| abstract |
The invention provides a method for selectively extracting a compound of formula I: <IMAGE> Formula I wherein: R is hydrogen or -NR3R4; and when R=-NR3R4, R3 and R4 may be the same or different and are selected from hydrogen and straight or branched (C1-C4)alkyl; R1 and R2 may be the same or different and are selected from straight or branched (C1-C6)alkyl; from an aqueous mixture containing a compound of Formula I, its C-4 epimer and its oxidative degradation by-products by adding methylene at a concentration of 2-4 ml of methylene chloride per gram of compound of Formula I and at a pH between pH 6.5-8.0; and obtaining an extract containing methylene chloride, a compound of Formula I, and its C-4 epimer, said epimer being present in an amount of less than 3% of the amount of the compound of Formula I. |