Synthesis and chiroptical properties of amphiphilic dendrimers based on 2,3-dihydroxybenzyl alcohol

The syntheses and chiroptical properties of amphiphilic dendrimers based on 2,3-dihydroxybenzyl alcohol up to the third generation are described. Wate r-solubility is imparted to the dendrimers using a selective palladium-cata lyzed deprotection of allyl ester terminal groups. Circular dichroism studi es indicate that a transfer of chirality from the central core to the achir al branch segments does not occur in any of the dendrimers in THF. However, a temperature-dependent Cotton effect associated with the 2,3-dialkoxybenz yl ether branching subunit appears at the first generation in water consist ent with a transfer of chirality from the chiral core to the dendrons. This effect disappears at the second and third generations suggesting greater c onformational flexibility at higher dendrimer generation. The increased fle xibility at higher dendrimer generation is rationalized by a decrease in hy drophobic compression at higher dendrimer generation. This work highlights the effect of asymmetric branching and solvent-induced compression in restr icting the conformational mobility of dendrimers. (C) 2001 Elsevier Science Ltd. All rights reserved.