The reaction of the lactols 1a-1d, with malonic acid in hot dimethyl sulfoxide, in the presence of piperidinium acetate as catalyst, gives the corresponding (tetrahydrofuran-2-yl)acetic acids 2a,c and (tetrahydropyran-2-yl)acetic acids 2b,d in high yield (65-75%). While the synthesis of the (6-methyltetrahydropyran-2-yl)acetic acid (2d) is highly stereoselective (cis/trans ratio 20:1), no stereoselection was observed with the (5-methyltetrahydrofuran-2-yl)acetic acid (2c) (cis/trans ratio 1:1). This reaction was applied for the synthesis of natural (+)-(S,S)-(cis-6-methyltetrahydropyran-2-yl)acetic acid (7), minor constituent of the glandular secretion of the civet cat.
内酯 1a-1d 在热
二甲亚砜中与
丙二酸反应,在
乙酸哌啶盐作为催化剂的存在下,可以得到相应的(
四氢呋喃-2-基)
乙酸 2a,c 和(
四氢吡喃-2-基)
乙酸 2b,d,产率高(65-75%)。(6-甲基
四氢吡喃-2-基)
乙酸(2d)的合成具有高度的立体选择性(顺式/反式比为 20:1),而(5-甲基
四氢呋喃-2-基)
乙酸(2c)则没有立体选择性(顺式/反式比为 1:1)。该反应被用于合成天然的(+)-(S,S)-(顺式-6-甲基
四氢吡喃-2-基)
乙酸(7),这是狸猫腺体分泌物的次要成分。