In the period 1999-2003 the following research topics were studied: 1. Syntheses of new reagents on the basis of propenoates, enaminones and related compounds for the synthesis of various heterocyclic, especially biologically significant, systems and heterocyclic amino acids. The syntheses of fused azirines, pyrroles and fused pyrroles, isoxazoles, pyrazoles, imidazoles, 1,2,4-triazoles, 1,2,4-oksadiazoles, pyranones and fused pyranones, pyridines and fused pyridines, pyridazines, pyrimidines and fused pyrimidines, oxazolo(4,5-c)quinolines and others werre developed. 2. "Ring-switching" methodology for the synthesis of chiral, enantiomerically pure heterocyclic amino acids, such as 3-heteroarylalanines, 3-heteroarylalaninols, 3-heteroaryllactic acid, 3-heteroarylpropan-1,2-diols and analogs was developed 3. These two methodologies were applied for the synthesis of some natural products, such as alkaloids of aplysinopsin, tioaplysinopsin, and carboline types and analogs. 4. Stereoselective and regioselective 1,3-dipolar cycloadditions of diazoalkanes, azomethine imines, nitrile oxides and others to the unsaturated bonds of propenoates were studies. Stereoselective amination of 5-substituted lactones and lactams gave the corresponding 5-substituted (3S,5S)-3-acetylaminotetrahidrofuran-2-ones and (3S,5S)-3-acetylaminopyrrolidin-2-ones. 5. Ring transformations of derivatives of heterocyclic systems via diazo and azido derivatives or intermediates were studied. By nitrosation of 1-substittued 3-amino-4H-quinolizin-4-ones the corresponding diazonium salts are formed, which gave by heating in an alcohol mixtures of unsubstituted quinolizine derivative and alkyl indolizine-3-carboxylates. The ratio between these two types of products is dependent on the alcohol used in this transformation. The reactions represents the first examples of Wolff's rearrangement of diazo amides and diazo esters. Results are described in the original papers and in some review articles. Review articles: 1. B. Stanovnik, J. Svete:Targets in Heterocyclic Systems, Vol. 4, 105-137 (2000). 2. B. Stanovnik, J. Svete: Synlett (Account) 2000, 1077-1093. 3. B. Stanovnik, J. Svete: Pyrazoles, Science of Synthesis, Houben-Weyl Methods of Molecular Transformations, Vol. 12, Georg Thieme Verlag, Stuttgart 2002, pp. 15-225. 4. B. Stanovnik: J. Heterocycl. Chem. 36, 1581-1593 (1999). 5. J. Svete: J. Heterocycl. Chem., 39, 437-454 (2002). 6. J. Svete: Monatsh. Chem. 135, 629-646 (2004). 6. B. Stanovnik, J. Svete: Chem. Rev. 104, 2433-2480 (2004). Plenary, section and other invited lectures: 18 plenary and 8 invited lectures on internatioanl congresses, symposia and other universities. For original papers for the period 1999-2003 see: SICRIS