First synthesis of thiazepino[3,4-a]isoquinolines, a facile new synthetic route to diazepino[3,4-a]isoquinolines and assessment of their dopamine and σ receptor affinities.

Heterocycles that bear the novel 5,6,14,14a-tetrahydro-8H-benzo[6,7][1,4] thiazepino[3,4-a]isoquinoline and the 5,6,14,14a-tetrahydro-8H-13l2-benzo [6,7][1,4]diazepino[3,4-a]isoquinoline frameworks were synthesized in a facile manner. These tetrahydroprotoberberine (THPB)-inspired scaffolds demonstrate selective affinity for the σR in contrast to the naturally occurring THPB congeners that show DR and σR selectivity.

New tetrahydroisoquinoline-based DR ligands with an o-xylenyl linker motif.

The effect of rigidification of the n-butyl linker region of tetrahydroisoquinoline-containing DR ligands via inclusion of an o-xylenyl motif was examined in this study. Generally, rigidification with an o-xylenyl linker group reduces DR affinity and negatively impacts selectivity versus DR for compounds possessing a 6-methoxy-1,2,3,4,-tetrahydroisoquinolin-7-ol primary pharmacophore group. However, DR affinity appears to be regulated by the primary pharmacophore group and high affinity DR ligands with 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline and 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline primary pharmacophore groups were identified.

Inclusion of enclosed hydration effects in the binding free energy estimation of dopamine D3 receptor complexes.

Confined hydration and conformational flexibility are some of the challenges encountered for the rational design of selective antagonists of G-protein coupled receptors. We present a set of C3-substituted (-)-stepholidine derivatives as potent binders of the dopamine D3 receptor. The compounds are characterized biochemically, as well as by computer modeling using a novel molecular dynamics-based alchemical binding free energy approach which incorporates the effect of the displacement of enclosed water molecules from the binding site.

New Dopamine D3-Selective Receptor Ligands Containing a 6-Methoxy-1,2,3,4-tetrahydroisoquinolin-7-ol Motif.

A series of analogues featuring a 6-methoxy-1,2,3,4-tetrahydroisoquinolin-7-ol unit as the arylamine "head" group of a classical D3 antagonist core structure were synthesized and evaluated for affinity at dopamine D1, D2, and D3 receptors (D1R, D2R, D3R). The compounds generally displayed strong affinity for D3R with very good D3R selectivity. Docking studies at D2R and D3R crystal structures revealed that the molecules are oriented such that their arylamine units are positioned in the orthosteric binding pocket of D3R, with the arylamide "tail" units residing in the secondary binding pocket.