摘要:
A practical synthesis of a highly enantioselective, C3-symmetric host molecule (2) has been developed. The basic strategy is a significant improvement over the relatively lengthy previous synthesis and involves direct addition of a Boc-tyrosine amide anion derivative 4 to methyl 3,5-bis(bromomethyl)-benzoate to give an advanced intermediate (5). The final step, a triple macrolactamization, closes three 19-membered rings simultaneously to produce the bridged macrotricyclic receptor in 70-80% yield.