Synthesis and chiroptical properties of layer-block dendrimers

A series of optically active, tartaric acid-based, monodisperse dendrimers 1 - 4 was prepared. The central core and branching junctures of these dendritic compounds were made up from phloroglucinol units and the surface sectors used were 4-tert-butylphenoxy moieties. The optically active elements, which were derivatives of either (D)- or (L)-tartaric acid, served as the chiral linker branches of these dendrimers. For this series of structurally flexible, low generation optically active dendrimers, the observed molar optical rotation was proportional to the number of chiral units residing within the dendritic matrix, with the chiroptical property of the (D)-tartrate unit cancelling that of the (L)-tartrate unit on a one to one mole asis. Circular dichroism studies, however, revealed that this cancellation effect was more effective when both the (D)- and (L)-chirons were situated within the same layer.