Synthesis and structure of 4-hy-droxy- N -iso-propyl-tryptamine (4-HO-NiPT) and its precursors.

The title compound, 4-hy-droxy- N -iso-propyl-tryptamine ( 4 ) or 4-HO-NiPT (systematic name: 3-{2-[(propan-2-yl)amino]-eth-yl}-1 H -indol-4-ol), C 13 H 18 N 2 O, was synthesized in three steps from 4-benzyl-oxyindole ( 1 ) (systematic name: 4-phen-oxy-1 H -indole), C 15 H 13 NO. ( 1 ) was treated with oxalyl chloride and iso-propyl-amine to produce N -isopropyl-4-benz-yloxy-3-indole-glyoxyl-amide ( 2 ) {systematic name: 2-[4-(benz-yloxy)-1 H -indol-3-yl]-2-oxo- N -(propan-2-yl)acet-amide}, C 20 H 20 N 2 O 3 . ( 2 ) was reduced to generate 4-benz-yloxy- N -iso-propyl-tryptamine (3) or 4-HO-NiPT, which was characterized as its chloride salt 4-benz-yloxy- N -iso-propyl-tryptammonium chloride ( 3a ) (systematic name: {2-[4-(benz-yloxy)-1 H -indol-3-yl]eth-yl}(propan-2-yl)aza-nium chloride), C 20 H 25 N 2 O·Cl. Finally the benzyl group of (3) was removed via hydrogenation to generate 4-HO-NiPT. The crystal structures of the title compound and all three synthetic precursors are presented.