title: Synthesis of γ- and δ-lactone natural products by employing a trans-cis isomerization/lactonization strategy.
abstract: Alkaline hydrolysis of 4-hydroxy- or/and 5-hydroxy-(2E)-alkenoate followed by acid treatment gave the corresponding (2E)-alkenoic acids which were subjected to lactone formation reaction without further purification. The crude acids were treated with 2,4,6-trichlorobenzoyl chloride in pyridine to afford γ-lactone or δ-lactone, respectively, accompanied by trans-cis isomerization. By this procedure, (±)-(4,5)-trans-5-benzyloxy-2-hexen-4-olide (90% overall yield), (S)-5-hydroxy-2-penten-4-olide (86% overall yield), (4S,5R)-5-hydroxy-2-hexen-4-olide (86% overall yield), (4R,5S)-5-hydroxy-2-hexen-4-olide (82% overall yield), (S)-parasorbic acid (58% overall yield) and natural product, (5R,7S)-7-hydroxy-2-octen-5-olide (euscapholide: 20% overall yield) were synthesized.
authors.affiliation: School of Pharmaceutical Sciences, International University of Health and Welfare, 2600–1 Kitakanemaru, Ohtawara, Tochigi, Japan.
authors.forename: Machiko
authors.initials: M
authors.lastname: Ono
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kato
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Akita
mesh_terms: D001688:Biological Products / Q000138:chemical synthesis* / Q000737:chemistry; D006868:Hydrolysis; D007783:Lactones / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001688:Biological Products; D007783:Lactones; C005408:parasorbic acid