Pyridine → (S)-2-[2-(tert-Butyl-dimethyl-silyloxy)-ethyl]-4-[2-(3-fluoro-2-methyl-benzyl)-1-phenyl-indolizine-3-carbonyl]-piperazine-1-carboxylic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

The compound of example 1, step 3 (1.00 g, 3.17 mmol) was dissolved in 15 ml of DCM and cooled to 0° C. To this solution was added pyridine (0.26 ml, 3.17 mmol) and a 20% solution of phosgene in toluene (1.67 ml, 3.17 mmol) and the mixture was stirred for 2.5 h at room temperature. This solution was then added dropwise to a solution of the compound of step 3 (1.202 g, 3.49 mmol) in 25 ml of DCM containing triethylamine (0.44 ml, 3.49 mmol) and the mixture stirred overnight at room temperature. DCM (25 ml) was added and the solution was washed with 25 ml of 0.5 N hydrochloric acid, 25 ml of a saturated solution of sodium hydrogencarbonate and 25 ml of brine. The organic phase was dried over sodium sulfate, filtered and evaporated to dryness under reduced pressure. The residue was purified by chromatography on silica gel (cyclohexane/EA, 85:15, then 80:20) to give 1.33 g of the title compound as an off-white powder melting at 70° C.

Provenance & Evidence