Ibuprofen belongs to the non-steroidal anti-inflammatory drug (NSAID) family known as profens. Studies demonstrate that (S-ibuprofen is 160 times more potent than (R-ibuprofen in vitro, while the accumulation of (R-ibuprofen can cause serious side effects such as gastrointestinal pain. Candida rugosa lipase was used to enantioselectively esterify racemic ibuprofen with decan-1-ol and butan-1-ol in cyclohexane with an enantiomeric ratio (E) of 130 and 46, respectively, in up to 46% conversion. Separation by bulb-to-bulb distillation of (R)-ibuprofen and unreacted alcohol from the corresponding (S)-alkyl ibuprofen ester was possible for the decyl but not the butyl case. The enantioselective hydrolysis of (S)-alkyl ibuprofen esters with the same biocatalyst in aqueous phosphate buffer was twice as slow for the decyl alcohol versus the butyl example. The combined environmentally friendly enantioselective esterification and hydrolysis of ibuprofen insured the isolation of (S)-ibuprofen with a greater than 99% enantiomeric excess.
Two efficient chiral auxiliary mediated asymmetric syntheses of synthetically useful l-acyl-2-alkyl-1,2-dihydropyridines are described.For many years there has been considerable interest in the synthesis, synthetic utility, and biological activity of various dihydropyridines.1 The ability of an iV-acyl substituent to stabilize2 the dihydropyridine system has encouraged the use and study of 1-acyldihydropyridines as synthetic intermediates. Several 2-unsubstituted 1-(alkoxycarbonyl)-l,2-dihydropyridines 1 have proven to be useful dienes for the Diels-Alder reaction and have been Supplementary Material Available: Experimental details for the preparation of 7a and 21a and physical data for 7,15, and 21a,b (13 pages). This material is contained in many libraries on microfiche, immediately follows this article in the microfilm version of the journal, and can be ordered from the ACS; see any current masthead page for ordering information.
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