Synthesis of phantasmidine.

Reaction of 6-chloro-2-fluoro-3-pyridineacetamide with 1,2-bis(trimethylsilyloxy)cyclobutene in ether saturated with hydrogen chloride afforded the keto amide in 85% yield. In the key step, treatment of the keto amide with aqueous KOH in t-BuOH resulted in a tandem intramolecular aldol reaction-intramolecular nucleophilic aromatic substitution sequence to give the tetracylic lactam in 46% yield. Reduction of the lactam with BH(3) in THF gave phantasmidine in 67% yield.