Studies towards the synthesis of diazonamide A. Synthesis of the indole bis-oxazole fragment

The indole bis-oxazole 2, a potential intermediate for the synthesis of the marine natural product diazonamide A 1, has been synthesised, and attempts to construct the model macrocycle (ring B) 3 are also described; in both approaches rhodium carbenoid N–H insertion reactions are used in key steps.