title: A domino approach to the enantioselective total syntheses of blennolide C and gonytolide C.
abstract: The first enantioselective total syntheses of the tetrahydroxanthenone (-)-blennolide C (ent-4) and related γ-lactonyl chromanone (-)-gonytolide C (ent-3) are reported. Key to the syntheses is an enantioselective domino-Wacker/carbonylation/methoxylation reaction to set up the stereocentre at C-4a. Various chiral BOXAX ligands were investigated, including novel (S,S)-iBu-BOXAX, and allowed access to chromane 8 in an excellent enantioselectivity of 99 %. The second stereocentre at C-4 was established employing a diastereoselective Sharpless dihydroxylation. An extensive survey of (DHQ)- and (DHQD)-based ligands enabled the preparation of both the anti-isomer 14 a and the syn-isomer 14 b in very good to reasonable selectivities of 13.7:1 and 1:3.7, respectively. While 14 a was further converted to ent-3 and ent-4, 14 b was elaborated to syn-acid 25 and 2'-epi-gonytolide C 28.
authors.affiliation: Institute of Organic and Biomolecular Chemistry, Georg-August-University Göttingen, Tammannstrasse 2, 37077 Göttingen (Germany), Fax: (+49) 551-39-9476. ltietze@gwdg.de.
authors.forename: Lutz F
authors.initials: LF
authors.lastname: Tietze
authors.forename: Stefan
authors.initials: S
authors.lastname: Jackenkroll
authors.forename: Judith
authors.initials: J
authors.lastname: Hierold
authors.forename: Ling
authors.initials: L
authors.lastname: Ma
authors.forename: Bernd
authors.initials: B
authors.lastname: Waldecker
mesh_terms: D001688:Biological Products; D002384:Catalysis; D002867:Chromones / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D044004:Xanthones / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D001688:Biological Products; D002867:Chromones; D044004:Xanthones; C531519:blennolide C
keywords: dihydroxylation; domino reactions; natural products; tetrahydroxanthones; total synthesis