合成路线1

The known indole-2-carboxylate intermediate (I) was protected as the N-benzenesulfonyl derivative (II) using benzenesulfonyl chloride and NaH, and the tert-butyl ester group of (II) was subsequently cleaved by means of formic acid. The resulting carboxylic acid (III) was activated as the 2-pyridyl thioester (IV) upon treatment with 2,2'-dipyridyl disulfide and triphenylphosphine. Selective protection of 4-aminobenzyl amine (V) with Boc2O produced the amino carbamate (VI). This was coupled with pyridyl thioester (IV) in refluxing THF to yield amide (VII). Subsequent removal of the N-Boc group of (VII) with trifluoroacetic acid afforded the free amino derivative (VIII), which was converted to the required urea (IX) upon treatment with trimethylsilyl isocyanate. Further hydrolysis of the benzenesulfonyl group of (IX) with ethanolic NaOH furnished the deprotected indole (X).