In the title compound, C25H29FO4, each cyclo­hexenone ring has an envelope conformation with the dimethyl-substituted atom as the flap. The hy­droxy and carbonyl groups form two intra­molecular O—H⋯O hydrogen bonds, as is typical for xanthene derivatives. In the crystal, very weak C—H⋯O hydrogen bonds link mol­ecules into dimers.

In the title compound, C21H16N2O2, the 3-nitro­phenyl and two phenyl rings are twisted from the mean plane of the enimino fragment by 44.4 (1), 37.2 (1) and 74.1 (1)°, respectively. The crystal packing exhibits no classical inter­molecular contacts.

In the title compound, C21H16N2O2, the dihedral angles between the mean planes of the 4-nitro­phenyl ring and the two phenyl rings are 57.3 (5) and 16.8 (6)°. The imine group displays a C—C—N—C torsion angle of −24.9 (3)°.

In the title compound, C25H29NO6, each of the cyclo­hexenone rings adopts a half-chair conformation. The hy­droxy and carbonyl O atoms face each other and are oriented to allow for the formation of two intra­molecular O—H⋯O hydrogen bonds. In the crystal, weak C—H⋯O hydrogen bonds are formed between molecules, generating a two-dimensional supramolecular structure.

In the title compound, C25H27NO5, each of the cyclo­hexenone rings adopts a half-chair conformation, whereas the six-membered pyran ring adopts a flattened boat conformation, with the O and methine C atoms deviating from the plane of the other four atoms. In the crystal, weak C—H⋯O hydrogen bonds link mol­ecules into chains parallel to the c axis.

In the title compound, C21H19ClO3, the two cyclo­hexenone rings adopt half-chair conformations, whereas the pyran ring adopts a boat conformation. The 4-chloro­phenyl ring is almost perpendicular to the plane through the four C atoms of the pyran ring [dihedral angle = 87.97 (6)°]. In the crystal, weak C—H⋯O hydrogen bonds link the mol­ecules into a chain parallel to the a-axis.

In the title compound, C22H22O4, the two cyclo­hexenone rings adopt half-chair conformations, whereas the six-membered pyran ring adopts a flattened boat conformation, with the O and methine C atoms deviating from the plane of the other four atoms by 0.142 (2) and 0.287 (2)Å, respectively. In the crystal, weak C—H⋯O hydrogen bonds link mol­ecules into chains running parallel to the a axis.

In the title compound, C21H21NO6, each of the cyclo­hexenone rings adopts a half-chair conformation. Each of the pairs of hy­droxy and carbonyl O atoms are oriented to allow for the formation of intra­molecular O—H⋯O hydrogen bonds, which are typical of xanthene derivatives.

In the title compound, C22H21ClO2, the oxolane ring adopts a twisted conformation. The dihedral angles between the mean plane of the oxolane ring and the mean planes of the 4-chloro­phenyl, phenyl and cyclo­pentenyl rings are 71.81 (18), 76.9 (18) and 82.08 (18)°, respectively.

In the title compound, C27H26O4, each of the cyclo­hexenone rings adopts a half-chair conformation. The dihedral angle between the two phenyl rings is 89.53 (5)°. The hy­droxy and carbonyl O atoms face each other and are orientated to allow the formation of two intra­molecular O—H⋯O hydrogen bonds, which are typical of xanthene derivatives.

In the title compound, C25H29NO6, each of the cyclo­hexenone rings adopts a half-chair conformation. Each of the pairs of hy­droxy and carbonyl O atoms are oriented to allow for the formation of intra­molecular O—H⋯O hydrogen bonds, which are typical of xanthene derivatives. The nitro group is rotationally disordered over two orientations in a 0.544 (6):0.456 (6) ratio. In the crystal, weak inter­molecualr C—H⋯O hydrogen bonds link mol­ecules into layers parallel to the ab plane.

In the title compound, C22H24O5, each of the cyclo­hexenone rings adopts a half-chair conformation. The hy­droxy and carbonyl O atoms face each other and are orientated to allow for the formation of the two intra­molecular O—H⋯O hydrogen bonds which are typical of xanthene derivatives. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into layers parallel to the ab plane.

The serotonin transporter (SERT) terminates neurotransmission by removing serotonin from the synaptic cleft. In addition, it is the site of action of antidepressants (which block the transporter) and of amphetamines (which induce substrate efflux). We explored the functional importance of the N terminus in mediating the action of amphetamines by focusing initially on the highly conserved threonine residue at position 81, a candidate site for phosphorylation by protein kinase C. Molecular dynamics simulations of the wild type SERT, compared with its mutations SERTT81A and SERTT81D, suggested structural changes in the inner vestibule indicative of an opening of the inner vestibule. Predictions from this model (e.g. the preferential accumulation of SERTT81A in the inward conformation, its reduced turnover number, and a larger distance between its N and C termini) were verified. Most importantly, SERTT81A (and the homologous mutations in noradrenaline and dopamine) failed to support amphetamine-induced efflux, and this was not remedied by aspartate at this position. Amphetamine-induced currents through SERTT81A were comparable with those through the wild type transporter. Both abundant Na+ entry and accumulation of SERTT81A in the inward facing conformation ought to favor amphetamine-induced efflux. Thus, we surmised that the N terminus must play a direct role in driving the transporter into a state that supports amphetamine-induced efflux. This hypothesis was verified by truncating the first 64 amino acids and by tethering the N terminus to an additional transmembrane helix. Either modification abolished amphetamine-induced efflux. We therefore conclude that the N terminus of monoamine transporters acts as a lever that sustains reverse transport.