Chloride → Gabapentin hydrochloride

Participants

Reaction Steps

is dissolved in chloride free demineralized water (375 ml) at 50 degrees. The solution is treated with charcoal at the same temperature and filtered through a bed of hyflo. The bed is washed with demineralized water (150 ml). The filtrate is cooled to 10 deg and neutralized with sodium lye (110 g of 50% w/w sodium hydroxide solution) with the temperature kept strictly below 15 degrees. The neutralized mixture is heated to 70-75 degrees over a period of 3 hours to get a clear solution, then cooled to 5-10 degrees over a period of 4 hours and kept at that temperature range for 1 hr and filtered (mother liquor A). The product is suck dried thoroughly to give moist gabapentin (about 195 g) having water content of 14%. This is dissolved in a mixture of methanol (570 ml) and water (60 ml) at about 70 degrees. The solution is treated with activated charcoal (5 g) and filtered through a bed of hyflo. The bed is washed with a mixture of methanol (80 ml) and water (16 ml). To the combined filtrates is added isopropanol (815 ml). The mixture is cooled to 0-5 degrees and maintained for 1 hr, when pure white gabapentin crystallizes out, the mixture is centrifuged; the product is spin-dried for 45 min (mother liquor B) and dried to yield gabapentin (125 g) with 1. Chloride 40 ppm, 2. Gabalactam, 0.01%, 3. Impurity with RF 0.5 relative to gabapentin NIL 4. Any other individual impurity less than 0.1% 5. Total impurities 0.032%

Provenance & Evidence