Synthesis and chiroptical properties of dendrimers elaborated from a chiral, nonracemic central core

Three generations of ester-terminated dendrimers have been constructed from (1R,2S)-2-aminol-phenyl- 1,3 -propanediol, 1, as the central core. The chiroptical properties of the dendrimers were measured revealing that the molar rotations [Phi] of the dendrimers decreased with increasing dendrimer generation. Comparison to a series of substituted benzoate derivatives of 1 suggested that the decrease in rotation was a consequence of a steric effect upon the conformational equilibrium of the central core that increased with increasing dendrimer generation. The optical rotations of dendrimers 7-9 were also observed to be solvent and temperature dependent.