A new method has been established for the preparation of C 2-oxidized
5,5-spiroacetals, which are key intermediates for the synthesis of the
bis-spiroacetal moiety of the spirolides. A bridged
orthoester was used as a masked carboxylic acid in the preparation of these
bicyclic oxaspirolactones. The synthesis of chiral lactone (12), a building
block for the synthesis of the spirolides, is also reported. The two chiral
centres in lactone (12) were assembled by addition of a chiral crotyl borane
to an aldehyde. The structure of lactone (12) was determined by single-crystal
X-ray diffraction; orthorhombic space group
P212121
(No. 19), a 12.437(2), b
23.881(4), c 7.545(1) Å, V
2240.9(5) Å3, R(F) 0.0460,
and Rw(F)
0.0458.
建立了一种新方法来制备 C 2-氧化的
5,5-螺乙醛的新方法。
双螺乙醛分子的关键中间体。桥接的
在制备这些双环氧杂螺内酯的过程中,使用了桥接的原酯作为掩蔽羧酸。
双环氧杂螺内酯。合成手性内酯 (12)
手性内酯 (12) 的合成也有报道。内酯 (12) 中的两个手性
内酯 (12) 中的两个手性中心是通过将手性巴豆硼烷加到醛中而形成的。
加到一个醛中。内酯 (12) 的结构是通过单晶
X 射线衍射;正交空间群
P212121
(第 19 号),a 12.437(2),b
23.881(4), c 7.545(1) Å, V
2240.9(5) Ω3,r(F) 0.0460、
和 Rw(F)
0.0458.