Novel isoquinolinium compounds useful in the preparation of cisatracurium and associated intermediates

A compound having the structural formula (X)

• and acid addition salts thereof, wherein Y is OR1 or NR2R3, wherein R1 is alkyl, aryl or heteroaryl, and R2 and R3 are the same or different and each is independently hydrogen, alkyl, aryl or heteroaryl, with the proviso that Y is not OH, or an acid addition salt thereof (IX).

A crystalline compound of the formula:

• wherein X− is an anion selected from chloride, bromide, iodide, methanesulfonate, benzenesulfonate, p-toluenesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, tetrafluoroborate, oxalate, and tartarate.

A method for preparing cisatracurium, the method comprising converting a compound of the formula

• into cisatracurium by coupling it with 1,5-pentanediol to produce the cisatracurium.