Oxygen-17 nuclear magnetic resonance: The effects of remote unsaturation on 17o-chemical shifts in polycyclic ethers

Natural-abundance ¹⁷O-NMR spectra of 7-oxanorbornane exo-3-oxatricyclo [3.2.1.0^2.4]octane and their unsaturated derivatives (endo cyclic and exocyclic double bonds) have been measured. Linear correlation laws were observed for $\text{δ}{}_{\mathrm{o}}\text{δ}{}_{\mathrm{c}}$ of these ethers/corresponding hydrocarbons. The “cyclization shifts” for δ_o in ethers were not correlated by the “cyclization shifts” for δ_c of the corresponding hydrocarbons.     

Dipolmomente 1, 6-überbrückter [10]- Annulene

The dipole moments of 1, 6-bridged [10]-annulenes of type I (X = CH₂, O, NH) and of bromo derivatives with X = CH₂, O are in agreement with the previously established structure of these compounds if a partial moment of approximately 0,8 D is assigned to the non-planar π-electron system.     

Regioselective rearrangement of 7-azabicyclo[2.2.1]hept-2-aminyl radicals: first synthesis of 2,8-diazabicyclo[3.2.1]oct-2-enes and their conversion into 5-(2-aminoethyl)-2,3,4-trihydroxypyrrolidines, new inhibitors of α-mannosidases

Enantiomerically pure 2,8-diazabicyclo[3.2.1]oct-2-ene derivatives (+)-5 and (−)-5 have been obtained from 2-azido-3-tosyl-7-azabicyclo[2.2.1]heptanes (+)-1 and (−)-2 and their enantiomers, by ring expansion under radical conditions. Compounds (+)-5 and (−)-5 were transformed into hemiaminals 9 ((3S,4R,5R)- and 10 ((3R,4S,5S)-5-(2-aminoethyl)-2,3,4-trihydroxypyrrolidine) that are good inhibitors of α-mannosidases.     

The rhodium complex of a tris(bipyridine) ligand—Its electrochemical behaviour and function as mediator for the regeneration of NADH from NAD+

The tris-bipyridine ligand3a and its stoichiometric Rh³⁺ complex have been prepared. Cyclovoltammograms of the complex at pH 7.4 using a glassy carbon disk electrode reveal a strong reduction peak at –620 mV and two weak reduction peaks at more negative voltage. The reduction potential of the new complex is shifted by 300 mV to more positive values as compared to [Rh(bipy)₃]³⁺. There is no reversible reoxidation peak of the Rh(I) complex formed due to the decomplexation of one of the three bipyridine units in the course of the transition Rh(III)Rh(I). The Rh(III) complex of3a was also studied with respect to its function as a possible redox mediator for the electrochemical regeneration of NADH from NAD⁺. The preparative electrolysis of the Rh³⁺ complex of3a in the presence of NAD⁺ yields a selective formation of NADH, whereas NAD dimers were not detected. On the other hand, a significant acceleration of this reaction compared to [Rh(bipy)₃]³⁺ was not observed.     

Synthesis, Characterization, and Electrochemistry of sigma-Bonded Cobalt Corroles in High Oxidation States

The synthesis, electrochemistry, spectroscopy, and structural characterization of two high-valent phenyl sigma-bonded cobalt corroles containing a central cobalt ion in formal +IV and +V oxidation states is presented. The characterized compounds are represented as phenyl sigma-bonded cobalt corroles, (OEC)Co(C(6)H(5)) and [(OEC)Co(C(6)H(5))]ClO(4), where OEC is the trianion of 2,3,7,8,12,13,17,18-octaethylcorrole. The electronic distribution in both molecules is discussed in terms of their NMR and EPR spectroscopic data, magnetic susceptibility, and electrochemistry.     

Investigation of excess enthalpies of selected binary and ternary solutions and mixtures

The excess enthalpies were investigated for 12 binary and 4 ternary systems, including mixtures and solutions of electrolytes and non-electrolytes. The excess enthalpies of mixtures and integral heats of solutions were measured with an isoperibol calorimeter at 35 °C. Heats of fusion and heat capacities as functions of temperature were measured with a Perkin Elmer Corp., DSC-2. Integral heats, heats of fusion and heat capacities allow investigations of excess enthalpies of solutions. For modelling of the experimental results, the modified Redlich-Kister equation was used with good success.

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Zusammenfassung Für 12 binäre und temäre Systeme, darunter Mischungen und Lösungen von Elektrolyten und Nichtelektrolyten, wurden die Exzessenthalpien untersucht. Die Exzessenthalpien der Mischungen und die integralen Lösungsenthalpien wurden mit einem isoperibolen Kalorimeter bei 35 °C gemessen. Die Schmelzwärmen und spezifischen Wärmekapazitäten in Abhängigkeit von der Temperatur wurden mit einem DSC 2 der Fa. Perkin-Elmer bestimmt. Die integralen Wärmen, Schmelzwärmen und Wärmekapazitäten erlauben, die Exzessenthalpien der Lösungen zu untersuchen. Die Versuchsergebnisse lassen sich erfolgreich mit modifizierten Redlich-Kister-Gleichungen modellieren.

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12 4 , . 35° . -2 - . , . -.

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The author expresses his gratitude to the leader of the Teaching and Research TEAM, Prof. Dr. H. Schuberth, and to Dr. G. Figurski, for help and discussions.     

Synthesis of benzazepines and their rearrangement to quinolines and pyrrolo(2,3-b) quinolines

BECKMANN or SCHMIDT rearrangement of ethyl trans-4-oxo-1-phenyl-2-tetralincarboxylate ( 2 ) affords ethyl trans-2,3,4,5-tetrahydro-2-oxo-5-phenyl-1H-benzo [b] azepine-4-carboxylate ( 4 ). Mild treatment of trans-2,3,4,5-tetrahydro-1-methyl-2-oxo-5-phenyl-1 H-benzo-[b] azepine-4-carboxylic acid ( 7 ) with thionyl chloride and pyridine in dimethylformamide and subsequent reaction with an amine yields the corresponding benzazepine-4-carboxamide. If he it is applied during the preparation of the acid chloride, rearrangement occurs yielding cis and trans derivatives of hydrocarbostyril. 2,3,4,5-Tetrahydro-1,4-methano-1-methyl-5-phenyl-1 H-benzo-[b] azepinium chloride ( 25 ) reacts with primary or secondary amines to cis-tetrahydroquinoline derivatives. When heated above its melting point, trans-4,5-dihydro-2-methylamino-5-phenyl-3H-benzo-[b] azepine-4-carboxylic acid ( 29 ) rearranges with elimination of water to a mixture of cis-and trans-2,3,3a,4-tetrahydro-1-methyl-2-oxo-4-phenyl-1H-pyrrolo [2,3-b] quinoline ( 32 and 31 ). The reduction of 31 was investigated. The mechanisms of the rearrangements are discussed.     

The C-disaccharide alpha-C(1-->3)-mannopyranoside of N-acetylgalactosamine is an inhibitor of glycohydrolases and of human alpha-1,3-fucosyltransferase VI. Its epimer alpha-(1-->3)-mannopyranoside of N-acetyltalosamine is not

The radical C-glycosidation of (-)-(1S,4R,5R, 6R)-6-endo-chloro-3-methylidene-5-exo-(phenylseleno)-7-ox abi cyclo[2. 2.1]heptan-2-one ((-)-4) with 2,3,4, 6-tetra-O-acetyl-alpha-D-mannopyranosyl bromide gave (+)-(1S,3R,4R, 5R,6R)-6-endo-chloro-5-exo-(phenylseleno)-3-endo-(1',3',4', 5'-tetra-O-acetyl-2', 6'-anhydro-7'-deoxy-D-glycero-D-manno-heptitol-7'-C-yl)-7-oxabi cyc lo[ 2.2.1]hept-2-one ((+)-5) that was converted into (+)-(1R,2S,5R, 6R)-5-acetamido-3-chloro-2-hydroxy-6-(1',3',4',5'-tetra-O-acetyl)-2', 6'-anhydro-7'-deoxy-D-glycero-D-manno-heptitol-7'-C-yl)cyclohex -3-en- 1-yl acetate ((+)-10) and into (+)-(1R,2S,5R, 6S)-5-bromo-3-chloro-2-hydroxy-6-(1',3',4',5'-tetra-O-acetyl-2', 6'-anhydro-7'-deoxy-D-glycero-D-manno-heptitol-7'-C-yl)cyclohex -3-en- 1-yl acetate ((+)-19). Ozonolysis of (+)-10 and further transformations provided 2-acetamido-2,3-dideoxy-3-C-(2', 6'-anhydro-7'-deoxy-D-glycero-D-manno-heptitol-7'-C-yl)-D-galac tos e (alpha-C(1-->3)-D-mannopyranoside of N-acetylgalactosamine (alpha-D-Manp-(1-->3)CH(2)-D-GalNAc): 1). Displacement of the bromide (+)-19 with NaN(3) in DMF provided the corresponding azide ((-)-20) following a S(N)2 mechanism. Ozonolysis of (-)-20 and further transformations led to 2-acetamido-2,3-dideoxy-3-C-(2', 6'-anhydro-7'-deoxy-D-glycero-D-manno-heptitol-7'-C-yl)-D-talose (alpha-C(1-->3)-D-mannopyranoside of N-acetyl D-talosamine (alpha-D-Manp-(1-->3)CH(2)-D-TalNAc): 2). The neutral C-disaccharide 1 inhibits several glycosidases (e.g., beta-galactosidase from jack bean with K(i) = 7.5 microM, alpha-L-fucosidase from human placenta with K(i) = 28 microM, beta-glucosidase from Caldocellum saccharolyticum with K(i) = 18 microM) and human alpha-1, 3-fucosyltransferase VI (Fuc-TVI) with K(i) = 120 microM whereas it 2-epimer 2 does not. Double reciprocal analysis showed that the inhibition of Fuc-TVI by 1 displays a mixed pattern with respect to both the donor sugar GDP-fucose and the acceptor LacNAc with K(i) of 123 and 128 microM, respectively.     

Laser-induced fluorescence detection schemes for the analysis of proteins and peptides using capillary electrophoresis

Over the past few years, a large number of studies have been prepared that describe the analysis of peptides and proteins using capillary electrophoresis (CE) and laser-induced fluorescence (LIF). These studies have focused on two general goals: (i) development of automatic, selective and quick separation and detection of mixtures of peptides or proteins; (ii) generation of new methods of quantitation for very low concentrations (nm and subnanomolar) of peptides. These two goals are attained with the use of covalent labelling reactions using a variety of dyes that can be readily excited by the radiation from a commonly available laser or via the use of noncovalent labelling (immunoassay using a labelled antibody or antigen or noncovalent dye interactions). In this review article, we summarize the works which were performed for protein and peptide analysis via CE-LIF.