PURPOSE: To prepare the tilted compound having higher whiteness and lower fluorescent intensity than those of the powder obtained by the slow crystallization, in high yield, by cooling the hot solution of a purine derivative to a definite temperature without stirring, and giving a sudden stimulation to the solution to effect the rapid crystallization.
CONSTITUTION: Crude crystals obtained by the rough purification of the reaction product at the first stage, are dissolved in 40W60 times of water under heat refluxing, mixed with a proper amount of activated charcoal, and heated for about 1hr to effect the decoloring of the solution. After removing the activated charcoal by filtration, the filtrate is left at rest, and cooled externally with water or ice water to ≤30°C. Acicular crystals are rapidly precipitated from the solution either by stirring the clear solution or by adding a small amount of seed crystal thereto, thereby destroying the supersaturated state.
EFFECT: The crystal obtained by the rapid crystallization has higher quality than the crystal obtained by the slow crystallization by 5W10% in terms of purification yield, 5W10% in terms of whiteness, and 50W60% in terms of fluorescent intensity.
SHIROSHITA TOORU
SUZUKI JIROU
