Borbála Vermes

Synthesis of novel acridino- and phenazino-18-crown-6 ligands and their optically pure dimethyl-substituted analogues for molecular recognition studies

Abstract Novel acridino- and phenazino-18-crown-6 ligands 5 and 6 were prepared from acridine-4,5-diol (9) and phenazine-1,9-diol (10) with tetraethylene glycol di-p-tosylate (11) using potassium teri-butoxide as a base in THF. New optically pure dimethyl-substituted acridino- and phenazino-18-crown-6 ligands (R,R)-7 and (R,R)-8 were also prepared by treating 9 and 10 with optically pure dimethyl-substituted tetraethylene glycol di-p-tosylate [(S,S)-18] . Molecular recognition studies on these novel ligands are underway.

Luminescence signalled enantiomeric recognition of chiral organic ammonium ions by an enantiomerically pure dimethylacridino-18-crown-6 ligand

Acridino-18-crown-6 ligands 1 and 2 are able to bind organic ammonium salts in acetonitrile with high affinity, causing pronounced changes in the luminescence properties of the two partners. Furthermore, enantiomerically pure chiral ligand 2 shows a high enantioselectivity towards chiral organic ammonium ions. The observed changes in the photophysical properties are also an important tool for understanding the interactions present in the adduct. The possibility of monitoring the binding process by means of such a sensitive technique as photoluminescence spectroscopy can gain ground for the design of very efficient enantioselective chemosensors for chiral species.

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.

Total synthesis of plagiochins C and D, macrocyclic bis(bibenzyl) constituents of plagiochila acantophylla

Abstract Plagiochins C ( 3 ) and D ( 4 ) were synthesized by convergent schemes. Rings C and B were joined by Ullman ether synthesis, the arylaryl bond between rings A and D was formed by Pd(0)-catalysed coupling of an arylboronic acid (ring D) and a bromobenzoic ester (ring A). Rings C and D were linked by the Wittig reaction, while final ring closure was effected by tetraphenylethene assisted Wurtz reaction.

The synthesis of riccardin C

Abstract The macrocyclic bis(bibenzyl) riccardin C, isolated from Riccardia multifida was synthesized in an unambiguous way by Ni(O) assisted intramolecular aryl-aryl bond formation from a diiodobenzoate as the key step.

The synthesis of Garugamblin-1

Abstract The Z isomer of the title compound (21) and its regioisomer (22) were synthesized using an isoxazole synthon (17) for the elaboration of the β-methoxy-enone function. 21 and 20 spontaneously isomerized to the E isomers i.e. to garugamblin-1 (1) and its regioisomer (22) resp.

Total syntheses of riccardins A, B, and C, cytotoxic macrocyclic bis(bibenzyls) from liverworts

Di-O-methylriccardin A (3), riccardin A (1), and riccardin B (4) were synthesized by convergent schemes. Rings A and D of both riccardin A and B, as well as rings B and C of riccardin B were joined by the Ullmann ether synthesis. The aryl-aryl bond in riccardin A was established by Ni(0)-assisted intramolecular coupling of a di-iodoester (17). Rings A and B were linked in all syntheses by the Wittig reaction, whereas ring closure was effected by a tetraphenylethene catalyzed Wurtz reaction. Demethylation of (3) gave riccardin C (2).

Chiroptical properties of acridino-18-crown-6 ligands and their complexes with chiral and achiral protonated primary (aralkyl) amine guest molecules.

This paper reports CD spectroscopic studies on acridino-18-crown-6 ligands (RR)-2 and 2a (see Figure 1), and their complexes with the enantiomers of alpha-naphthyl)ethylamine hydrogenperchlorate (1-NEA), 1-phenylethylamine hydrogenperchlorate (PEA) and alpha-2-naphthyl)ethylamine hydrogenperchlorate (2-NEA), and also with the achiral guests (1-naphthyl)methylamine hydrogenperchlorate (1-NMA), benzylamine hydrogenperchlorate (BA), methylamine hydrogenperchlorate (MA) and 1-methylnaphthalene (1-MN). The general feature of the CD spectra of complexes of (RR)-2 with MA, BA, (R)- and (S)-PEA is the replacement of the oppositely signed 1Bb doublet of the host by one positive band near 265 nm. The CD spectra of the heterochiral and homochiral complexes of phenazino and acridino hosts (R,R)-1, 1a, (R,R)-2 and 2a with (R)- and (S)-1-NEA and 1-NMA are governed by exciton interaction. Surprisingly, the heterochial [(R,R)/(S)] complexes of the structural isomeric 2-NEA gave rise to a positive couplet in contrast to the negative couplet measured in the spectrum of the heterochiral [(R,R)/(S)] complexes of 1-NEA.

The constitution of riccardin B

Abstract The constitution of riccardin B, a macrocyclic bis(bibenzyl) isolated from Riccardia multifida was established by the unambigous synthesis of its di- O -methyl ether.

Synthesis of some pterocarpenes obtained from Brya ebenus

The syntheses of bryacarpenes-1, -2, and -4, [4,10-dihydroxy-3,8,9-trimethoxy-(1), 10-hydroxy-3,8,9-trimethoxy-(2), and 4-hydroxy-3,9,10-trimethoxy-6H-benzofuro[3,2-c][1]benzopyran (3)], (±)-bryaflavan [(±)-3′,6,7-trihydroxy-2′,4′-dimethoxyisoflavan (33)], 4-hydroxy-3,7-dimethoxy-(18) and 3,7-dimethoxy-6H-benzofuro[3,2-c][1]benzopyran-9,10-quinone (19) is described. The quinones are not identical with bryaquinone and deoxybryaquinone, for which structures (18) and (19) had been proposed previously. In the syntheses of the pterocarpenes the novel reduction of isoflavones to isoflavan-4-ones by di-isobutylaluminium hydride was used.