RESOLUTION OF DL-PSEUDOEPHEDRINE BY SUPERCRITICAL FLUID EXTRACTION

AIMTo establish a method for resolution of dl-pseudoephedrine by supercritical fluid extraction and to investigate the influence of some parameters upon the resolution process. METHODSUsing single-pass method and HPCE method for determination. RESULTSAs it was demonstrated by the resolution of the racemic pseudoephedrine, CO₂ density and resolving agent can influence the extraction process. Tartaric acid is a good resolving agent, it was shown that a high degree of resolution (100% e.e.) can be achieved within a single extraction step. Dibenzoyl-L-tartaric acid which was ramifications of tartaric acid, showed remarkable partial resolutions, while other resolving agents such as malic acid, phenylalanine, camphorsulfonic acid showed poor partial resolutions at the same condition. In standard experiments, racemic pseudoephedrine was allowed to react with 0.5 equivaient of the chiral agents. Extraction at 0.25, 0.50, 0.75 and 1.0 molar ratios of (2S,3S)-(-)-tartaric acid and dl-pseudoephedrine showed that increase of the molar ratio did not enhance the enantiomeric excess. CONCLUSIONCalculation of molecular force showed that R-acid prefers to react with S-pseudoephedrine. It was comported with experimental results.