171087-98-2Relevant academic research and scientific papers
Synthesis of bis(catechol) ligands derived from Troeger's base and their dinuclear triple-stranded complexes with titanium(IV) ions
Kiehne, Ulf,Luetzen, Arne
, p. 5703 - 5711 (2008/09/17)
Bis(catechol) ligands derived from 2,8-disubstituted analogues of Troeger's base and monofunctionalized MOM-protected or unprotected catechols bearing both rigid and flexible spacers were synthesized, which gave rise to dissymmetric oxygen donor ligands w
Macrotricyclic Steroid Receptors by Pd°-Catalyzed Cross-Coupling Reactions: Dissolution of Cholesterol in Aqueous Solution and Investigations of the Principles Governing Selective Molecular Recognition of Steroidal Substrates
Marti, Thomas,Peterson, Blake R.,Fuerer, Andreas,Mordasini-Denti, Tiziana,Zarske, Juergen,Jaun, Bernhard,Diederich, Francois,Gramlich, Volker
, p. 109 - 144 (2007/10/03)
Three double-decker cyclophane receptors, (±)-2,(±)-3, and (±)-4 with 11-13-A deep hydrophobic cavities were prepared and their steroid-binding properties investigated in aqueous and methanolic solutions. Pd°-Catalyzed cross-coupling reactions were key steps in the construction of these novel macrotricyclic structures. In the synthesis of D2-symmetrical (±)-2, the double-decker precursor (±)-7 was obtained in 14% yield by fourfold Stille coupling of equimolar amounts of bis(tributylstannyl)acetylene with dibromocyclophane 5 (Scheme 1). For the preparation of the macrotricyclic precursor (±)-15 of D2-.symmetrical (±)-3, diiodocylophane 12 was dialkynylated with Me3SiC≡CH to give 13 using the Sonogoshira cross-coupling reaction; subsequent alkyne deprotection yielded the diethynylated cyclophane 14, which was transformed in 42% yield into (±)-15 by Glaser-Hay macrocyclization (Scheme 2). The synthesis of the C2-symmetrical conical receptor (±)-4 was achieved via the macrotricyclic precursor (±)-25, which was prepared in 20% yield by the Hiyama cross-coupling reaction between the diiodo[6.1.6.1]paracyclophane 19 and the larger, dialkynylated cyclophane 17 (Scheme 4). Solid cholesterol was efficiently dissolved in water through complexation by (±)-2 and (±)-3, and the association constants of the formed 1:1 inclusion complexes were determined by solid-liquid extraction as Ka = 1.1 × 106 and 1.5 × 105 1 mol-1, respectively (295 K) (Table 1). The steroid-binding properties of the three receptors were analyzed in detail by 1H-NMR binding titrations in CD3OD. Observed steroid-binding selectivities between the two structurally closely related cylindrical receptors (±)-2 and (±)-3 (Table 2) were explained by differences in cavity width and depth, which were revealed by computer modeling (Fig. 4). Receptor (±)-2, with two ethynediyl tethers linking the two cyclophanes, possesses a shallower cavity and, therefore, is specific for flatter steroids with a C(5)=C(6) bond, such as cholesterol. In contrast, receptor (±)-3. constructed with longer buta-1,3-diynediyl linkers, has a deeper and wider hydrophobic cavity and prefers fully saturated steroids with an aliphatic side chain, such as 5α-cholestane (Fig. 7). In the 1:1 inclusion complexes formed by the conical receptor (±)-4 (Table 3), testosterone or progesterone penetrate the binding site from the wider cavity side, and their flat A ring becomes incorporated into the narrower [6.1.6.1]paracyclophane moiety. In contrast, cholesterol penetrates (±)-4 with its hydrophobic side chain from the wider rim of the binding side. This way, the side chain is included into the narrower cavity section shaped by the smaller [6.1.6.1]paracyclophane, while the A ring protrudes with the OH group at C(3) into the solvent on the wider cavity side (Fig. 8). The molecular-recognition studies with the synthetic receptors (±)-2, (±)-3, and (±)-4 complement the X-ray investigations on biological steroid complexes in enhancing the understanding of the principles governing selective molecular recognition of steroids.
Synthesis of linear oligo(catechol) ligands for the metal directed self-assembling of helicates
Albrecht, Markus
, p. 230 - 236 (2007/10/03)
The synthesis of the oligo(catechol) systems 1-4 with different substituents, length of the connecting spacer, and number of catechol units is achieved by the use of various coupling reactions (e.g. Wurtz, Glaser-Eglinton, Stephens-Castro). In order to do this methods of preparing the building blocks, 2,3-dimethoxybenzyl bromides 5, 2,3-dimethoxyphenylacetylene (17), or 1,4-dibromo-2,3-dimethoxybenzene (23) have been developed starting with simple catechol (benzene-1,2-diol) derivatives.
Bildung eines "meso-Helicats" durch Selbstorganisation von drei Bis(brenzkatechinat)-Liganden und zwei Titan(IV)-Ionen
Albrecht, Markus,Kotila, Sirpa
, p. 2285 - 2287 (2007/10/03)
Keywords: Brenzkatechin; Komplexe mit Sauerstoffliganden; Selbstorganisation; Titanverbindungen
