Open-chain acetonides of D-galactono-1,4-lactone as starting materials for pyrrolidines, azepanes and 5-azidomethyltetrahydrofuran-2-carboxylates: monomers for polyhydroxylated nylon and for tetrahydrofuran carbopeptoids
作者:Daniel D. Long、Rebecca J. E. Stetz、Robert J. Nash、Daniel G. Marquess、Janet D. Lloyd、Ana L. Winters、Naoki Asano、George W. J. Fleet
DOI:10.1039/a809807g
日期:——
Treatment of D-galactono-1,4-lactone with dimethoxypropane in acetone in the presence of tosic acid forms methyl 2,3:5,6-di-O-isopropylidene-D-galactonate 6 (with only the secondary hydroxy group at C-4 unprotected) and methyl 2,3:4,5-di-O-isopropylidene-D-galactonate 5 (with only the primary hydroxy group at C-6 unprotected) in yields of 20% and 78%, respectively. The value of such easily accessible intermediates is illustrated by the synthesis of 1,4-dideoxy-1,4-imino-D-glucitol 16 (a pyrrolidine), and for the efficient preparation of 6-azido-6-deoxy-D-galactono-1,4-lactone 22. The conversion of 22 to a seven-membered galactonolactam 21 (a tetrahydroxycaprolactam) may provide access to hydroxylated nylon polymers. The galactonolactam 21 has no significant inhibitory effect on a number of glycosidases. Reaction of 22 with triflic anhydride gives two epimeric 5-(azidomethyl)tetrahydrofuran-2-carboxylates which provide starting materials for two series of carbopeptoids, one of which probably has a helical structure and the other a structure reminiscent of a β-turn.
在丙酮中,在二甲氧基丙烷和托西酸的作用下,D-半乳糖酸-1,4-内酯可分别生成20%和78%的甲基2,3:5,6-二-O-异亚丙基-D-半乳糖酸酯6(仅C-4上的次羟基未受保护)和甲基2,3:4,5-二-O-异亚丙基-D-半乳糖酸酯5(仅C-6上的主羟基未受保护)。1,4-二脱氧-1,4-亚氨基-D-葡萄糖醇16(一种吡咯烷)的合成以及6-叠氮-6-脱氧-D-半乳糖酸-1,4-内酯22的高效制备都说明了这种易得中间体的价值。将22转化为七元半乳糖内酰胺21(一种四羟基己内酰胺)可得到羟基化尼龙聚合物。半乳糖内酰胺21对多种糖苷酶没有明显的抑制作用。22与三氟甲磺酸酐反应可生成两种外消旋5-(叠氮甲基)四氢呋喃-2-羧酸酯,它们可作为两种系列碳青霉烯类药物的起始原料