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A Domino Approach to the Enantioselective Total Syntheses of Blennolide C and Gonytolide C
Author(s) -
Tietze Lutz F.,
Jackenkroll Stefan,
Hierold Judith,
Ma Ling,
Waldecker Bernd
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402495
Subject(s) - enantioselective synthesis , domino , dihydroxylation , chemistry , stereochemistry , sharpless asymmetric dihydroxylation , carbonylation , total synthesis , organic chemistry , catalysis , carbon monoxide
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 )‐ i Bu‐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 .