Triphenylphosphine → ethyl[(1R)-9-[(1S)-1-(4-chlorophenyl)ethyl]-6-fluoro-8-(methylsulfonyl)-2,3,4,9-tetrahydro-1H-carbazol-1-yl]acetate

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Reaction Steps

To a solution of the compound of Step 4 (1 eq), triphenylphosphine (1.5 eq) and (1R)-1-(4-chlorophenyl)ethanol (1.5 eq, prepared following the general procedure described in Reference Example 1) in THF (0.175M) was added a solution of di-tert-butyl azodicarboxylate (2.1 M in THF, 1.5 eq) over a 10 min period. The mixture was stirred at room temperature for 2 hr and concentrated. The residue was purified by silica gel flash chromatography, eluting with 7% EtOAc in toluene to give the desired product (˜90% pure) which was used as such for the next reaction.

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