Patent ID: 7414114

Claim:
A process for preparing an anhydrous compound having formula I: wherein R 1 represents hydrogen, (C 1 -C 6 )-alkyl, (C 6 -C 10 )-aryl or (C 7 -C 16 )-aralkyl; and each R 2 , R 3 , R 4 , R 5 and R 6 individually represents hydrogen or (C 1 -C 4 )alkyl; consisting essentially of removing, by distillation, a halo(C 1 -C 6 )alkane solvent from a solution prepared by dissolving a hydrated compound of Formula I and water in the halo(C 1 -C 6 )alkane solvent so as to provide the anhydrous compound through removal of the water from the solution by co-distillation or azeotropic distillation of the water with the solvent.