Patent ID: 8357805

Claim:
A method of separating the 1R-cis,1′R-cis isomer (cisatarcurium) from (1R,1′R)-atracurium salt isomer mixture, the method comprising: (a) loading the (1R,1′R)-atracurium salt isomer mixture onto a chromatographic column comprising a stationary phase suitable for normal phase flash chromatography; (b) eluting with an eluant at low to medium pressure, to elute from the column one or more fractions comprising a cisatracurium salt, which is substantially free of other (1R,1′R)-atracurium isomers; (c) collecting one or more of the fractions, to obtain a cisatracurium salt, which is substantially free of other (1R,1′R)-atracurium isomers; (d) optionally performing an ion exchange; and (e) isolating the cisatracurium salt wherein step (b) comprises eluting with a non-aqueous mobile phase comprising a weak organic acid.