Cyclic Disulfides as Functional Mimics of the Histone Deacetylase Inhibitor FK-228

Efficient preparation of unsymmetrical disulfides by nickel-catalyzed reductive coupling strategy

Disulfides are widely found in natural products and find a wide range of applications in life sciences, materials chemistry and other fields. The preparation of disulfides mainly rely on oxidative couplings of two sulfur containing compounds. This strategy has many side reactions and other shortcomings. Herein, we describe the reductive nickel-catalyzed cross-electrophile coupling of unactivated alkyl bromides with symmetrical alkyl- and aryltetrasulfides to form alkyl-alkyl and aryl-alkyl unsymmetrical disulfides. This approach for disulfide synthesis is practical, relies on easily available, unfunctionalized substrates, and is scalable. We investigated the mechanism of this transformation and found that the tetrasulfide compound does not selectively break the central S–S bond, but regio-selectively generates trisulfide intermediates.

The preparation of disulfides mainly relies on oxidative couplings of two sulfur-containing compounds, a strategy which has side reactions and other shortcomings. In this work, the authors present a reductive nickel-catalyzed cross-electrophile coupling of unactivated alkyl bromides with symmetrical tetrasulfides to form unsymmetrical disulfides, proceeding via trisulfide intermediates.

Disulfide-bridged peptide macrobicycles from nature

This review highlights known disulfide-bridged peptide bicycles and the studies on their unique structural and biological features.

Romidepsin (Istodax, NSC 630176, FR901228, FK228, depsipeptide): a natural product recently approved for cutaneous T-cell lymphoma

Romidepsin (Istodax), a selective inhibitor of histone deacetylases (HDACs), was approved for the treatment of cutaneous T-cell lymphoma in November 2009 by the US Food and Drug Administration. This unique natural product was discovered from cultures of Chromobacterium violaceum, a Gram-negative bacterium isolated from a Japanese soil sample. This bicyclic compound acts as a prodrug, its disulfide bridge being reduced by glutathione on uptake into the cell, allowing the free thiol groups to interact with Zn ions in the active site of class I and II HDAC enzymes. Due to the synthetic complexity of the compound, as well as the low yield from the producing organism, analogs are sought to create synthetically accessible alternatives. As a T-cell lymphoma drug, romidepsin offers a valuable new treatment for diseases with few effective therapies.