2-(3-Oxo-3,4-dihydro-2H-1,4-benzothia-zin-4-yl)acetohydrazide

Development and Characterization of Novel Selective, Non-Basic Dopamine D2 Receptor Antagonists for the Treatment of Schizophrenia

The dopamine D₂ receptor, which belongs to the family of G protein-coupled receptors (GPCR), is an important and well-validated drug target in the field of medicinal chemistry due to its wide distribution, particularly in the central nervous system, and involvement in the pathomechanism of many disorders thereof. Schizophrenia is one of the most frequent diseases associated with disorders in dopaminergic neurotransmission, and in which the D₂ receptor is the main target for the drugs used. In this work, we aimed at discovering new selective D₂ receptor antagonists with potential antipsychotic activity. Twenty-three compounds were synthesized, based on the scaffold represented by the D2AAK2 compound, which was discovered by our group. This compound is an interesting example of a D₂ receptor ligand because of its non-classical binding to this target. Radioligand binding assays and SAR analysis indicated structural modifications of D2AAK2 that are possible to maintain its activity. These findings were further rationalized using molecular modeling. Three active derivatives were identified as D₂ receptor antagonists in cAMP signaling assays, and the selected most active compound 17 was subjected to X-ray studies to investigate its stable conformation in the solid state. Finally, effects of 17 assessed in animal models confirmed its antipsychotic activity in vivo.

Crystal structure of (E)-2-benzyl-idene-4-[(3-phenyl-4,5-di-hydro-isoxazol-5-yl)meth-yl]-2H-benzo[b][1,4]thia-zin-3(4H)-one

In the title compound, C₂₅H₂₀N₂O₂S, the di­hydro­isoxazole ring exhibits an envelope conformation with the methine atom being the flap, while the 1,4-thia­zine ring displays a screw-boat conformation. The six-membered ring fused to the 1,4-thia­zine ring makes dihedral angles of 63.04 (2) and 54.7 (2)° with the mean planes through the five-membered heterocycle and the attached phenyl ring, respectively. The phenyl group connected to the 1,4-thia­zine ring is disordered over two sites [major component = 0.57 (2)]. The most prominent inter­actions in the crystal structure are C—H⋯O hydrogen bonds that link mol­ecules, forming inversion dimers, and C—H⋯N hydrogen bonds that link the dimers into columns parallel to the b axis.

(2Z)-2-Benzyl-idene-4-n-butyl-3,4-di-hydro-2H-1,4-benzo-thia-zin-3-one

In the title compound, C19H19NOS, the six-membered hetero-cyclic ring of the benzo-thia-zine fragment exhibits a screw boat conformation. The plane of the fused benzene ring makes a dihedral angle of 72.38 (12)° with that of the terminal phenyl ring, and is nearly perpendicular to the mean plane formed by the atoms through the n-butyl chain, as indicated by the dihedral angle of 88.1 (2)°. In the crystal, mol-ecules are linked by C-H⋯O inter-actions to form supra-molecular chains along [110].

Methyl 2-(3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetate

In the crystal structure of the title compound, C₁₁H₁₁NO₃S, the mol­ecules are linked by inter­molecular C—H⋯O hydrogen-bond inter­actions. The heterocyclic thia­zine ring adopts a conformation inter­mediate between twist and boat.

2-(3-Oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetamide

In the title compound, C₁₀H₁₀N₂O₂S, the thia­zine ring approximates to an envelope form with the S atom in the flap position. The amide group attached to the acetate group is almost perpendicular to the mean plane of the thia­zine ring [dihedral angle = 88.83 (8)°]. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds occur. Further N—H⋯O and C—H⋯O hydrogen bonds link the dimers into a three-dimensional network.