Akademik Veri Yönetim Sistemi
BORON2025 International Boron Symposium, Ankara, Türkiye, 3 - 05 Aralık 2025, ss.1, (Özet Bildiri)
When a central atom is tetra-coordinated, the compound becomes optically active by having four different atoms or groups surrounding it. The complexation of boronic acids with Schiff base ligand is a common way to acquire tetra-coordinated boron atoms. The use of chiral Schiff base ligands has resulted in the synthesis of diastereomerically and enantiomerically pure macrocyclic boronates (boron complexes), but the chirality of these compounds is not solely due to the boron atom. On the other hand, in the studies of macrocyclic boronates with Schiff base ligands, chirality only at the boron atom is much less common. Our approach has been to develop macrocyclic boronates, with the two boron atoms being tetra-coordinated to improve stability, and chirality is only seen in the boron atoms. Therefore, we have utilized achiral tetradentate salenH2 type symmetrical bulky ligands (1) which have two imine groups in their structures to react with dibenzofuran-4-boronic acid. In this study, we have synthesized a series of new macrocyclic boronates containing a planar and bulky dibenzofuranyl group with two different architectural types for the investigation of their spectral and chiral properties, and DNA cleavage activities. Firstly, salenH2 ligands [HOArCH=N-R-N=CH-ArOH (1); R=(CH2)n, n=2-4, and R=(CH2CH(OH)CH2)] were obtained from the reactions of salicylaldehyde with 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane and 2-hydroxy-1,3-diaminopropane, respectively, in dry MeOH. Dibenzofuran-4-boronic acid and salenH2 type ligands (1) were brought to condensation reactions in a 2:1 stoichiometry in toluene to obtain dinuclear macrocyclic boronates with a boroxane group (RB-O-BR) (2). Trinuclear macrocyclic boronates (3) with a boroxine group (B-O-B)-(O2BPh), were synthesized through the combination of boric acid/dibenzofuran-4-boronic acid and salenH2 type ligands (1) in asetonitrile. Macrocyclic boronates contain a central seven-, eight- and nine-membered heterocycles [(B-O-B)-(N-CH2-R-CH2-N)] with an oxygen atom bridging two boron atoms, and possess two equivalent chiral boron centers. The structures of the macrocyclic boronates were characterized by elemental analysis, FTIR, MS, 1D 1H, 13C and 11B NMR, and 2D HSQC techniques. It was determined from the NMR spectra that dinuclear (2) and trinuclear (3) macrocyclic boronates had only one stereoisomer, and from the circular dichroism (CD) spectra it was determined that they had only one of the enantiomers. The literature is lacking sufficient research on the interaction of dibenzofuran derivatives with DNA, but it has been demonstrated that dibenzofuran derivatives interact with DNA and bind to it through intercalation. Therefore, the gel electrophoresis and UV titration methods were employed to examine interactions between DNA and macrocyclic boronates. It was found that dinuclear macrocyclic boronates did not have any effect on DNA but did cause it to precipitate in the gel. DNA was damaged at a high concentration of trinuclear macrocyclic boronate [R=(CH2CH(OH)CH2)].