METHOD FOR PREPARING CRYSTAL OF 4-[(5,6,7,8-TETRAHYDRO-5,5,8,8-TETRAMETHYL-2-NAPHTHALENYL)CARBAMOYL]BENZOIC ACID

摘要

A method for preparing a crystal of 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetrameth yl- 2-naphthalenyl)carbamoyl]benzoic acid having a single endothermic peak approximately at 233.degree.C in differential scanning calorimetry, which comprises the step of recrystallizing a crystal of 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2 - naphthalenyl)carbamoyl]benzoic acid from a mixture of water and ethanol. The method enables selective preparation of type-Il crystals which are stable against physical impact. The resulting crystals are free from highly toxic hexane as a residual solvent, and preferably used as an active ingredient of pharmaceuticals.