Naloxegol Oxalate

Naloxegol oxalate (XXI) is a peripherally acting μ-opioid receptor antagonist that was approved in the USA and EU for the treatment of opioid-induced constipation in adults with chronic non-cancer pain. The drug, a pegylated version of naloxone, has significantly reduced central nervous system (CNS) penetration and works by inhibiting the binding of opioids in the gastrointestinal tract. Naloxegol oxalate was developed by Nektar and licensed to AstraZeneca. Although we were unable to find a single report in the primary or patent literature that describes the exact experimental procedures to prepare naloxegol oxalate, there have been reports on the preparation of closely related analogs with specific reports on improving the selectivity of the reduction step156 and the salt formation of the final drug substance.

Naloxegol Oxalate is an oxalate form of Naloxegol (N284470) which is a peripherally-selective opioid antagonist.

Naloxone (180) was treated with methoxyethyl chloride in the presence of Hunig?ˉs base to give the protected ketone 181. Reduction of the ketone with potassium trisec- butylborohydride exclusively provided the a-alcohol 182 in 85% yield. Alternatively, sodium trialkylborohydrides could also be used to provide similar a-selective reduction in high yield. Deprotonation of the alcohol with sodium hydride followed by alkylation with CH3(OCH2CH2)7Br (183) provided the pegylated intermediate 184 in 88% yield. Acidic removal of the methoxyethyl ether protecting group followed by treatment with oxalic acid and crystallization provided naloxegol oxalate (XXI) in good yield.