PREPARATION AND STRUCTURE-CHIROPTICAL RELATIONSHIPS OF TARTARIC ACID-BASED LAYER-BLOCK CHIRAL DENDRIMERS

Two optically active, diastereoisomeric, first generation layer-block dendrimers 1 and 2 have been prepared by a convergent synthetic proced ure. These chiral, layer-block dendrimers utilize 4-tert-butylphenoxy moieties as the surface groups and phloroglucinol as the branching jun ctures. Two different chiral units, which are derivatives of (D)- and (L)-tartaric acid, serve as the chiral linkers between the surface gro up and the branching juncture, or between two branching junctures. The first layer-block dendrimer 1 has an outer chiral layer made up of si x (L)-tartrate derived units and an inner chiral layer of three (D)-ta rtrate derived units. The second layer-block dendrimer 2 has an outer shell consisting of three (D)- and three (L)-chiral units and an inner shell of three (D)-chiral units. The molar rotation of these structur ally flexible, low generation dendritic compounds is proportional to t he number of chiral tartrate units in excess, with the chiroptical eff ect of a (D)-tartrate derived chiral unit cancelling that of an (L)-ta rtrate derived unit on a 1:1 basis. Circular dichroism studies, howeve r, reveal that this cancellation effect is more effective when both th e (D)- and (L)-chirons are situated within the same layer.