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Drugs preparative enantioselective resolution

After the first preparation of enantiomerically pure (27 ,2 7 )-t/zreo-methylphenidate hydrochloride (1) in 1958, it is only recently that a great deal of interest has been demonstrated in the synthesis of this molecule. Various approaches to the preparation of enantiomerically pure (2R,2>R)-(-i-)-t/zreo-methylpheni-date hydrochloride (1) are reviewed. These approaches include synthesis using enantiomerically pure precursors obtained by resolution, classical and enzyme-based resolution approaches, enantioselective synthesis approaches, and approaches based on enantioselective synthesis of 2S, 2 Ryerythro-methylphenidate followed by epimerization at the 2-position. Classical resolution approaches have been successfully upscaled to produce 1 on a multi-kilo-gram scale due to the ready availability of racemic ( )-t/zreo-methylphenidate hydrochloride (10). VVfiiIt some enantioselective approaches are short, they do not provide 1 of the desired enantiomeric purity necessary for drug development. Enantioselective synthesis approaches to produce 1, however, will be-... [Pg.13]

The preparation of enantiomerically pure drugs is one factor that makes enantioselective synthesis and the resolution of racemic drugs (separation into pure enantiomers) active areas of research today. [Pg.210]

In recent years, enantioselective chromatography was extended to semipreparative separations and now simulated moving-bed technology (SMB) has become available for the resolution of some synthetic racemates in preparative scale. In the pharmaceutical industry this progress is of considerable interest with respect to enantiopure drug applications. [Pg.696]

The a-amino acids prepared by the synthetic methods just described are racemic unless a resolution step is included, enantiomerically enriched reactants are used, or the reaction is modified so as to become enantioselective. Considerable progress has been made in the last of these methods, allowing chemists to prepare not only L-amino acids, but also their much rarer D-enantiomers. We have already seen one example of this approach in the synthesis of the anti-parkinsonism drug L-dopa by enantioselective hydrogenation (see Section 14.14). A variation of the Strecker synthesis using a chiral catalyst has recently been developed that gives a-amino acids with greater than 99% enantioselectivity. [Pg.1129]

Ibuprofen 128 is another well-known analgesic, anti-inflammatory drug and it is believed that it will be marketed as a single isomer drug. The kinetic enzymatic resolution of racemic ibuprofen has been reported [228]. The reaction for the resolution has been scaled up to make gram quantities of 5-ibuprofen. This was accomplished by two enantioselective reactions each catalyzed by Novozyme 435. In the first reaction, 3(X) g of racemic ibuprofen was esterified with 1-dodecanol to yield the / ester and 5-ibuprofen to produce 89 g of 5-ibuprofen in 85% e.e. In the second reaction, 75 g of the 85% e.e. material was used to prepare 39 g of 5-ibuprofen with a 97.5% e.e. [Pg.118]


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