Enantioselective synthesis of a trans-7,8-dimethoxycalamenene.
trans-7,8-dimethoxy-11,12-dehydrocalamenene, a projected intermediate for the total synthesis of marine serrulatane and amphilectane diterpenes, was efficiently synthesized. Starting from a styrene, asymmetric Rh-catalyzed hydroboration using a novel chiral P,P-bidentate ligand afforded an organoboron intermediate (93% ee) which was directly used for C-C bond formation (double homologation, Suzuki coupling). The 1,4-trans-disubstituted tetralin skeleton was selectively formed by a Friedel-Crafts-type cationic cyclization under strictly aprotic conditions (Me2AlCl) to suppress a remarkable proton-catalyzed disproportionation via diastereoselective hydride transfer.
Institute of Organic Chemistry, University of Cologne, Greinstr. 4, 50939 Köln, Germany.
Susen
S
Werle
Thorsten
T
Fey
Jörg M
JM
Neudörfl
Hans-Günther
HG
Schmalz
D003500:Cyclization; D015394:Molecular Structure; D013237:Stereoisomerism; D020058:Styrene / Q000737:chemistry; D013729:Terpenes / Q000138:chemical synthesis / Q000737:chemistry*
D013729:Terpenes; C524013:trans-7,8-dimethoxycalamenene; D020058:Styrene