Book review

Communicated by Professor Zimmermann     

Synthese des Makrolid-Antibiotikums (−)-A26771B mit Photolactonisierung als Schlüsselreaktion und Computersimulation als effektive Optimierungshilfe

Synthesis of the Macrolide Antibiotic (?)-A2677IB Using Photolactonization as a Key Reaction and Computer Simulation as an Effective Aid in Optimization The title compound has been synthesized in a sequence of 21 steps starting from phenol. The cyclic skeleton has been built up in the earlier part of the synthesis by photolactonization. This reaction supplies C(6), with a functionality, not present in the target structure, but useful for oxygenation at C(4) and generation of the stereogenic center C(5). The Barton/McCombie reaction provides a product deoxygenated at C(6), but only after an adjacent oxirane ring has been opened at the cost of an increase in the number of overall steps. X-Ray structural information and computational modelling of appropriate molecules proved to be essential to selection of optimal conditions for various transformations.     

Über die Struktur von Imidazolin- und Imidazolidin-Derivaten aus 2-Amino-2-desoxy-hexosen

In earlier publications [1] [2] [3] [4] a pyranoid structure has been proposed for the sugar moiety of imidazoline and imidazolidine derivatives from D -glucosamine. But by NMR.-spectra and periodate oxidation the sugar moiety of these compounds and of similar derivatives from other 2-amino-2-deoxy-sugars is now shown to be of furanoid structure.     

Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions

Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus c_sol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation.     

Formeln für Pole der Resolvente und den Radius eines wesentlichen Spektrums

Let E be a complex Banach space and T a bounded linear operator. If _w(T) is the set of all spectral points of T which are not poles of the resolvent and r_w(T) its radius, we give formulas for the moduli of all poles lying outside the circle with radius r_w(T). We further prove that , where (T)=inf(T–FF(T–F)=(T–F)F=0,FF and F is the Caradus class of operators with rational resolvent. Finally we give an estimation of r_w(S+T) and r_w(S·T).     

Performance of slotted pores in particle manufacture using rotating membrane emulsification

This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.