title: Pyrone Diels-Alder Routes to Indolines and Hydroindolines: Syntheses of Gracilamine, Mesembrine, and Δ(7) -Mesembrenone.
abstract: Although the Diels-Alder reaction has long been utilized for the preparation of numerous heterocycles, opportunities to extend its power remain. Herein, we detail a simple, modular, and robust approach that combines various amines regioselectively with 4,6-dichloropyrone to create substrates which, under appropriate conditions, can directly deliver varied indolines and hydroindolines through [4+2] cycloadditions with substitution patterns difficult to access otherwise. As an initial demonstration of the power of the strategy, several different natural products have been obtained either formally or by direct total synthesis, with efforts toward one of these-the complex amaryllidaceae alkaloid gracilamine-affording the shortest route to date in terms of linear step count.
authors: Dept. of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL, 33458, USA.
authors: Pei
authors: P
authors: Gan
authors: Dept. of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA.|Dept. of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL, 33458, USA.
authors: Myles W
authors: MW
authors: Smith
authors: Dept. of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA.
authors: Nathaniel R
authors: NR
authors: Braffman
authors: Dept. of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA. sasnyder@uchicago.edu.|Dept. of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL, 33458, USA. sasnyder@uchicago.edu.|Dept. of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL, 60637, USA. sasnyder@uchicago.edu.
authors: Scott A
authors: http://orcid.org/0000-0003-3594-8769
authors: SA
authors: Snyder
keywords: Diels-Alder reaction; alkaloids; cascade reaction; natural products; total synthesis