A novel route towards cycle-tail peptides using oxime resin: teaching an old dog a new trick.

Two anabaenopeptins, Schizopeptin 791 and anabaenopeptin NZ825, have similar structural features and have been synthesized via a novel acid-catalyzed head-to-side-chain concomitant cyclization/cleavage reaction on oxime resin. The methodology gave rapid access to the anabaenopeptin scaffold by taking advantage of a combined solid-phase/solution-phase synthetic strategy. Also, as side-products of the synthesis, large C2-symmetric 38-member cyclic peptides ring bearing two endocyclic lysine side-chains were isolated, constituting a novel cyclic peptide scaffold.