Áron Pintér

Synthesis of novel fluorescent acridono- and thioacridono-18-crown-6 ligands

Abstract Novel fluorescent 18-crown-6 type ligands containing acridono and thioacridono units were synthesised. The acridono ligand was prepared by the oxidation of its acridino analogue, and also by the cyclisation of 4,5-dihydroxyacridine-9(10 H )-one and tetraethylene glycol di- p -tosylate in the presence of K 2 CO 3 . The acridono macrocycle was converted to the thioacridono ligand using Lawessonss Reagent. The synthesis of several precursors leading to the preparation of an acridono-18-crown-6 fluorophore was also performed. These precursors can also be very useful building blocks for acridine, acridone and thioacridone derivatives of chemotherapeutical importance.

1,7-Electrocyclisations of stabilised azomethine ylides

Ester-stabilized a,b:g,d-unsatd. azomethine ylides were generated by the deprotonation method from isoquinolinium salts. 1,7-Electrocyclization of these dipoles followed by a 1,5-hydrogen shift, gives tetrahydro[5,6]azepino[2,1-a]isoquinolines I (R = MeO2C, PhCH2, PhCO, CH2:CHCH2).

A very stable complex of a modified marine cyclopeptide with chloroform

Noncovalent interactions play a pivotal role in molecular recognition. These interactions can be subdivided into hydrogen bonds, cation-π interactions, ion pair interactions and London dispersion forces. The latter are considered to be weak molecular interactions and increase with the size of the interacting moieties. Here we show that even the small chloroform molecule forms a very stable complex with a modified marine cyclopeptide. By means of high-level quantum chemical calculations, the size of the dispersive interactions is calculated; the dispersion energy (approximately -40 kcal mol⁻¹) is approximately as high as if the four outer atoms of the guest form four strong hydrogen bonds with the host. This strong binding of chloroform to a modified marine cyclopeptide allows the speculation that the azole-containing cyclopeptides-haloform interaction may play some biological role in marine organisms such as algae.

Synthesis of pyrrolo[3,4-c]quinolines by 1,5-electrocyclisation of non-stabilised azomethine ylides

A new route to the pyrrolo[3,4-c]quinoline ring system was developed via the 1,5-dipolar electrocyclization reactions of azomethine ylides derived from easily available 3-formylquinoline derivs. The intermediacy of azomethine ylides was shown by the trapping of the proposed dipoles with N-phenylmaleimide.