Péter Nemes

Chemistry of nitroenamines. Synthesis of pyrrolizine derivatives

2-Nitromethylene-pyrrolidine (1) readily reacts with di- and tricarbonyl compounds resulting in addition products (4a-d), which could be cyclized to substituted dihydro-1H-pyrrolizines easily (8a-e).

Substituent and solvent dependent conformations of some saturated diazatricyclic compounds

Abstract The double Mannich condensation of 2-quinolizidone with formaldehyde and methyl amine resulted in the 11-methyl-7,11-diazatricyclo[7.3.1.0 2,7 ]tridecan-13-one of endo -type selectively. The stereochemistry, isomerism and conformational behaviour of derivatives obtained by reduction at C-13 were investigated extensively by one- and two-dimensional 1 H , 13 C and 15 N NMR spectroscopy. The site of the protonation and its effect on the conformational equilibria and chemical shifts were also revealed.

OCCURRENCE OF TOXIN PRODUCING CYANOBACTERIA IN HUNGARY. ISOLATION, SEPARATION AND IDENTIFICATION OF MICROCYSTINS

Cyanobacteria (blue-green algae), Microcystis aeruginosa sp., were isolated from a massive bloom in a eutrophic waterbody in Hungary. Their toxic effect, determined by a mouse test, was associated with the occurrence of microcystins YR and LR which were isolated, separated by means of HPLC procedures and identified by mass spectroscopy. The toxin content of the dry cell material is about 0.22 %, indicating a pronounced toxin-producing ability of the species investigated

Mannich condensations of activated cyclic enamines

Abstract The synthesis of Mannich compounds starting from activated enamines, i.e., 2-nitromethylene-pyrrolidine and pyrrolidin-2-ylidene-acetic acid ethyl ester, with various amines and formaldehyde or ethyl glyoxylate are described. In order to furnish new Mannich type molecules and to improve the yields sequential reaction routes and 1,2,3-benzotriazole-substituted adducts as reactants were also tested. Additionally, the steric structure of a tricyclic spiro compound formed unexpectedly in high yield was elucidated in details by modern NMR methods. Graphical Abstract