The present invention provides R,R′-atracurium salts, processes for producing and purifying such salts, and methods of using such salts to produce highly pure cisatracurium besylate.
1. A process for preparing an isomerically enriched R,R′-atracurium salt, the process comprising:
(a) admixing a salt of R,R′-atracurium with an acid;
(b) isolating an isomerically enriched salt of R,R′-atracurium by precipitation or cystallization; and
(c) optionally purifying the isomerically enriched salt;
wherein the isomerically enriched salt is enriched in the 1R-cis,1′R-cis isomer.
2. The process of claim 1 , wherein the salt of R,R′-atracurium used for admixing with an acid is selected from R,R′-atracurium besylate, R,R′-atracurium perchlorate, R,R′-atracurium tetrafluoroborate, R,R′-atracurium fluorosulfonate, R,R′-atracurium chloride and R,R′-atracurium bromide.
3. The process of claim 1 , wherein the anion of the R,R′-atracurium salt is replaced by contacting the R,R′-atracurium salt with an acid, which is at least one acid selected from tetrafluoroboric acid, perchloric acid and fluorosulfonic acid.
4. The process of claim 1 , wherein the isolation comprises precipitating the isomerically enriched salt.
5. The process of claim 1 , wherein the isomerically enriched salt is purified by slurrying in a solvent comprising tetrahydrofuran (THF), acetone, dioxane, diethyl ether, methyl ethyl ketone, ethyl acetate, or a mixture thereof.
6. The process of claim 5 , wherein the isomerically enriched salt is purified by crystallizing the salt from a solvent comprising tetrahydrofuran (THF), acetone, dioxane, diethyl ether, methyl ethyl ketone, ethyl acetate or a mixture thereof.
7. The process of claim 1 , wherein the purified isomerically enriched salt has at least one anion selected from perchlorate, tetrafluoroborate, and fluorosulfonate, and wherein the process further comprises converting the isomerically enriched salt into cisatracurium besylate.
8. The process of claim 7 , wherein the conversion of the isomerically enriched salt into cisatracurium besylate comprises contacting the isomerically enriched salt with an ion exchange resin comprising a besylate ion, subjecting the isomerically enriched salt to solid phase extraction in the presence of a besylate ion, or any combination of such methods.
9. The process of claim 8 , wherein the conversion comprises contacting an aqueous solution of the isomerically enriched R,R′-atracurium salt with a salt of benzenesulfonic acid, transferring the mixture through a stationary phase, eluting with at least one solvent, and evaporating the solvent.
10. The process of claim 9 , wherein evaporating the solvent comprises freeze drying or spray drying.
11. The process of claim 10 , wherein the obtained cisatracurium besylate has an isomeric purity of at least 99%.
12. An isomerically enriched R,R′-atracurium salt, which is R,R′-atracurium perchlorate, R,R′-atracurium tetrafluoroborate, or R,R′-atracurium fluorosulfonate.
13. The R,R′-atracurium salt of claim 12 , which is R,R′-atracurium perchlorate.
14. The R,R′-atracurium salt of claim 13 , wherein the X-ray powder diffraction (XRPD) pattern of the crystalline solid exhibits peaks at 4.0, 7.9, 9.3, 9.7, 12.8, 15.3, 15.8, 16.6, 17.4, 18.8, 19.4, 19.7, 21.0, 22.2, 23.7, 24.5, 25.0, 25.5, 26.9 and 28.4±0.2 degrees 2θ.
15. The R,R′-atracurium salt of claim 13 , which exhibits characteristic Infra-red (IR) bands at: 623, 725, 785, 866, 905, 984, 1024, 1086, 1267, 1325, 1377, 1458, 1518, 1589, 1611, 1726, 2112, 3553, 3586, and 3618 cm-1.
16. The R,R′-atracurium salt of claim 12 , which is R,R′-atracurium tetrafluoroborate.
17. The R,R′-atracurium salt of claim 16 , wherein the X-ray powder diffraction pattern of the crystalline solid exhibits peaks at 3.9, 7.8, 9.2, 9.7, 10.4, 12.7, 15.3, 16.6, 17.3, 18.7, 19.2, 21.1, 22.2, 23.6, 24.3, 24.9, 25.3, 26.8 and 28.2±0.2 degrees 2θ.
18. The R,R′-atracurium salt of claim 16 , which exhibits characteristic IR bands at: 723, 868, 1057, 1611, 1267, 1377, 1460, 1518, 1591, 1611, 1726, and 3586 cm-1.