Aryne Chemistry of Podocarpic Acid Derivatives

Abstract

The anthranilic acid (2), a key intermediate for the generation of an aryne at C13 of podocarpic acid derivatives, was synthesized from the 14-amino compound (5) which in turn was generated regiospecifically in high yield by treatment of the 13-bromo compound (25) with sodamide in liquid ammonia. The amine was converted into the anthranilic acid by two separate routes: firstly by directed lithiation and trapping of the lithium species with a CO₂ moiety, and secondly by oxidative cleavage of an isatin fused across positions 13 and 14.