Trifluoroacetic anhydride → Pitavastatin Impurity 75

Beteiligte Stoffe

Reaktionsschritte

The reaction was terminated by the removal of cells by centrifuging at 4000×g for 20 minutes. The pH of the recovered cell-free supernatant was adjusted to 7.5 using 2M NaOH. MgSO4.1.6H2O (15% w/v based on anhydrous) was dissolved in the cell-free supernatant and the resulting solution was extracted twice with an equal volume of 2-pentanone. The solvent phases were collected and the solvent removed under reduced pressure in a rotary evaporator at 45° C. yielding an orange viscous oil. This was re-dissolved in 50 ml dry, distilled 2-pentanone and again the solvent was removed by rotary evaporation to afford t-butyl 3,5,6-trihydroxyhexanoate (5.08 g, 80% isolated yield). Diastereomeric excess was determined as follows; a sample of t-butyl 3,5,6-trihydroxyhexanoate (30 mg) was derivatised by reaction for at least 10 minutes at room temperature in an excess of trifluoroacetic anhydride, excess anhydride was removed under a stream of dry nitrogen and the residual oil diluted with dichloromethane (1 ml). The sample was analysed using a Chiralcel Dex CB column (25 meter) at a temperature of 140° C. (isothermal). The diastereomers eluted at 14.4 minutes (3R,5S diastereomer) and 15.7 minutes (3S,5S diastereomer). The diastereomeric excess of the sample was found by this method to be 99.7%.

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