Synthesis and chiroptical analysis of optically active chiral shell dendrons

We have prepared a series of chiral dendrons (1-4) in which chiral subunits are placed in individual generational shells at varying distances from the focal point. The optical activity of these chiral dendritic structures is successfully modeled using structurally similar low-molecular weight model compounds. In dendrons 1a and 1b a chiral subunit is directly adjacent to t he focal point, whereas in dendrons 2, 3, and 4a,b the chiral subunits are incorporated in the interior of the dendron. A marked difference in optical activity between the former (1a and 1b) and latter (2, 3, 4a,b) dendrons i s mirrored in the optical activities of model compounds 12a, 12b, 19a, and 19b. These model compounds directly mimic the surrounding constitution of t he chiral subunits in the dendrons. This successful analysis of the chiropt ical data using low-molecular weight model compounds suggests that these de ndrons do not possess conformational order in solution.