title: Absolute structures of some naturally occurring isopropenyldihydrobenzofurans, remirol, remiridiol, angenomalin, and isoangenomalin.
abstract: The absolute structures of some naturally occurring chiral 2-isopropenyl-2,3-dihydrobenzofurans, (+)-remirol (1a), (+)-remiridiol (1b), (+)-angenomalin (2), and (+)-isoangenomalin (3), were studied by respective chiral synthesis. Kinetic resolutions of racemic 2-isopropenyl-2,3-dihydrobenzofurans, 2-isopropenyl-4,6-dimethoxy-2,3-dihydrobenzofuran (4), 4-hydroxy-2-isopropenyl-2,3-dihydrobenzofuran-5-carbaldehyde (8), and 2-isopropenyl-6-(MOM)oxy-2,3-dihydrobenzofuran-5-carbaldehyde (11c), by Sharpless dihydroxylation using (DHQ)(2)AQN or (DHQD)(2)AQN gave the corresponding chiral 2-isopropenyl-2,3-dihydrobenzofurans. Chiral (S)-(+)-4 (99% ee, using (DHQD)(2)AQN) was converted to natural remirol (S)-(+)-1a and then to natural remiridiol (S)-(+)-1b. (S)-(+)-8 (97% ee, using (DHQD)(2)AQN) was converted to natural angenomalin (S)-(+)-2. (R)-(-)-11c (>99% ee, using (DHQ)(2)AQN), was converted to natural isoangenomalin (R)-(+)-3. Thus, the absolute structures of natural remirol (+)-1a and remiridiol (+)-1b and angenomalin (+)-2 were determined to be S, and the structure of natural isoangenomalin (+)-3 was R.
authors.affiliation: Department of Chemistry, Faculty of Science, Toyama University, Gofuku, Toyama 930-8555, Japan. seiji@sci.toyama-u.ac.jp
authors.forename: Seiji
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Shizuko
authors.initials: S
authors.lastname: Muro
authors.forename: Masahide
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Miyazawa
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Hirai
mesh_terms: D019661:Apiaceae / Q000737:chemistry; D001572:Benzofurans / Q000138:chemical synthesis*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003500:Cyclization; D029785:Cyperaceae / Q000737:chemistry; D036602:Eupatorium / Q000737:chemistry; D006900:Hydroxylation; D007202:Indicators and Reagents; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010944:Plants / Q000737:chemistry; D011714:Pyrans; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism
chemical_list: D001572:Benzofurans; D007202:Indicators and Reagents; D008024:Ligands; D011714:Pyrans