Keywords: Nucleophilic vinylic substitution (S N V) mechanism / Enol ethers / Alkoxymethylene compounds / Quinoxalines / Molecular calculationsTreatment of 6-aminoquinoxaline with β,β-diactivated alkoxymethylene derivatives gave the corresponding N-(quinoxalin-6-yl)enamines. A variant of the S N V reaction mechanism was proposed for substitution of the alkoxymethylene compounds, on the basis of the structures of the precursor

Aroma and flavor profile of MD2 pineapple variety was investigated. Fruits imported from different geographical regions (Costa Rica, Puerto Rico) were labeled as an organic food. Characteristic volatile and non-volatile compounds obtained by hydro-distillation and direct percolation were identified and quantified by gas chromatography-mass spectroscopy (GC/MS). At least 22 components in percolated extract (or 17 in distillate) were detected according to their mass spectra and retention time. Relative concentration of identified substances varied from 547.7 to 1110.0 μg.kg-1. Analysis showed dominance of esters and furanone-derived compounds as major aroma constituents. Most abundant volatiles identified in all samples were methyl 2-methylbutanoate and methyl hexanoate. Relationships between volatile and non-volatile compounds were also studied.

In the course of study of epiphytic microorganisms occurring on the surface of roots of Taxus baccata L. a new strain Streptomyces sp. AC113 was isolated. According to 16S ribosomal DNA-based identification the new strain is 99% identical with Streptomyces flavidofuscus. This strain cultivated in an arginine glycerol medium produced three major metabolites identified as (-)-8-O -methyltetrangomycin (1), 8-O -methyltetrangulol (2) and 8-O -methyl-7-deoxo-7-hydroxytetrangomycin (3). The chemical structures of these angucyclines were elucidated by 1D and 2D NMR as well as by mass spectrometry. Isolated angucycline metabolites showed significant antimicrobial activity against Bacillus cereus and Listeria mocytogenes. Cytotoxic activities of compounds 1, 2 and 3 against four cell lines (B16, HT-29 and non - tumor V79, L929) were evaluated. Compound 3 was the most potent anticancer agents with IC(50) 0.054 microg/ml against cell line B16.

Diastereoselective reduction ThienoquinolizidinePhenanthroquinolizidine alkaloids a b s t r a c tThe stereoselective synthesis of epi-thieno analogues of the phenanthroquinolizidine bioactive alkaloids (À)-Cryptopleurine and (À)-(15R)-Hydroxycryptopleurine was achieved in five steps starting from easily available enantiopure (S)-2-aminoadipic acid used as chiral pool and nitrogen atom source. During these investigations, both p-cationic cyclization of chiral N-thienylmethyl-6-oxopipecolinic acids into pure (S)keto-lactams and theirs regioselective and diastereoselective reduction, considered as key steps of this sequence, were studied. Of particular interest, the FriedeleCrafts cyclization using (CF 3 CO) 2 O/BF 3 $Et 2 O show that near the expected keto-lactams, enamides and enamidones containing trifluoromethyl residue were isolated. A mechanism leading to the latter products with high synthetic potential was discussed.

Abstract:The synthesis of three new substituted 4-hetereoaryl-4-oxobut-2-enoic acids with indole ring substitutedin positions 3-, 5-and 7-is described. The addition of these Michael acceptors to 4-(1-phenylsulphonylpyrrol-3-yl)-4-oxobut-2-enoic acid in conjugate addition was explored using both racemic and chiral amines. In tandem with the crystallization-induced asymmetric transformation (CIAT) protocol the effective methodology for the synthesis of enantiomerically highly enriched substituted 2-amino-4-heteroaryl-4-oxobutanoic acids as multifunctional homotryptophan analogues was developed.