Total synthesis of burkholdacs A and B and 5,6,20-tri-epi-burkholdac A: HDAC inhibition and antiproliferative activity.

The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors burkholdacs A and B were efficiently synthesized in a highly convergent and unified manner. The synthesis features the amide coupling of a D-valine-D-cysteine- or D-allo-isoleucine-D-cysteine-containing segment with a D-methionine-containing segment to directly assemble the corresponding seco-acids, key precursors for macrolactonization. Using the same methodology, 5,6,20-tri-epi-burkholdac A was also synthesized.

Enantioselective total synthesis of dysidavarone A, a novel sesquiterpenoid quinone from the marine sponge Dysidea avara.

Dysidavarone A, a structurally unprecedented sesquiterpenoid quinone, was synthesized in 30 % overall yield in a longest liner sequence of 13 steps from commercially available o-vanillin. A highly strained and bridged eight-membered carbocyclic core was established by the C7-C21 carbon bond formation through a copper enolate mediated Michael addition to the internal quinone ring.

Total synthesis of bicyclic depsipeptides spiruchostatins C and D and investigation of their histone deacetylase inhibitory and antiproliferative activities.

The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors spiruchostatins C and D were synthesized for the first time in a highly convergent and unified manner. The method features the amide coupling of a D-leucine-D-cysteine- or D-valine-D-cysteine-containing segment with a D-alanine- or D-valine-containing segment to directly assemble the corresponding seco-acids, key precursors of macrolactonization. The HDAC inhibitory assay and cell-growth inhibition analysis of the synthesized depsipeptides determined the order of potency of spiruchostatins A-D in comparison with the clinically approved depsipeptide FK228 (romidepsin).