Total synthesis of the antitumor antibiotic (±)-streptonigrin: first- and second-generation routes for de novo pyridine formation using ring-closing metathesis

J Org Chem. 2013 Dec 20;78(24):12338-50. doi: 10.1021/jo402388f. Epub 2013 Dec 12.

Abstract

The total synthesis of (±)-streptonigrin, a potent tetracyclic aminoquinoline-5,8-dione antitumor antibiotic that reached phase II clinical trials in the 1970s, is described. Two routes to construct a key pentasubstituted pyridine fragment are depicted, both relying on ring-closing metathesis but differing in the substitution and complexity of the precursor to cyclization. Both routes are short and high yielding, with the second-generation approach ultimately furnishing (±)-streptonigrin in 14 linear steps and 11% overall yield from inexpensive ethyl glyoxalate. This synthesis will allow for the design and creation of druglike late-stage natural product analogues to address pharmacological limitations. Furthermore, assessment of a number of chiral ligands in a challenging asymmetric Suzuki-Miyaura cross-coupling reaction has enabled enantioenriched (up to 42% ee) synthetic streptonigrin intermediates to be prepared for the first time.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Antibiotics, Antineoplastic / chemical synthesis*
  • Antibiotics, Antineoplastic / chemistry
  • Cyclization
  • Molecular Structure
  • Stereoisomerism
  • Streptonigrin / chemical synthesis*
  • Streptonigrin / chemistry

Substances

  • Antibiotics, Antineoplastic
  • Streptonigrin