Molecular and absolute crystal structure of pindolol-1-(1H-indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol: A specific beta-adrenoreceptor antagonist with partial agonist activity

The crystal and molecular structure of pindolol, 1-(1H indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol, has been determined by direct methods. Crystals are tetragonal, ,a=b=15.809(4),c=11.246(2) Å,Z=8,D _c=1.174 mg m^–3. The finalR-factor for 2271 reflections withI>2(I) is 0.038. Refinement by full-matrix least-squares on F² also enabled the absolute configuration of the structure to be established. The molecule is essentially planar, including much of the side-chain which is stabilized by the existence of two intramolecular H-bonds, between the ethyl oxygen and OH group, and between the OH and side-chain amide groups, respectively. The crystal structure is formed by three intermolecular hydrogen bonds including two side-chain-side-chain interactions, between ethyl oxygen to amide and OH to amide, and an interaction between the side-chain OH to indole NH.