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Protected Newkome-type second-generation dendrimers (based on Lin's amine) were synthesized with a pyrene moiety attached to the core. The photophysical property in aqueous solution of the protected dendrimers shows self-association behavior in water. Pyrene excimer emission at 475 nm is observed in water even at very low concentrations of protected dendrimer (ca. 5 × 10-8 M). This emission band is absent in other solvents even up to a concentration of 10-5 M. The corresponding unprotected dendrimer does not show the pyrene excimer fluorescence. The amide of pyrene butyric acid with tert-butylamine shows the formation of excimer, albeit with very low intensity. Quenching studies on the dendrimer with hydrophilic quencher iodide anion (I-) reveal that there is significant quenching of fluorescence intensity in the case of N-tert-butyl-4-pyren-1-ylbutyramide as compared to that of the pyrene-attached second-generation protected dendrimer. This shows that the pyrene moiety in the case of the protected dendrimer is significantly shielded from the surrounding.

Conversion of Azides to N-(tert-Butoxycarbonyl)amines. -The title method using Lindlar catalyst under hydrogen atmosphere, in the presence of Boc 2 O, is exceptionally chemoselective. Various azides are converted into the corresponding N-Boc-protected amines without affecting functional groups, which are known to be sensitive toward catalytic hydrogenation conditions. -(REDDY, P. G.; PRATAP, T. V.; KUMAR, G. D. K.; MOHANTY, S. K.; BASKARAN*, S.; Eur.