A solution of ammonia in methanol (7 M) (5.1 ml, 35 mmol) was added to a suspension of (RS)-5-chloro-pyridine-2-carboxylic acid [3-(3-cyclopropyl-5-thioxo-morpholin-3-yl)-4-fluoro-phenyl]-amide (=5-chloro-pyridine-2-carboxylic acid [3-((RS)-3-cyclopropyl-5-thioxo-morpholin-3-yl)-4-fluoro-phenyl]-amide) (0.240 g, 0.59 mmol) in methanol (18 ml). Thereafter, tent-butyl hydroperoxide (70% in water) (0.81 ml, 5.9 mmol) was added at room temperature and the mixture stirred for 16 hours. For the workup, the clear solution was evaporated at reduced pressure. The residue was purified by chromatography on silica gel using a 80:10:1-mixture of ethyl acetate, methanol, and ammoniumhydroxide as the eluent. The pure fractions were combined and evaporated, then the residue was treated with a mixture of dichloromethane and water. After evaporation of the organic layer, the 5-chloro-pyridine-2-carboxylic acid [3-((RS)-5-amino-3-cyclopropyl-3,6-dihydro-2H-[1,4]oxazin-3-yl)-4-fluoro-phenyl]-amide (22) was obtained as a white solid (99 mg, 43% of theory). Mass (calculated) C19H18ClFN4O2S [388.828]; (found) [M+H]+=389.
