A novel tin-mediated indole synthesis and its application to natural product synthesis

A new indole synthesis is described. The key step involves a novel tin-mediated free radical reaction to generate unstable 2-tri-n-butylstannyl-3-substituted indoles, which upon mild acidic workup, furnishes 3-substituted indoles. The 2-tri-n-butylstannyl-3-substituted indoles are also subjected to a one-pot Stille coupling to provide 2,3-disubstituted indoles. Two applications of the above methodology are also described. The efficient total synthesis of (${\pm})$-vincadifformine involves the construction of the indole skeleton by using this indole formation reaction and a novel amine protection-deprotection procedure as crucial steps. A new synthetic approach is explored towards the total synthesis of antitumor agent discorhabdin C. The key step towards the key intermediate has greatly contributed to the development of the novel indole synthesis methodology