Syntheses and cytotoxicity of syringolin B-based proteasome inhibitors

The concise and modular total synthesis of the bacterial natural product and irreversible proteasome inhibitor syringolin B has been achieved. This synthesis has enabled the ready preparation of three diverse, structurally modified syringolin derivatives. The actions of these compounds in inhibiting the proliferation of neuroblastoma cell lines was evaluated, and significant enhancements in potency compared to the natural product were realized.