 6940 Weinhem, 1981 0S70-0833/81/0303-0281 $ 02.50/0[5] Dihydrozizyphin G prepared from zizypbin has a value of [u\h"= -67" (J.

A number of mesoionic 2-alkylthiothiazol-4-ones (6) were prepared by alkylation of rhodanines or by the reaction of a-bromomalonates with dithiocarbamates. The photolysis of these mesoionic compounds proceeds via a highly strained, bicyclic, ring contraction product which rearranges to a thiazolin-2-one (1 4). loses sulphur, affording a p-aminoacrylate (1 l ) , or is trapped by methanol giving methoxy-p-lactams (1 2) and (1 3). THE photochemistry of certain classes of five-membered mesoionic heterocycle has been generally rationalized in terms of a mechanism which involves a transient fourmembered carbonyl-containing ring 1, formed by photolytically induced ring contraction (Scheme 1). This process presents an attractive possibility for p-lactam synthesis from mesoionic thiazolones, imidazolones, or oxazolones.New syntheses of p-lactams are always designed with a view to their application in the synthesis of penicillins and cephalosporins. This requires a polyfunctional precursor. Accordingly the known 2-alkylthiothiazolium-4-olates (Scheme 2), having the alkylthio-group in the desired position, were considered to be good models for a photolytically induced cephalosporin or penicillin synthesis.The appropriate substituent on C-5 of the mesoion would be an amido-group. However, all attempts up to now to prepare amido-substituted mesoionic thiazolones of type (6) have failed.Since the conversion of carboxy-p-lactams into aminop-lactams has been de~cribed,~ another useful substituent in position 5 would be a carboxy-group. We were, in

Eingegangen a m 18. Januar 1983Versuche zur Synthcse des 3-Oxoesters 5 aus N-Boc-3-Hydroxyprolin (1) werden beschrieben. Acylierung von Meldrumsaure (2,2-Dinlethyl-l,3-dioxan-4,6-dion) mit dem Pyrrolidin-2,3-carbolacton 8 in Cegenwart von 4-(Dimethylamino)pyridin liefert die Acylmeldrumsaure 7, die thermisch zum 4-Hydroxy-2-pyron 9 cyclisiert wird. Reduktion von 9 mit Amin-Boran-Komplexen im schwach Sauren fuhrt zu den isomeren Synthesis of ruc-DetoxinineAttempts to synthesize the 3-0x0 ester 5 starting with N-Hoc-3-hydroxyproline (1) are described. Acylation of Meldrum's acid (2,2-dimethyl-l,3-dioxane-4,6-dione) by the pyrrolidine-2,3-carbolactone 8 in the presence of 4-(dimethylamino)pyridine affords the acyl derivative 7 of Meldrum's acid which on heating cyclizes to give the 4-hydroxy-2-pyrone 9. Reduction of 9 with amineborane complexes in weakly acidic medium leads to the hydroxypyrone isomers 10 and 11; analogous reaction with 16 produces 17 and 18 (isomeric ratio about 1 : 2). After cleavage of the Boc rest 10 and 11 undergo opening of their lactone rings yiclding the title amino acid 19 and its isomer 20, respectively. Under identical conditions 21 is opened to yield the unsaturated amino acid 22.4-Amino-3-hydroxycarbonsauren wurden in der Natur vereinzelt aufgefunden. Sie stellen Baustcine von biologisch aktiven Peptiden dar'). Die Titelverbindung Detoxinin (19) ist Teil des Depsipeptids Detoxin, das gegenuber dern Nucleosidantibiotikurn Blasticidin S selektive antagonistische Wirkung zeigt2a).Obgleich vor kurzem 6-Detoxininlactone -zwecks Festlegung der absoluten Konfiguration -durch Anellierung des Pyrrolidinrings an entsprechende epirnere Hexopyranosen uber zahlreiche Schritte synthetisiert wurdenZb ), ist die Aminosaure Detoxinin selbst noch nicht beschrieben. Der leichte Zugang zu cis-3-Hydroxyprolin aus Prolinl) legte Versuche nahe, dieses zum Ausgangspunkt einer Detoxininsynthese zu machen. Sie lauft irn wesentlichen auf eine Verlangerung der Carboxylgruppe des 3-Hydroxyprolins zur P-Hydroxycarbonsaurefunktion hinaus. Von den in der Literatur beschriebenen" Synthesewegen fur eine entsprechende Umwandlung konnte die Acylacetatbildung rnit nachtraglicher Reduktion der b-Oxogruppe erfolgreich durchgefiihrt werden. Die Synthese gestattete den vorteilhaften Einbau der 3-Hydroxygruppe des Prolins in ein konfigurationsstabiles cis-5,6-iiberbrucktes 4-Hydroxy-2-pyron. Reduk-