The use of heptafluorobutyric acid as a volatile ion-pair reagent in the high-performance liquid chromatographic isolation of SB-223070

The separation of the E-oxime (SB-223070) from the Z-oxime (SB-220582) was achieved using the ion pairing reagent sodium dodecyl sulfonate. When a pur e sample of SB-223070 was required by preparative chromatography from mothe r liquors, modification of the chromatographic conditions was necessary. Th e capacity factor and resolution between the two oximes needed to be increa sed to isolate the E-oxime from the other components in the mother liquor a nd a method to remove the ion-pairing reagent from the isolated product was required. The volatile ion pairing reagent trifluoroacetic acid did not re tain or resolve the components sufficiently but by switching to heptafluoro butyric acid, isolation of SB-223070 was achieved as the heptafluorobutyrat e. This salt was liberated by hydrochloric acid to give the required hydroc hloride salt and the remaining heptafluorobutyric acid was removed by extra ction into dichloromethane. (C) 1998 Elsevier Science B.V. All rights reser ved.