[reaction: see text] The aldol condensation of acetone with several isatins is described. The desired compound was obtained in quantitative yield and with good enantioselectivities up to 77%. The best results were obtained with 10 mol % H-D-Pro-L-beta3-hPhg-OBn as a catalyst, resulting in the preferential formation of the (R)-enantiomer. The absolute configuration of the newly formed chiral center has been assigned by an X-ray diffraction study and CD spectra analysis of the molecules.

A new strategy for the radiolabeling of porous nanocontainers has been developed, and the first experiments in vivo are reported. Our approach consists of the use of nanometer-sized zeolites whose channels have been filled with the positively charged gamma-emitter (111)In(3+) via simple ion exchange. To avoid leaching of the isotope under physiological conditions, the entrances of the channels have been closed using a specifically designed molecular stopcock. This stopcock has a positively charged group that enters the channels and entraps the loaded radionuclides via electrostatic and steric repulsion. The other side of the stopcock is a bulky triethoxysilane group that can covalently bind to the walls of the zeolite entrances, thereby irreversibly closing the channels. The surface of the zeolites has been functionalized with different chemical groups in order to investigate the different biodistributions depending of the nature of the functionalizations. Preliminary in vivo experiments with Wistar rats have been performed and showed the potential of the approach. This strategy leads to a nanoimaging probe with a very high density of radioisotopes in a confined space, which is highly stable in physiological solution and could allow a large variety of functionalities on its external surface.

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Three sets of oligomers containing the 4-carboxy-5-methyloxazolidin-2-one (Oxd) moiety have been synthesized with the aim of checking whether these molecules are able to fold in ordered structures: A set [Boc-(L-Ala-L-Oxd)(n)-OR], B set [Boc-(L-Ala-D-Oxd)(n)-OR], and C set [Boc-(Aib-L-Oxd)(n)-OR] preferential conformations have been analyzed with IR absorption, NMR, and CD. We have noticed that in these oligomers three stabilizing effects are active: (i) the rigid Oxd -CO-N(CH<)-CO- moiety, which always tend to assume a trans conformation; (ii) the formation of Oxd C=O...H-(alpha)C intramolecolar H-bonds; (iii) the alternate formation of 1 <-- 4 intramolecular C=O...H-N H-bonds. Through the analysis of the experimental data, we could demonstrate that only the oligomers of the B set are able to meet all three requirements listed above. By a deeper insight into the CD spectra, we gathered that the secondary structure adopted by the B set oligomers is a beta-bend ribbon spiral, which is a subtype of the 3(10)-helix.