Synthetic studies on spiroketal natural products. III. Enantioselective synthesis of 1,6-dioxaspiro(4.5)decane compounds.
作者:CHUZO IWATA、YASUNORI MORITANI、KENJI SUGIYAMA、HITOSHI IZAKI、TOSHIO KUROKI、TAKESHI IMANISHI
DOI:10.1248/cpb.36.4785
日期:——
Two enantiomers of 1, 6-dioxaspiro [4.5] decane (1) and all four stereoisomers of 2-methyl-1, 6-dioxaspiro [4.5] decane (an insect pheromone)(9) were successfully synthesized via a crucial step, an asymmetric five-membered ring cyclization induced by a sulfinyl chirality. The alcohol (6), prepared from the optically active sulfoxide (2), was treated with potassium hydride to give the spiroketal (7), which was transformed into the isomer (8) by acid. Reductive desulfurization of these products furnished R-1 and S-1, respectively. The ketone (10), also prepared from 2, was reduced with diisobutylaluminum hydride (DIBAL) or DIBAL-ZnCl2 to afford selectively 15a or 15b, respectively. Base-catalyzedicyclization gave 21a and 21b, which were convertible to 22a and 22b under acidic conditions. The four isomers (21a, 21b, 22a, and 22b) were efficiently transformed into 9a, 9b, 9c, and 9d by removal of the chiral auxiliary.
成功合成了1, 6-二氧杂螺[4.5]十烷(1)的两个对映体以及2-甲基-1, 6-二氧杂螺[4.5]十烷(昆虫信息素)(9)的所有四个立体异构体,关键步骤是一种由硫酰手性诱导的不对称五元环环化反应。由光学活性的硫氧化物(2)制备的醇(6),与氢化钾反应生成螺酮(7),该物质在酸的作用下转化为异构体(8)。这些化合物的还原脱硫反应分别生成R-1和S-1。酮(10),同样由2制备,经过二异丁基铝氢化物(DIBAL)或DIBAL-ZnCl2还原,分别选择性地得到15a或15b。碱催化的环化反应生成21a和21b,在酸性条件下可以转化为22a和22b。通过去除手性辅佐基,这四个异构体(21a、21b、22a和22b)有效地转化为9a、9b、9c和9d。