Anomalous dissolution behavior of the diazepam — γ-cyclodextrin complex in polymer solutions

The dissolution process of the diazepam — -cyclodextrin complex in aqueous polymer solutions has been studied. Hydroxypropyl cellulose and polyvinylpyrrolidone stabilize the supersaturated state of the complex, maintaining the higher drug level for a longer period. Polyethyleneglycol and dextran accelerated the dissociation of the complex, and caused a rapid decrease in drug concentration. These anomalous dissolution behaviors are discussed on the basis of viscosity changes of the polymer solutions along with the competitive interaction of polymers for the inclusion complex.     

Photoinduced swelling control of amphiphilic azoaromatic polymer membrane

To control the swelling of polymer membrane by photoirradiation amphiphilic azoaromatic polymer membranes were prepared and a photoinduced change in the swelling degree of water was investigated. The azobenzene moiety in the side chain of the polymer was isomerized from trans form to cis form by ultraviolet (UV) irradiation and reverse isomerization was found by visible light irradiation. The swelling degree of the polymer membrane for water in the dark was decreased by UV radiation, and when visible light irradiation was carried out in the polymer membrane the degree of swelling recovered to the original level. The swelling degree decreased with an increase in the mole fraction of the azobenzene moiety in the dark and under UV irradiation. The deswelling degree of the polymer membrane by UV irradiation also decreased with an increase in the mole fraction of the azobenzene moiety. This reversible change in the swelling degree was considered to be caused by the photoisomerization of the azobenzene moiety in the polymer membrane.     

Direct polycondensation of carbon dioxide with xylylene glycols: a new method for the synthesis of polycarbonates

This communication describes the direct polycondensation of carbon dioxide with p- and m-xylylene glycols using the system trisubstituted phosphine/carbon tetrahalide/base as a condensing agent. The polymerization reaction of carbon dioxide with p-xylylene glycol was carried out in the presence of the condensing agent in N,N-dimethylformamide. The yield was at most 81.0% obtained by using the condensing agent tributylphosphine/carbon tetrabromide/N-cyclohexyl-N′,N′,N″,N″-tetramethylguanidine (CyTMG). The structure of the product was determined by means of ¹H NMR, ¹³C NMR, and IR spectroscopy to be that of a polycarbonate. The molecular weight was estimated to be ca. 1 000–2 000 by ¹H NMR analyses.     

Catalytic Leuckart-Wallach-type reductive amination of ketones

A CpRh(III) complex catalyzes reductive amination of ketones using HCOONH(4) at 50-70 degrees C to give the corresponding primary amines in high yields. The reaction is clean and operationally simple and proceeds at a lower temperature and with higher chemoselectivity than the original Leuckart-Wallach reaction. The new method has been applied to the synthesis of alpha-amino acids directly from alpha-keto acids.     

A new route to 3,4-disubstituted piperidines: formal synthesis of (−)-paroxetine and (+)-femoxetine

A new route to 3,4-disubstituted piperidines was developed using chiral 1,4-dihydropyridines as key intermediates, the synthetic utility of which was demonstrated by formal synthesis of (−)-paroxetine and (+)-femoxetine.     

Development of electrospun poly(vinyl alcohol) fibers immobilizing lipase highly activated by alkyl-silicate for flow-through reactors

Electrospun fibrous membranes composed of poly(vinyl alcohol) (PVA) fibers of approximately 1 μm in diameter, and immobilizing highly activated lipase entrapped in silicate cages with smaller dimensions than the fibers, were developed; and their feasibility as a component of flow-through reactors was studied. The electrospun PVA fibers were prepared from a mixture of PVA solution and a sol obtained from silicon alkoxide(s)—either tetramethoxysilane (TMOS) or dimethyldimethoxysilane (DMDMOS), or both, containing lipase. The fastest initial transesterification rate converting (s)-glycidol to glycidyl n-butyrate with vinyl n-butyrate in batchwise reactions was accomplished by treatment of lipase using the sol obtained from DMDMOS and TMOS together. The values were 4.5-, 21.8-, and 1.8-fold faster than those of systems using lipases that were either non-modified or modified using TMOS alone or DMDMOS alone, respectively. The higher activity of the lipase modified using both DMDMOS and TMOS and immobilized in PVA fibers resulted in a flow-through reactor having a higher degree of conversion at the same retention time compared with that using immobilized non-modified lipase. These results show the feasibility of flow-through reactors composed of electrospun PVA fibers immobilizing lipase highly activated by alkyl-silicate.