The synthesis of novel aryl spiroketals, which contain a similar substitution
pattern to that present in the antifungal agents the papulacandins, is
described. Thus, spiroketal (7) was obtained from acid-catalysed cyclization
of the keto alcohol (13), and spiroketal (8) was obtained from acid-catalysed
cyclization of keto alcohols (12) and (19). Keto alcohols (12), (13) and (19)
in turn were prepared by ortho-directed lithiation of
amides (10), (11) and oxazoline (17) respectively, followed by reaction with
δ-valerolactone. Substitution of the aromatic ring occurred at the
sterically hindered position ortho to both the methoxy
and ortho-directing metalation group. In an alternative
approach to the synthesis of the desired spiroketals, two
palladium(0)-catalysed coupling strategies were examined. The Stille coupling
between the aryl stannane (24) and iodoglucal (25) resulted in a low yield of
the aryl C-glycoside (21). Likewise, a low yield for the
same coupled product (21) was achieved by a Suzuki coupling between the
arylboronic acid (26) and iodoglucal (25).
新型芳基螺环
酮类化合物的合成与抗真菌剂
木犀草素的取代模式相似。
描述了新型芳基螺环
酮类化合物的合成过程。
描述。因此,通过酸催化环化酮醇 (13) 获得了螺酮醛 (7)。
酸催化环化酮醇 (13) 而得到螺酮醛 (8)。
酮醇 (12) 和 (19) 环化得到螺酮醛 (8)。酮醇 (12)、(13) 和 (19)
又是通过酰胺 (10)、(11)
酰胺(10)、(11)和
噁唑啉(17),然后与
δ-戊内酯反应。芳香环的取代发生在
芳环的取代发生在甲氧基和正交定向
金属化的正交位置上。
和正交定向
金属化基团的正交位置进行。另一种
在合成所需螺
酮类化合物的另一种方法中,两个
钯(0)催化的偶联策略进行了研究。芳基
锡烷
芳基
锡烷 (24) 和
碘代
葡萄糖醛 (25) 之间的 Stille 偶联导致芳基 C-糖苷的低产率。
芳基 C-糖苷(21)的产率较低。同样
同样,通过芳基
硼酸(26)和
碘代
葡萄糖醛(25)之间的铃木偶联,同样的偶联产物(21)的收率也很低。
芳基
硼酸 (26) 和
碘代
葡萄糖醛 (25) 之间的铃木偶联也产生了相同的偶联产物(21)。