作者:Wolf Matthias Pankau、Wolfgang Kreiser
DOI:10.1002/(sici)1522-2675(19981111)81:11<1997::aid-hlca1997>3.0.co;2-v
日期:1998.11.11
(-)-D-Noviose ((-)-22), a rare sugar, was synthesized starting from the optically active building block (-)1 in seven steps. The first step of this route, the introduction of a methyl-ether group under Lewis-acidic conditions, left the acetoxy group untouched and thereby preserved the absolute configuration in the product 2 (Scheme 2). Next, the double bond of methyl ether 2 was cis-dihydroxylated leading selectively to 3. After saponification of the acetoxy group of 3 the two vicinal cis OH groups of 17 were selectively protected as the cyclic carbonate 18 (Scheme 4). This kind of protection was essential to achieve the proper regioselectivity in the Baeyer-Villiger rearrangement of the cyclopentanone derivative 19 that was obtained after oxidation of the remaining OH group of 18. Lactone 20 was the major product of this rearrangement. Final reduction to the corresponding lactol (cyclic hemiacetal) with diisobutylaluminium hydride (DIBAH) at low temperature was accompanied by reductive cleavage of the protecting cyclic carbonate moiety thereby leading directly to (-)-D-noviose ((-)-22).
(-)-D-向日葵糖((-)-22)是一种稀有糖,从光学活性结构单元(-)1出发,经七步合成。该路线的第一步是在路易斯酸条件下引入甲基醚基团,该步骤未触碰乙酰氧基,从而保留了产物2中的绝对构型(方案2)。接下来,甲基醚2的双键进行顺式二羟化,选择性地得到3。在对3的乙酰氧基进行皂化后,3中邻近的两个顺式OH基团被选择性地保护为环状碳酸酯18(方案4)。这种保护方式对于后续环戊酮衍生物19的贝叶斯-维尔格重排反应中获得合适的区域选择性至关重要,而19是由18剩余的OH基团氧化得到的。贝叶斯-维尔格重排的主要产物是环状酯20。最后,使用二异丁基铝氢化物(DIBAH)在低温下将环状酯20还原为相应的环状半缩醛(乳糖醇),同时伴随环状碳酸酯保护基团的还原裂解,从而直接得到(-)-D-向日葵糖((-)-22)。