反应详情

Minocycline/HCl salt (200 g, 0.406 mol) was suspended in 3 L water and an amount of NaHCO3 (34 g, 0.406 mol) was added in 3 portions and the pH was adjusted to 6.5-7.0. The solution was then extracted with 2×1.5 L CH2Cl2. The solution was concentrated to dryness to give minocycline as the freebase, then redissolved in THF (1.6 L) and was charged in a 3 L 3-necked flask equipped with an over-head stirrer and a temperature probe while under argon. An amount of methyl iodide (289 g, 2.03 mol) was added and the solution was heated at 40-45° C. for approximately 16 hours, at which point it was verified by HPLC that no minocycline was left in solution. The solution was then poured into 6 L of heptane while on ice bath and stirred for at least 20 minutes at <5° C. The precipitate was filtered and washed with hexane (400 mL). The solid was dried under reduced pressure to a constant weight. An amount of 186 g methylammonium salt of minocycline was isolated.

1. extractionThe solution was then extracted with 2×1.5 L CH2Cl2
2. concentrationThe solution was concentrated to dryness