Synthetic studies toward C-1027 chromophore: construction of a highly unsaturated macrocycle

Treasures old and new: what we can learn regarding the macrocyclic problem from past and present efforts in natural product total synthesis

In this review the strategies leading to successful macrocyclization, in the context of total synthesis are discussed.

Total synthesis and related studies of large, strained, and bioactive natural products

Our chemical syntheses and related scientific investigations of natural products with complex architectures and powerful biological activities are described, focusing on the very large 3 nm-long polycyclic ethers called the ciguatoxins, highly strained and labile chromoprotein antitumor antibiotics featuring nine-membered enediyne cores, and extremely potent anthelmintic macrolides called the avermectins.

Total synthesis of the bicyclic depsipeptide HDAC inhibitors spiruchostatins A and B, 5''-epi-spiruchostatin B, FK228 (FR901228) and preliminary evaluation of their biological activity

The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors spiruchostatins A and B, 5''-epi-spiruchostatin B and FK228 were efficiently synthesized in a convergent and unified manner. The synthetic method involved the following crucial steps: i) a Julia-Kocienski olefination of a 1,3-propanediol-derived sulfone and a L- or D-malic acid-derived aldehyde to access the most synthetically challenging unit, (3S or 3R,4E)-3-hydroxy-7-mercaptohept-4-enoic acid, present in a D-alanine- or D-valine-containing segment; ii) a condensation of a D-valine-D-cysteine- or D-allo-isoleucine-D-cysteine-containing segment with a D-alanine- or D-valine-containing segment to directly assemble the corresponding seco-acids; and iii) a macrocyclization of a seco-acid using the Shiina method or the Mitsunobu method to construct the requisite 15- or 16-membered macrolactone. The present synthesis has established the C5'' stereochemistry of spiruchostatin B. In addition, HDAC inhibitory assay and the cell-growth inhibition analysis of the synthesized depsipeptides determined the order of their potency and revealed some novel aspects of structure-activity relationships. It was also found that unnatural 5''-epi-spiruchostatin B shows extremely high selectivity (ca. 1600-fold) for class I HDAC1 (IC(50)=2.4 nM) over class II HDAC6 (IC(50)=3900 nM) with potent cell-growth-inhibitory activity at nanomolar levels of IC(50) values.