Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• pronucleophile to a substituted furanyl nitroolefin catalysed by a bifunctional cinchonine-derived thiourea has been used as the key stereocontrolling step in a new synthetic strategy to the heavily functionalised piperidine core of keramaphidin B. Keywords: bifunctional organocatalyst; enantioselective Michael

• addition; keramaphidin B; nitro-Mannich lactamisation cascade; Introduction Keramaphidin B (1) is a marine alkaloid first isolated by Kobayashi in 1994 from the Okinawan marine sponge Amphimedon sp and has been shown to be cytotoxic against KB human epidermoid carcinoma cells (IC50 0.28 μg/mL) and P388

• , in their landmark paper entitled ‘On the Biosynthesis of Manzamines’ postulated that keramaphidin B was a common intermediate in the biosynthesis of the manzamine alkaloids [2]. Several years later, Baldwin and co-workers synthesised keramaphidin B following a biomimetic pathway via an intramolecular