Mannuronic acid (5) was transformed into the densely functionalised D,L-dipeptide mimic 1 and subsequently inserted into the cyclic hexapeptide 3. The gulo-configurated seven-membered lactam 1 exhibits an inverted ring conformation compared to the previously described L,L-dipeptide mimic 2. In spite of this considerable difference, both prefer the same i to i + 1 positions of a β-turn within a cyclic hexapeptide.
曼
脲酸(5)被转化成了功能密集的 D,L-二
肽模拟物 1,随后被插入到环状六肽 3 中。与之前描述的 L,L-二肽拟态物 2 相比,古洛构型的七元内酰胺 1 呈倒环构象。