Synthetic Studies on Pyridomycin. III. Chiral Synthesis of (2<i>R</i>,2<i>S</i>)-(−)-2,3-Dihydroxy-3-methylpentanoic Acid from Sugar Derivative
作者:Mitsuhiro Kinoshita、Hiroshi Hamazaki、Masaki Awamura
DOI:10.1246/bcsj.51.3595
日期:1978.12
successive 3,4-O-isopropylidenation, debenzoylation, hydrogenolysis, and two-stage oxidation with periodate-hypoiodite afforded (4R,5S)-(+)-5-ethyl-2,2,5-trimethyl-1,3-dioxolane-4-carboxylic acid (15) in 24.6% overall yield from 5. Hydrolysis of 15 gave (2R,3S)-(−)-2,3-dihydroxy-3-methylpentanoic acid. The acetonide 15 is usefull as a synthon for pyridomycin synthesis.
3-O-benzyl-6-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranos-5-ulose (5) 与乙基溴化镁的格氏反应生成 3-O-benzyl-6-deoxy- 5-C-乙基-1,2-O-异亚丙基-α-D-呋喃葡萄糖 (6) 作为主要产物,立体选择性为 91%。6 的水解,然后是连续的高碘酸盐氧化和氢化铝锂还原,得到 2-O-benzyl-5-deoxy-4-C-ethyl-D-arabinitol。9 的选择性苯甲酰化,然后依次进行 3,4-O-异亚丙基化、脱苯甲酰化、氢解和高碘酸盐-次碘酸盐的两阶段氧化,得到 (4R,5S)-(+)-5-乙基-2,2,5-三甲基-1,3-二氧戊环-4-羧酸(15),来自5的总产率为24.6%。15的水解得到(2R,3S)-(-)-2,3-二羟基-3-甲基戊酸。丙酮化物 15 可用作吡啶霉素合成的合成子。