Synthesis and Absolute Configuration of (S)-(−)- and (R)-(+)-2,3-Dihydro-2-(1-methylethenyl)-6-methoxybenzofuran

Abstract

Resolution of racemic 2,3-dihydro-2-carboxy-6-methoxybenzofuran (2) by recrystallizations of diastereomeric salts prepared with (S)-(-)-alpha-methylbenzylamine and (R)-(+)-alpha-methylbenzylamine gave the starting materials for the four-step total syntheses of (S)-(-)-2,3-dihydro-2-(1-methylethenyl)-6-methoxybenzofuran (1a) and (R)-(+)-2,3-dihydro-2-(1-methylethenyl)-6-methoxybenzofuran (1b). Their absolute configuration was established by chemical correlation.

Enzymatic hydrolysis of esters from 2-carboxy-6-methoxy-2,3-dihydrobenzofuran acid

“…Based on these results, it was possible to establish that the mixture of dioxane-ter-butanol 9:1 (D-tB 9:1) was the most adequate for evaluating the behavior of the other esters during the enzymatic reaction, in order to determine the effect of the chain length on the resolution process. The absolute configuration of the obtained acid was determined by the comparison of the optical rotation of the methyl esters with reported data (Tovar-Miranda et al, 1999).…”

“…The reaction products were identified by Nuclear Magnetic Resonance, 1 H and 13 C NMR measurements were performed on a Varian Mercury Plus 300BB using deuterated chloroform (CDCl3) solutions containing TMS as internal standard and compared with literature reports (Tovar-Miranda et al, 1999). Enantiomeric excesses were determined as the corresponding methyl esters by High Performance Liquid Chromatography (HPLC) using a Chiracel-OD column (250 mm length x 4.6 mm i.d.)…”

“…The optical rotation was determined in a Perkin-Elmer polarimeter, Mod. 341 and compared with those previously descrybed (Tovar-Miranda et al, 1999). TLC were performed on aluminium sheets (5 × 5 cm) silica gel 60 F254 from Merck, eluted with hexane-ethyl acetate (80:20) and detected with UV-lamp at 254 nm.…”

“…13168. Fax: +1 228 841-89-32. phenylethylamine and amphetamines (Harada et al, 1968;Tovar-Miranda et al, 1999). This last procedure is very tedious because the methodology requires firstly the salt to be a solid; then this salt must be recrystallized several times to reach a constant optical rotation.…”

Synthesis and anti-obesity effects in vivo of Crotadihydrofuran C as a novel PPARγ antagonist from Crotalaria albida

“…The white precipitate formed was filtered and washed with Me 2 CO to give the homogeneous salt ( S )-(-)- 9a (4.9 g, 98% yield); white solid; mp 155–160 °C; [R] D 20 −4.83° ( c 0.1, MeOH)38 (S35 Fig). …”