Diisopropylethylamine → (S)-1-((S)-2-(3-azidopropyl)-5-(2,5-difluorophenyl)-2-phenyl-1,3,4-thiadiazol-3(2H)-yl)-2-(t-butyldiphenylsilyloxy)propan-1-one

Participants

Reaction Steps

To a solution of (S)-2-(t-butyldiphenylsilyloxy)propanoic acid (339 mg, 1.09 mmol) in acetonitrile (6 mL) was added HATU (550 mg, 1.45 mmol) followed by DIEA (0.378 mL, 2.17 mmol). After stirring at room temperature for 15 minutes, a solution of 2-(3-azidopropyl)-5-(2,5-difluorophenyl)-2-phenyl-2,3-dihydro-1,3,4-thiadiazole (260 mg, 0.72 mmol) in acetonitrile (4 mL) was added. After stirring at room temperature for 16 hours, the mixture was concentrated under reduced pressure and partitioned between saturated NaHCO3 (50 mL) and ethyl acetate (50 mL). The aqueous layer was extracted with ethyl acetate (2×30 mL) and the combined organic phases were washed with brine (20 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The brown oil was chromatographed (9:1 hexanes/ethyl acetate) to provide the less polar diastereomer, (S)-1-((S)-2-(3-azidopropyl)-5-(2,5-difluorophenyl)-2-phenyl-1,3,4-thiadiazol-3(2H)-yl)-2-(t-butyldiphenylsilyloxy)propan-1-one (121 mg) and the more polar diastereomer, (S)-1-((R)-2-(3-azidopropyl)-5-(2,5-difluorophenyl)-2-phenyl-1,3,4-thiadiazol-3(2H)-yl)-2-(t-butyldiphenylsilyloxy)propan-1-one (175 mg) as pale yellow oils. Absolute stereochemistry was assigned by examination of a protein:inhibitor co-crystal structure of Eg5 and (S)-1-((S)-2-(3-aminopropyl)-5-(2,5-difluorophenyl)-2-phenyl-1,3,4-thiadiazol-3(2H)-yl)-2-methoxypropan-1-one.

Provenance & Evidence