title: Total synthesis of the potent anticancer Aglaia metabolites (-)-silvestrol and (-)-episilvestrol and the active analogue (-)-4'-desmethoxyepisilvestrol.
abstract: Total synthesis of the anticancer 1,4-dioxane containing natural products silvestrol (1) and episilvestrol (2) is described by an approach based on the proposed biosynthesis of these novel compounds. The key steps included an oxidative rearrangement of the protected d-glucose derivative 11 to afford the 1,4-dioxane 12, which could be elaborated to the coupling partner 5 and a photochemical [3 + 2]-cycloadditon between the 3-hydroxyflavone 27 and methyl cinnamate followed by base-induced alpha-ketol rearrangement and reduction to give the cyclopentabenzofuran core 33. The core (-)-6 and 1,4-dioxane fragment 5 were united by a highly stereoselective Mitsunobu coupling with the modified azodicarboxylate DMEAD to afford the axial coupled product 36. Deprotection then gave episilvestrol (2). Silvestrol (1) was synthesized by a coupling between core (-)-6 and the dioxane 44 followed by deprotection. Compound 1 was also synthesized from episilvestrol (2) by a Mitsunobu inversion. In addition, the analogue 4'-desmethoxyepisilvestrol (46) was synthesized via the same route. It was found that 46 and episilvestrol 2 displayed an unexpected concentration-dependent chemical shift variation for the nonexchangeable dioxane protons. Synthetic compounds 1, 2, 38, 46, and 54 were tested against cancer cells lines, and it was found that the stereochemistry of the core was critical for activity. Synthetic analogue 4'-desmethoxyepisilvestrol (46) was also active against lung and colon cancer cell lines.
authors.affiliation: CSIRO Molecular and Health Technologies, Bayview Avenue, Victoria 3168, Australia.
authors.forename: Tim E
authors.initials: TE
authors.lastname: Adams
authors.forename: Mariana
authors.initials: M
authors.lastname: El Sous
authors.forename: Bill C
authors.initials: BC
authors.lastname: Hawkins
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hirner
authors.forename: Georgina
authors.initials: G
authors.lastname: Holloway
authors.forename: Mui Ling
authors.initials: ML
authors.lastname: Khoo
authors.forename: David J
authors.initials: DJ
authors.lastname: Owen
authors.forename: G Paul
authors.initials: GP
authors.lastname: Savage
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Scammells
authors.forename: Mark A
authors.initials: MA
authors.lastname: Rizzacasa
mesh_terms: D031602:Aglaia / Q000737:chemistry* / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001572:Benzofurans / Q000737:chemistry / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D014315:Triterpenes / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
chemical_list: C539407:4'-desmethoxyepisilvestrol; D000972:Antineoplastic Agents, Phytogenic; D001572:Benzofurans; D014315:Triterpenes; C489893:episilvestrol; C489897:silvestrol; C105430:benzofuran