Structure-activity studies of β-carbolines. 1. Molecular structure and conformation of cis-3-carboxylic acid-1,2,3,4-tetrahydroharmane dihydrate

The crystal structure of cis-3-carboxylic acid-1,2,3,4-tetrahydroharmane dihydrate, C 13 H 13 N 2 O 2 *2H 2 O, a putative ligand of the benzodiazepine receptor is reported. The space group is P2 1 /c with a = 14.850(4), b = 6.560(3), c = 14.746(4) Å and β = 117.411(8)°, Z = 4. The molecule crystallizes as a zwitterion with the unsaturated ring in a half-chair conformation. Hydrogen bonding to the water molecules included in the lattice determines the molecular packing arrangement.