Enantioselective synthesis of N1999A2

J Am Chem Soc. 2006 Nov 22;128(46):14825-7. doi: 10.1021/ja0662467.

Abstract

An enantioselective synthetic route to the enediyne antibiotic N1999A2 (1) is described, proceeding in 21 steps (0.4% yield, 77% average yield per step) from (R)-(+)-glycidol. The route involves the convergent assembly of three components: a (1-iodovinyl) stannane (2), a 1,5-hexadiyne-3,4-diol derivative (3), and a substituted naphthoic acid (4). Important transformations in the synthetic sequence include the palladium-catalyzed coupling of 2 and 3, an intramolecular oxidative cyclization of a terminal bisacetylene, and a transannular anionic (bi)cyclization of a cyclic bromoenetriyne. The careful selection and manipulation of protective groups throughout the sequence proved to be critical to the development of the synthetic route, where all late-stage intermediates were unstable and could not be concentrated. In the final step of the sequence, three protective groups were removed in a single operation, providing synthetic N1999A2 (1) in 76% yield. Conditions were found that, for the first time, led to the precipitation of 1 as a solid.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Enediynes / chemical synthesis*
  • Enediynes / chemistry
  • Epoxy Compounds / chemical synthesis*
  • Epoxy Compounds / chemistry
  • Humans
  • Naphthalenes / chemical synthesis*
  • Naphthalenes / chemistry
  • Stereoisomerism

Substances

  • Enediynes
  • Epoxy Compounds
  • N1999-A2
  • Naphthalenes