Chiroptical properties of dendrimers with stereogenic end groups

The synthesis of dendrimers with stereogenic end groups 3S-[G(n)] and 3R-[G(n)] (n=1-4, 7), obtained from the condensation of (S)-(-)-alpha-methylbenzylamine, or (R)-(+)-alpha-methylbenzyl amine with aldehyde terminated dendrimers is described up to the seventh generation (up to 384 stereogenic groups). The chemiospecific reduction of the imine bonds thus created affords two new series of stereogenic dendrimers 4S-[G(n)] and 4R-[G(n)] (n=1-4). Then, the reaction with Ph2PCH2OH gives a series of stereogenic phosphino terminated dendrimers 5S-[G(n)] and 5R-[G(n)] (n=1-4). Studies of the chiroptical properties of all these non-hindered stereogenic dendrimers indicate that each terminal group behaves independently and that the specific rotation depends only on the number of stereogenic groups grafted on the dendrimer, whatever the generation is. (C) 1997 Published by Elsevier Science Ltd.