Iterative, one-directional, boron-mediated aldol chain extensions, using the dipropionyl reagent (R)-1-(benzyloxy)-2-methylpentan-3-one 7, have enabled the highly diastereoselective assembly of the stereoregular heptapropionates 5 and 6. The synthetic sequence developed permits structural diversity through variation in the stereochemical nature of the aldolisation and reduction steps, together with the choice of the chiral ketone employed at each iteration. The heptapropionate 5 has been shown to represent an example of a fully flexible molecule, whose backbone nevertheless adopts a single preferred conformation. It forms part of a family of conformationally controlled polyols, exploiting the avoidance of syn-pentane interactions and the preference for preorganisation through intramolecular hydrogen bonding.
利用二
丙酸试剂 (R)-1-(benzyloxy)-2-methylpentan-3-one 7,通过迭代、单向、
硼介导的醛醇链延伸,实现了立体对映的庚
丙酸酯 5 和 6 的高非对映选择性组装。通过改变醛化和还原步骤的立体
化学性质,以及选择每次迭代所使用的手性酮,所开发的合成序列允许结构的多样性。研究表明,庚
丙酸酯 5 是完全柔性分子的一个例子,但其骨架采用了单一的优选构象。它构成了构象控制多元醇家族的一部分,利用了避免同
戊烷相互作用和通过分子内氢键预组织的偏好。