Naltrexone

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Codeine is a component of gum opium and can also be produced by methylation of morphine using known prior art techniques.
A solution of codeine (30 g, 100.2 mmol), acetic anhydride (18.4 g, 180.2 mmol), triethylamine (18.25 g, 180.2 mmol) and 4-dimethylaminopyridine (0.5 g) in dry ethyl acetate (620 ml) was stirred at rt. under nitrogen for 12 hr, added saturated aqueous sodium bicarbonate solution until no acetic anhydride detected. The organic portion was separated, washed with water (3times 120 ml), dried over anhydrous sodium sulfate, and evaporated in vacuo to dryness to give 6-acetylcodeine as white solids (34.0 g, 99% yield).
Preparation of 6-acetylnorcodeine hydrochloride.
A solution of 6-acetylcodeine (10.0 g, 29.3 mmol), 1-chloroethyl chloroformate (5.51 g, 37.8 mmol), and proton sponge (1.0 g) in methylene chloride (80 ml) was heated at reflux for 80 min. The reaction mixture was evaporated in vacuo to dryness. The residue was chromatographed on silica gel with ethyl acetate to give 6-acetyl-17-(1-chloroethoxycarbonyl)norcodeine as an oil (12.13 g), which was dissolved in methanol with a few drops of conc. HCl. The solution was heated at reflux for 1 hr and evaporated in vacuo to almost dryness. The residue was added hexane and filtered to give 6- acetylnorcodeine hydrochloride (10.7 g, 100% yield).
Preparation of norcodeine hydrochloride.
A solution of 6-acetylcodeine (10.0 g, 29.3 mmol), 1-chloroethyl chloroformate (5.56 g, 38.1 mmol), and proton sponge (1.0 g) in methylene chloride (50 ml) was heated at reflux for 50 min. The reaction mixture was evaporated in vacuo to about 30 ml. Methanol (25 ml) and concentrated HCl (2 ml) were added. The solution was heated at reflux for 40 min. and evaporated in vacuo to almost dryness. The residue was added hexane and filtered to give norcodeine hydrochloride (8.8 g, 93% yield).
Preparation of 17-cyclopropylmethylnorcodeine.
A mixture of norcodeine hydrochloride (11.48 g, 27.8 mmol), (chloromethyl)cyclopropane (5.14 g, 55.6 mmol), sodium carbonate (14.73 g, 139.0 mmol), and potassium iodide (4.61 g, 27.8 mmol) in ethanol (250 ml) was heated at reflux for 20 hr, cooled, and evaporated in vacuo to dryness. The residue was basified with NH4OH, and extracted with methylene chloride. The extract was washed with water and evaporated in vacuo to dryness. The residue (11.7 g) was chromatographed on silica gel with a eluting solvent system of methanol/ethyl acetate (10/90) to give 17- cyclopropylmethylnorcodeine (10.68 g, 91% yield).
Preparation of 17-cyclopropylmethylnorcodeinone.