Adapted from biocatalytic reactions the principle of the membrane reactor (represented schematically on the right) is applicable to the continuous asymmetric addition of diethylzinc to benzaldehyde. α,α-Diphenyl-L-prolinol is coupled to a homogeneously soluble polymer (1), which enables it to be retained in the reaction vessel by an ultrafiltration membrane. By decoupling the residence time of reactants and the catalyst the total turnover number could be increased by a factor of 10.
α,α-Diphenyl-L-prolinol, when coupled to a polymer soluble in organic solvents, gives surprising results for the addition of diethylzinc to aldehydes. For benzaldehyde, the enantiomeric excess strongly depends on the initial substrate ratio: an excess of diethylzinc yields (S)-1-phenylpropanol with up to 80% ee, while an excess of benzaldehyde leads to the (R)-1-phenylpropanol with up to 50% ee. The kinetic properties of the catalyst and the results with other aldehydes are also described. The polymer 1 is a copolymer of octadecyl methacrylate and 2-hydroxyethyl methacrylate.
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Enantiomerically pure C-2-symmetric 1,4-diols embodying bicyclic C-frameworks were synthesized by means of asymmetric carbo-Diels-Alder reactions as key steps (Scheme 1). They were investigated as chiral ligands in the enantioselective addition of ZnEt(2) to aromatic aldehydes. In the presence of 20-40 mol-% of the titanates formed from these diols and [Ti(i-PrO)(4)] at -78 degrees, the respective 1-arylpropanols were obtained with enantiomer ratios up to 93:7(Scheme 2, Table).
The improvement of SiranR openpored glass carriers by chemical modification makes it possible to immobilize both anchorage dependent and suspension cells in high cell density. This property makes an operation in fixed and fluidized bed systems possible. Different chemically modified sinter glass carriers have been synthesized. For their usefulness in cell culture technology they have been tested with an anchorage dependent celline and a suspension celline (CHO K1, Mouse-Mouse-Hybridoma). These screening experiments were performed in shaker flasks. Carrier samples for cell counts have been taken periodically. Modification of sinter glass with proteins of the "extracellular matrix" promotes cell attachment and cell growth in comparison with the unmodified sinter glass control. After a few days during the experiment with the anchorage dependent celline a serumfree media could be used. The Hybridoma celline has been cultured serumfree showing an interesting growing pattern. In this kind of experiments CHO K1 attached and spreaded over the surface forming cell aggregates, whereas the Hybridomas populated the porous structure. Modification of SiranR glass carriers using silanization reagents will give a well defined surface which is stable against hydrolysis. This defined derivatized matrix surfaces will make further studies on cell attachment, cell physiology and product expression possible. KEYWORDS Mammalian Cell Culture, Siran Carrier, Immobilization
