Zn -Ion Sensing by Fluorescent Schiff Base Calix[4]arene Macrocycles.

A macrocyclic ligand (H L) containing two o,o'-bis(iminomethyl)phenol and two calix[4]arene head units has been synthesized and its coordination chemistry towards divalent Ni and Zn investigated. The new macrocycle forms complexes of composition [ML] (M=Zn, M=Ni) and [ZnL(py) ], which were characterized by elemental analysis; IR, UV/Vis, and NMR spectroscopy; electrospray ionization mass spectrometry (ESI-MS); and X-ray crystallography (for [ZnL(py) ] and [NiL]). H L allows the sensitive optical detection of Zn among a series of biologically relevant metal ions by a dual fluorescence enhancement/quenching effect in solution.

Endocyclic P-P bond cleavage in carbaborane-substituted 1,2-diphosphetane: a new route to secondary phosphinocarbaboranes.

Carbaborane-substituted 1,2-diphosphetane reacts with elemental lithium and hydrogen chloride to give exclusively secondary mono- and bis(phosphino)carbaboranes. The latter reacts with two equivalents of formaldehyde and one equivalent of aniline to give a carbaborane-substituted 1-aza-3,6-diphosphepane.

Aligned deuterochloroform in cross-linked polystyrene as a new sample for adjusting the magic angle in HR-MAS.

A new and easily usable sample for adjusting the magic angle in a high resolution magic angle spinning (HR-MAS) probe head is a swollen polymer stick in CDCl(3) . The deuterium resonance shows a quadrupolar splitting if the rotor assembly is not at the magic angle, but a sharp singlet if the magic angle is correctly adjusted.

Mechanistic and kinetic insights into the thermally induced rearrangement of alpha-pinene.

The thermal rearrangement of alpha-pinene (1) is interesting from mechanistic as well as kinetic point of view. Carrier gas pyrolyses with 1 and its acyclic isomers ocimene (2) and alloocimene (3) were performed to investigate the thermal network of these hydrocarbons. Kinetic analysis of the major reaction steps allows for a deeper insight in the reaction mechanism.

Thermal isomerization of (+)-cis- and (-)-trans-pinane leading to (-)-beta-citronellene and (+)-isocitronellene.

Catalyzed and uncatalyzed rearrangement reactions of terpenoids play a major role in laboratory and industrial-scale synthesis of fine chemicals. Herein, we present our results on the thermally induced isomerization of pinane (1). Investigation of the thermal behavior of (+)-cis- (1 a) and (-)-trans-pinane (1 b) in a flow-type reactor reveals significant differences in both reactivity and selectivity concerning the formation of (-)-beta-citronellene (2) and (+)-isocitronellene (3) as main products.

Can one gain spectral information plus time by 3D HMBC via back-projection?

The 3D HMBC technique is compared with a time saving technique in which the projection-reconstruction (PR) principle is applied. Using strychnine as an example we demonstrate that after recording essentially three planes of the 3D cuboid a comparable result can be obtained, if certain constraints of the data dimensions are obeyed.

Evidence for the combined participation of a C10 and a C15 precursor in the biosynthesis of moenocinol, the lipid part of the moenomycin antibiotics.

Upon feeding of [2-(13)C,4-(2)H]-1-deoxy-D-xylulose to Streptomyces ghanaensis, the deuterium label was retained exclusively at positions C-7 and C-17 in the moenocinol part of the moenomycin antibiotics. This result vindicates the hypothesis that the C(25) structure of moenocinol is assembled from a C(10) and a C(15) precursor, each of which requires for its formation the involvement of a dimethylallyl diphosphate starter unit.

Studies on the interaction of the antibiotic moenomycin A with the enzyme penicillin-binding protein 1b.

The interaction of a moenomycin derivative with the enzyme penicillin binding protein 1b (PBP 1b) has been studied by means of STD NMR. The results obtained initiated the synthesis of a number of moenomycin derivatives modified in unit A including a moenomycin-ampicillin conjugate and determination of their antibiotic activities. A protocol is described that allows studying the interaction of moenomycin analogues with PBP 1b by fluorescence correlation spectroscopy.

Tandem Protocol for the Stereoselective Synthesis of Different Polyfunctional beta-Amino Acids and 3-Amino-Substituted Carbohydrates.

Conjugate addition of homochiral amidocuprates or lithium amides based on (R)-N-(1-phenylethyl)(trimethylsilyl)amine to alpha,beta-unsaturated esters proceeds stereoselectively and allows the synthesis of beta-amino acids. Trapping of the intermediate ester enolate with D(2)O affords the corresponding deuterated compounds. anti-alpha-Alkyl-beta-amino acids are obtained stereoselectively after transmetalation of the lithium/copper ester enolate to the titanium ester enolate and trapping with carbon electrophiles.