Studies Directed towards the Synthesis of the Acridone Family of Natural Products: Total Synthesis of Acronycines and Atalaphyllidines

A modular
and flexible
three-step synthetic strategy has been developed
for the synthesis of acridone natural products of biological significance.
The tetracyclic core of acridone derivatives has been achieved efficiently
in high yield from commercially available anthranilic acid and phenol
derivatives via condensation reaction, followed by regioselective
annulation. Acridone alkaloids acronycine and noracronycine are synthesized
in improved overall yields in fewer steps than the previously reported
approaches. The method has further been used for the synthesis of
atalaphyllidine and 5-hydroxynoracronycine in excellent yields for
the first time. Moreover, the synthetic utility of the present strategy
has been showcased by the synthesis of oxa and thia analogues of acronycine
alkaloid.