Our current research is directed at elucidation of three-dimensional molecular structures of selected organic compounds in the solution and/or a solid-state by means of chiroptical methods, electronic and vibrational circular dichroism (ECD/VCD) in particular. Our synthetic activity is directed at the synthesis and transformations of natural products related to β-lactam antibiotic analogues, terpenoids and steroids. Currently we are focusing on the structure-chiroptical properties' relationship of: classical and non-classical β-lactam analogues; carba- and oxaanalogues of penicillins and cephalosporins; cisoid enons; vitamin E and analogues; cyclic sulfites; steroidal nitro alcohols; thiiranes; certain active pharmaceutical ingredients (API's). A special attention is devoted to the stereostructure determination of transparent molecules. To fulfill the requirements of electronic circular dichroism spectroscopy (ECD), a chiral, nonracemic but transparent substance has to be transformed into a chromophoric derivative. For this purpose, a methodology was developed which uses various complexes with two transition metal atoms linked together by a single or multiple bond of general formula M2(OCOR)4, with M = Mo, Rh, Ru or Re and R = CH3, CF3, etc. These achiral complexes act as auxiliary chromophores. After the exchange of achiral ligands of the stock complex for different types of chiral ligands, e.g., amino acids, glycols, aminols, diamines, alcohols, amines, etc., the optically active complexes are formed. ECD of these complexes can easily be measured and used for the correlation between signs of Cotton effects (CEs) obtained and the structure of investigated compounds. In our Laboratory we use very effectively the High Performance Liquid Chromatography with coupled on–line ECD/UV-VIS detection (HPLC-ECD) to perform separations and purifications of variety of samples, such as pharmacologically active compounds. The ECD detector provides valuable information since it responds only to optically active compounds. On-line ECD opens a new avenue in chiroptical spectroscopy and structural chemistry. In fact, it makes possible to record a ECD spectrum of a product even in a rather complex matrices. HPLC-ECD has a higher selectivity and a stable signal which is not affected by gradient analysis, unlike the HPLC-UV, due to the fact that only chiral compounds are sensed using ECD detection. This also implies that less interference will occur. Therefore HPLC-ECD can be a good alternative to commonly used HPLC-UV when interference of matrix compounds is observed in the UV chromatogram. For the interpretation of the ECD spectra measured on-line, quantum chemical calculations are performed/recommended.   Our focus is also directed at the application of solid state CD spectroscopy to structural studies. In the solid state, achiral molecules with some degree of restricted freedom, such as rotation and orientation about chemical bonds, may become optically active and thus can be studied by means of CD. Reprinted by permission of: Maria J. Milewska and T. Połoński. (M. Szyrszyng, E. Nowak, M. Gdaniec, Maria J. Milewska, T. Połonski, Tetrahedron: Asymm. 2004, 15, 103-107). Synthesis and transformations of natural products related to terpenoids and steroids are also in the field of our group's interest. Total synthesis of tricyclic diterpenoids of microbiological origin, such as cycloareneosene and guanacastepene A as well as 1α,25-dihydroxyvitamin D3 is carried on. An emphasis is given to transformations potentially useful as new general synthetic methods. The experimental measurements are combined with corresponding quantum mechanical computational predictions to establish, if possible, the absolute configuration and/or determine the predominant conformations of chiral molecules in the solution phase.