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Paper | Regular issue | Vol 85, No. 12, 2012, pp.2949-2976
Published online, 29th October, 2012
DOI: 10.3987/COM-12-12597
A Total Synthesis of Herboxidiene Methyl Ester

Rajaratnam Premraj, Malcolm D. McLeod, Gregory W. Simpson, and Martin G. Banwell*

*Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia

Abstract

The total synthesis of the methyl ester, 35, of herboxidiene (1, a.k.a. GEX1A and TAN-1609), a polyketide displaying both herbicidal and anti-tumor activity, is described. The convergent reaction sequence involves, in its closing stages, the union of the phosphine oxide 3 with the aldehyde 21 to deliver, via a Horner–Wittig reaction with accompanying epimerization at C12, compound 33 that after deprotection affords an alcohol, 34, capable of participating in a regio- and diastereo-selective epoxidation reaction to give target 35. Phosphine oxide 3 was prepared via the intramolecular hetero-Michael addition of a secondary alcohol to a tethered and Z-configured acrylate while aldehyde 21 was generated, in the crucial step of the relevant reaction sequence, via an Ireland–Claisen rearrangement reaction.