Patent ID: 6936718

Claim:
A process for preparing a mixture of rotamers or rotamer pairs of a salt of a basic compound of Formula I: wherein said mixture comprises either (i) the 1-rotamer in a higher molar percent than the 2-rotamer of said salt, or (ii) the 2-rotamer in a higher molar percent than the 1-isomer of said salt, or (iii) the 1,2-rotamer pair in a higher molar percent than the 3,4-rotamer pair of said salt, or (iv) the 3,4-rotamer pair in a higher molar percent than the 1,2-rotamer pair of said salt, said process comprising reacting said basic compound with an acid in admixture with a solvent wherein said solvent is a ketone, ether, hydrocarbon or mixtures thereof, with said solvent being used in a ratio about 15:1 with respect to said basic compound, further wherein said 1-rotamer (structure A), 2-rotamer (structure B), 3-rotamer (structure C) and 4-rotamer (structure D) elute in the order 1, 2, 3 and 4 from a chiral HPLC column, and are shown by their following diastereomeric structures due to restricted rotation of bonds marked a and b in Formula I: