Corticosteroid decomposition via a mixed anhydride.
Oxidation of dexamethasone in an aqueous suspension by air during prolonged storage produces the 17alpha-formyloxy-17beta-carboxylic acid 4. A pathway to 4 is proposed that involves Baeyer-Villiger-type oxidation of keto aldehyde 1 to mixed anhydride 5, followed by intramolecular formyl transfer. Synthetically, acid 3 was reacted with N,N'-carbonyldiimidazole followed by triethylammonium formate in order to generate the transient anhydride 5 en route to an authentic sample of 4.
Conrow
Raymond E
RE
Alcon Research, Ltd., 6201 South Freeway, Fort Worth, Texas 76134, USA. ray.conrow@alconlabs.com
Dillow
Glen W
GW
Bian
Liangqiao
L
Xue
Liang
L
Papadopoulou
Olga
O
Baker
John K
JK
Scott
Britt S
BS