Synthesis and Elimination Reaction of <i>O</i>-Methyl Derivatives of Methyl (Methyl α-<scp>d</scp>-Glucopyranosido)uronate

Abstract

Abstract Several methyl ethers [2,3,4-tri-O-methyl- (1), 4-O-methyl- (2), 3-O-methyl- (3), and 2-O-methyl- (4)] of methyl (methyl α-d-glucopyranosido)uronate were used as model compounds for the examination of β-elimination reaction. 1 was purely synthesized from methyl α-d-glucopyranoside and both 3 and 4 were newly synthesized via the corresponding methyl ethers of methyl α-d-glucopyranoside. The condition of β-elimination reaction was examined using 1 as a model compound. It was shown that β-elimination reaction occurred only when an alkoxide was used as a base. The yield of the unsaturated product, i. e., methyl (methyl 4-deoxy-2,3-di-O-methyl-β-l-threo-hex-4-enopyranosido)uronate (13) was about 40–50% by sodium methoxide in methanol at 60–70°C, and 70–80% by potassium t-butoxide in t-butyl alcohol even at room temperature. In both cases the reaction was completed within several minutes. The β-elimination reaction was followed by UV spectra using the molecular extinction coefficient of purely isolated 13, and the reaction products were examined by gas-liquid chromatography. The β-elimination product of 2 was also obtained in good yield, but that of 3 in very poor yield.