A second-generation total synthesis of (+)-discodermolide: the development of a practical route using solely substrate-based stereocontrol

J Org Chem. 2005 Jan 7;70(1):150-60. doi: 10.1021/jo048534w.

Abstract

A novel total synthesis of the complex polyketide (+)-discodermolide, a promising anticancer agent of sponge origin, has been completed in 7.8% overall yield over 24 linear steps, with 35 steps altogether. This second-generation approach was designed to rely solely on substrate control for introduction of the required stereochemistry, eliminating the use of all chiral reagents or auxiliaries. The common 1,2-anti-2,3-syn stereotriad found in each of three subunits, aldehyde 9 (C(1)-C(5)), ester 40 (C(9)-C(16)), and aldehyde 13 (C(17)-C(24)), was established via a boron-mediated aldol reaction of ethyl ketone 15 and formaldehyde, followed by hydroxyl-directed reduction to give 1,3-diol 14. Alternatively, a surrogate aldehyde 22 was employed for formaldehyde in this aldol reaction, leading to the beta-hydroxy aldehyde 20 as a common building block, corresponding to the discodermolide stereotriad. Key fragment unions were achieved by a lithium-mediated anti aldol reaction of ester 40 and aldehyde 13 under Felkin-Anh control to provide (16S,17S)-adduct 51 and a boron-mediated aldol reaction between enone 10 and aldehyde 9, exploiting unprecedented remote 1,6-stereoinduction, to give the (5S)-adduct 57.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkanes / chemical synthesis*
  • Alkanes / chemistry
  • Alkanes / pharmacology
  • Animals
  • Antineoplastic Agents / chemical synthesis*
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology
  • Carbamates / chemical synthesis*
  • Carbamates / chemistry
  • Carbamates / pharmacology
  • Combinatorial Chemistry Techniques
  • Indicators and Reagents
  • Lactones / chemical synthesis*
  • Lactones / chemistry
  • Lactones / pharmacology
  • Molecular Structure
  • Porifera / chemistry*
  • Pyrones
  • Stereoisomerism

Substances

  • Alkanes
  • Antineoplastic Agents
  • Carbamates
  • Indicators and Reagents
  • Lactones
  • Pyrones
  • discodermolide