Prins-type macrocyclizations as an efficient ring-closing strategy in natural product synthesis

Prins-type macrocyclizations have recently emerged as a successful strategy in the synthesis of polyketide-derived natural products. This reaction provides a concise and selective means to form tetrahydropyran-containing macrocyclic rings of varying size. A high degree of functionality within the macrocycle is tolerated and the yields for these transformations are typically good to excellent. Since the initial report of a Prins macrocyclization reaction in 1979, examples of this approach did not re-emerge until 2008. However, the use of this method in natural product synthesis has rapidly gained momentum in the synthetic community, with multiple examples of this macrocyclization tactic reported in the recent literature. A "Prins" among reactions: The first report of a Prins macrocyclization appeared in 1979, but only since late 2008 has this strategy gained momentum in natural product synthesis. Convergent, selective, and high yielding, the Prins macrocyclization forms tetrahydropyran-containing macrocycles in a merged C-O and C-C bond-forming event (see scheme).