Asymmetric Garratt–Braverman Cyclization: A Route to Axially Chiral Aryl Naphthalene–Amino Acid Hybrids

We report the first example of a
highly diastereoselective Garratt–Braverman
cyclization leading to the synthesis of chiral aryl naphthalene–amino
acid hybrids in excellent yields. The stereogenecity in the amino
acid has induced high diastereoselectivity for the reaction. Computations
based on density functional theory indicated a lower activation free
energy barrier for the M isomer as compared to that for
the P diastereomer (ΔΔG =
3.48 kcal/mol). Comparison of the recorded CD spectrum of the product
with the calculated one also supported the preferential formation
of the M diastereomer.