Die Methoden zur direkten Messung des osmotischen Drucks

Ohne Zusammenfassung     

A new ring transformation of 3-halo-2-azidopyridine 1-oxides. A novel synthesis of 1,2-oxazin-6-ones

The course of the thermal ring-opening and recyclization of 2-azidopyridine 1-oxides is radically altered by the presence of a 3-halo substituent. Provided the 6-position is blocked, recyclization leads to a 6-cyano-6-halo-1,2-oxazine which hydrolyzes very readily to the 6H-1,2-oxazin-6-one. The structure of 4-bromo-3-methyl-6H-1,2-oxazin-6-one so obtained was confirmed by single crystal X-ray analysis. If the 6-position is not blocked, the product undergoes a further ring opening to give (Z)-β-cyanoacrylates.     

Molecular tubes for lipid sensing: tube conformations control analyte selectivity and fluorescent response

Two fluorescent sensors for lipids have been prepared and tested for detection of a number of hydrophobic compounds of varying shape and size. The data suggest that the two sensors have a different mode of fluorescent response. Yet, the two sensors are only different in the bridging group--one having a flexible amide and one having a rigid allyl bridge. The fluorescence data are explained based on a difference in conformation of the two sensors in aqueous solution.     

Pyoluteorin derivatives. II. Synthetic approaches to pyrrole ring substituted pyoluteorins

A method for the regiospecific synthesis of 3-substituted 2-aroylpyrroles is described. These pyrroles, which are structurally related to the naturally occurring antibiotic pyoluteorin, are prepared by a Friedel-Crafts aroylation of 4-substituted pyrrole-3-carboxylic acid esters with 2,6-dimethoxybenzoyl chloride. The carboalkoxy group is then removed by hydrolysis and decarboxylation to produce isomerically pure 3-substituted-2-(2′,6′-dimethoxybenzoyl)pyrroles ( 5 and 13 ). Conversion of these pyrroles into pyoluteorin-like compounds led to some unexpected products which arise from facile cleavage of the dihydroxybenzoyl portion of the molecules during chlorination.     

A practical synthesis of pyoluteorin

A convenient, large-scale synthesis of the antibiotic pyoluteorin, 2,3-dichloro-5-(2′,6′-dihydroxybenzoyl)-pyrrole ( 1 ), is described. A key step in the synthesis involved a Friedel-Crafts aroylation of pyrrole with 2,6-dimethoxybenzoyl chloride ( 3 ) in methylene chloride. The desired intermediate, 2-(2′,6′-dimethoxybenzoyl)pyrrole ( 4 ), was obtained as the major product, along with a product of beta substitution ( 6 ). Compound 4 was converted to pyoluteroin ( 1 ) in four steps in an overall yield of 51%.     

Transition metal catalysed ammonia-borane dehydrogenation in ionic liquids

Significant advantages result from combining the disparate hydrogen release pathways for ammonia-borane (AB) dehydrogenation using ionic liquids (ILs) and transition metal catalysts. With the RuCl(2)(PMe(3))(4) catalyst precursor, AB dehydrogenation selectivity and extent are maximized in an IL with a moderately coordinating ethylsulfate anion.     

Benchmarking green chemistry adoption by the Indian pharmaceutical supply chain

This paper provides the first benchmarking study of green chemistry (GC) adoption by the Indian pharmaceutical supply chain based on information from industry representatives leading such efforts. Results demonstrate that generic drug pharma and Active Pharmaceutical Ingredients (API) manufacturers in India exhibit significant interest and some advances in using GC principles. At the same time, majority (65%) of Indian companies rely on treatment and disposal of waste water instead of source reduction and one in five (20%) does not use any GC metrics. The study found that generic pharma is more advanced in adopting GC principles than API manufacturers. Regulatory risk and time pressures to deliver drugs were reported as the two most significant barriers for greater adoption of GC in India, while cost savings and environmental regulations were cited as the top two drivers. The paper concludes with some recommendations for advancing GC adoption in India.     

Synthesis of 3,5- and 3,6-linked calix[n]naphthalenes

The preparation of calix[n]naphthalenes from derivatives of 2,7-dihydroxynaphthalene is described. 1,8-Dialkyl substitution is used to direct the regiochemistry of the acid-catalyzed condensation reactions. Acyclic peri substituents lead to a 3,5-linked calix[3]naphthalene, whereas cyclic peri substituents give predominantly a calix[5]naphthalene with the corresponding 3,6-linkage. The 3,6-linked calix[4]naphthalene is prepared in pure form by a dimerization strategy.     

Shape-selective sensing of lipids in aqueous solution by a designed fluorescent molecular tube

The design, synthesis, and recognition properties of two isomeric calixnaphthalene-type molecular tubes is described. The anti isomer showed strong fluorescence quenching upon titration with various simple lipid guests in water, in which the more hydrophobic guests associated with higher affinity. The syn isomer bound long straight-chain guests tightly with a similar fluorescence-quenching response. However, the syn isomer was more selective, giving an increase in fluorescence upon titration of guests which could not thread through the tube. Thus, the syn isomer is a selective fluorescent sensor for long straight-chain lipids.