Semi-preparative scale

In the case of the (1 )-configured olefinic ketones high conversion rates and enantiomeric excesses were achieved on the analytical and on the semi-preparative scale. With TBADH, which requires a slightly higher reaction temperature, decomposition of the halogenated substrates was observed. In the case of CPCR, which was used as a partially purified enzyme preparation from the parental strain, the formation of up to 50% of the fully saturated alcohols was observed (Scheme 2.2.7.18). Substrate (l )-33 could be converted into enantiopure (S)- and (R)- E)-32, respectively, by recLBADH- and HLADH/CPCR-catalyzed reaction. 

Figure 4. Semi-preparative-scale separation of 2,2-dimethyl-3-phenyloxirane on Mn-CAM2 (Schurig et ah, 1990).

Figure 7. Semi-preparative-scale separation of the invertomers of l-chloro-2,2-dimethylaziridine by complexation GC on Ni-CAMj at 22°C and 1.5 bar N2 in 3 h at 22°C. Injected amount of racemate 6 fi (further experimental conditions cf. text). The (S)-enantiomer is eluted before the (it)-enantiomer on Ni-CAMj (Schurig and Leyrer, 1990).

Figure 11. Semi-preparative-scale stereoisomeric separation of 1.6-dioxaspiro[4.4]nonanes on Ni-CAR2 (experimental conditions cf. text) (Schurig, 1987).

Underivatized ( )-tunichrome An-1 was synthesized recently on a semi-preparative scale 163). Its availability will help to clarify the biological role of tunichromes, including their interactions with vanadium. 

P. Schmitt-Kopplin, Capillary Electrophoresis Methods and Protocols, Humana, 2007, ISBN 9781588295392 J.P. Landers, Handbook of Capillary Microchip Electrophoresis and Associated Microtechniques, CRC Press, Boca Raton, Florida, 2007, ISBN 9780849333293, C. Henry, Microchip Capillary Electrophoresis, Humana, 2006, ISBN 9781588292933.] The bands are eluted according to their isoelectric points. Isoelectric focusing standards are available which can be used in a preliminary run in order to calibrate the effluent from the column, or alternatively the pH of the effluent is recorded using a glass electrode designed for the purpose. Several efficient commercial equipment are available for separating proteins on a preparative and semi-preparative scale. 

It must also be noted that the anthocyanin and the flavanol conq ete in the different steps of the reaction. Nevertheless, and due to the low proportion of the hydrated form of the anthocyanin at the pH value of the reaction medium (2.2) which considerably decreases its ability to act as a nucleophile, this competition is in favor of the flavanol which is predominantly attacked first. This was shown by detection by LC/ESI-MS of the flavanol intermediate at m/z 333 amu in the negative ion mode, while the corresponding anthocyanin intermediate was not detected. Isolation of the flavanol intermediate was achieved through HPLC at the semi-preparative scale and further reaction with malvidin 3-0-glucoside was shown to afford the two ethyl-bridged anthocyanin-flavanol adducts. 

Various dermatan sulfate derived di-, tetra-, hexa-, octa-, deca- and dodeca-saccharide mixtures have been prepared and purified (on a semi-preparative scale) by controlled depolymerization of dermatan sulfate using chondroitin ABC lyase, The pathways of InsPe hydrolysis by phytase from wheat bran of Triticum aestivum have recently been established. ... 

Inherent in all RPC and HlC investigations with peptides or proteins is the question of the end use to which the separated products will be applied. If the task involves purification solely for subsequent primary structure determination (i.e., essentially an analytical task at a semi-preparative scale), then control over preservation of bioactivity may not be necessarily relevant. Obviously, with a new or partially characterized protein, recovery of the component of interest with high mass and bioactivity balance is essential. For preparative methods where subsequent biological uses are contemplated, it is similarly mandatory that the design of the RPC or HlC separation system specifically address recovery issues. High recovery of bioactivity can usually be satisfied without sacrificing the obvious demands of selectivity through proper attention to the physicochemical consequences of the dynamic behavior of the polypeptide or protein of interest in bulk solution and at liquid-solid interfaces. 

Optical resolution of the key intermediates, trans 41 and cis 4 2, was achieved, with base-line resolution, by chiral column chromatography on a chindpak AS column, to afford (-)-trans 41, (+)-inns 41, (-)-cis 42, and (+)-c 42 on a semi-preparative scale. The first total syntheses of (-)-6,7-secoagroclavine 47] and its (+>enantionier [(+)-/ranr 4 7] were completed in a one-pot operation by the reaction of (-)- and (+)-trans 41 with an excess of methylmagnesium iodide, respectively, followed by reduction of the resulting methylhydroxykunines [(-)- and (+)-tnms 49], with zinc in metiianolk hydrochloric acid. 

Liquid-liquid chromatography has developed into HPLC, which is discussed in Chapter 7. Most HPLC separations can be modified to the preparative or semi-preparative scale. This is a major undertaking for the new practitioner and is beyond the scope of this volume. 

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