Synthesis of 4-[(E)-1-Alkenyl]-2-hydroxybutanolides and (Z)-4-Alkylidene-2-butenolides through Cycloadditions Using a Phosphorus-Functionalized Nitrile Oxide
Horner–Emmons Olefination of 4-Hydroxy-2-oxoalkylphosphonates and Related Compounds: Applications to the Syntheses of (±)-Gingerol, (±)-Yashabushiketol, and (±)-Dihydroyashabushiketol
作者:Otohiko Tsuge、Shuji Kanemasa、Norihiko Nakagawa、Hiroyuki Suga
DOI:10.1246/bcsj.60.4091
日期:1987.11
Horner–Emmons olefination of 4-hydroxy-2-oxoalkylphosphonates, readily available by hydrogenation of 5-substituted 3-phosphinylmethyl-2-isoxazolines, gives mainly E-isomers of 1-hydroxy-4-alken-3-ones bearing a variety of substituents at the 1-position. Use of the combination of triethylamine (or DBU)+lithium bromide as a weak base on the O-unprotected phosphonates is favored. Similar olefinations on the isoxazolines, 2-oxo-3-alkenylphosphonates, and 4-alkoxy-2-oxoalkylphosphonates have been also examined. Their synthetic applications to (±)-Gingerol, (±)-Yashabushiketol, and (±)-Dihydroyashabushiketol are described.