Dragana Milić

Liquid-crystalline fullerene–ferrocene dyads

The 1,3-dipolar cycloaddition reaction was used to assemble fullerene, ferrocene and a second-generation liquid-crystalline cyanobiphenyl-based dendrimer. The targeted compound displayed an enantiotropic smectic A phase from 40 to 135 °C. The d-layer spacing was determined by X-ray diffraction, and was found to be independent of temperature with a value of 95 A. Molecular modeling and structural considerations suggested partial bilayer organization of the mesogenic molecular units within the smectic layers. Oxidation or reduction processes of the basic components (ferrocene, fullerene, dendrimer) were investigated by electrochemical techniques, and were in agreement with the structure. Photoinduced electron transfer from ferrocene to fullerene was identified, most likely with a “through space” mechanism.

The synthesis and biological evaluation of A-ring substituted steroidal p-quinones

Abstract The preparation of A-ring steroidal 1,4-quinones involves m -CPBA/(BzO) 2 O/ hv oxidation of estrone (or estradiol 17-acetate), acid rearrangement of the obtained quinol, and oxidation. A detailed NMR analysis of 1,4-quinones and their derivatives, as well as the results of preliminary antibacterial and cytotoxicity tests is presented.

Photophysical, electrochemical, and mesomorphic properties of a liquid-crystalline (60)fullerene-peralkylated ferrocene dyad

Two fullerene–peralkylated ferrocene derivatives were synthesized: (1) a liquid-crystalline dyad (compound 1) was obtained by introduction of nonamethyl ferrocene into a liquid-crystalline fullerene derivative and (2) a reference compound (compound 2) was synthesized by attachment of nonamethyl ferrocene to a fulleropyrrolidine. The liquid-crystalline dyad displayed an enantiotropic smectic A phase from 57 to 155 °C. Oxidation and reduction processes were investigated by cyclic voltammetry, and were in agreement with the electrochemical characteristics of the redox-active units (peralkylated ferrocene, fullerene, dendrimer). Photoinduced electron transfer from ferrocene derivative to fullerene was identified.

A NOVEL M-CPBA OXIDATION : P-QUINOLS AND EPOXYQUINOLS FROM PHENOLS

Abstract Steroidal quinols were obtained on large scale in 50–70% yield, together with syn -epoxyquinols. The reaction conditions can be adjusted to afford only the corresponding steroidal epoxyquinol in 51–54% yield.

Oxidation of steroidal 5-en-3β-ols with Jones reagent in ether

The two-phase oxidation of steroidal 5-en-3 beta-ol (via 5-en-3-ones) into corresponding 4-en-3,6-diones in diethyl ether with Jones reagent was investigated. It was found that the system Jones reagent/diethyl ether enables short reaction times and easy isolation of the obtained products. The exclusive abstraction of 4 alpha-hydrogen during oxidation, together with molecular mechanics (MM2), and semiempirical (PM3) calculations, suggest that boat conformation of ring A precedes the formation of corresponding radicals (or cations).

NaY Zeolite: A Useful Catalyst for Nitrile Hydrolysis

The NaY zeolite catalysed hydrolysis of nitriles to primary amides is reported. It is found that aryl nitriles with strong electron-withdrawing substituents and cyanopyridines are readily hydrolysed in the water suspension, while aliphatic nitriles do not react.

A dendritic fullerene-porphyrin dyad.

We describe the synthesis, characterization and photophysical properties of a fullerene derivative whose structure includes a Zn-porphyrin and a second generation liquid-crystalline (LC) dendrimer. The size of the fullerene and porphyrin units with respect to the size of the LC dendrimer prevents the formation of liquid-crystalline phases. However, this system gives interesting photoinduced electron transfer phenomena. Compound has been investigated by steady state and time resolved fluorescence as well as transient absorption spectroscopy in polar and apolar solvents. We demonstrate that the fluorescence of the porphyrin unit in is quenched compared to the Zn-tetraphenylporphyrin used as reference. Femto- and picosecond transient absorption permit to identify the formation of a radical ion pair while nanosecond experiments allowed the determination of the charge recombination lifetimes.

Synthesis and antiproliferative activity of epoxy and bromo compounds derived from estrone.

Based on biological properties of epoxyquinols from natural sources, bromo and epoxyquinols derived from estrone were synthesized and screened against Fem-X, HeLa and K(562) cell lines. Evidence was found that the bromine atom and the epoxy moiety significantly increase the antiproliferative activity within the series.

Structure-retention relationship study of polyoxygenated steroids.

The chromatographic behavior of 31 newly synthesized polyoxygenated steroids was investigated by the means of reversed-phase planar chromatography. Retention data were correlated to molecular characteristics of the analytes with view to examine possible relationships by the means of multiple linear regression (MLR) and partial least square (PLS) regression. On the basis of comparison of the statistical parameters obtained for both MLR and PLS models, descriptors best describing the analyte behavior were selected. Statistically significant and physically meaningful structure-retention relationships were obtained. Calculated lipophilicity expressed as XlogP as well surface tension and Hansen hydrogen bonding was included in both MLR and PLS models.

Estrone derived steroidal diepoxide: biologically active compound and precursor of a stable steroidal A,B-spiro system.

A simple approach to a stable steroidal estrone derived A,B-spiro system is reported. Treatment of estrone derived A-ring diepoxyalcohol with the Ac(2)O-TMSOTf system at the ambient temperature led to acetylation, while at the reflux temperature the acid-catalysed rearrangement took place affording the spiro-compound. Results of extensive in vitro and in vivo anticancer tests on the diepoxide, as well as preliminary data on the antiproliferative activity of the spiro-product against three cancer cell lines, are also presented.