Unexpected endo selectivity of conjugate nucleophilic addition to an arene-Cr(CO)3 complex: enantioselective synthesis of the diterpene 11-epi-helioporin B.
[reaction: see text]. Starting from a nonracemic planar-chiral arene tricarbonyl chromium complex, an epimer of the bioactive marine diterpene helioporin B was synthesized in a highly stereoselective fashion. The stereostructure of the product (11-epi-helioporin B) corresponds to that of other serrulatane-type natural products. In a key step of the synthesis, 2-lithioacetonitrile undergoes conjugate nucleophilic addition to an unsaturated complex. Remarkably, this addition occurs in an endo mode, i.e., from the complexed face of the pi-ligand.
Dehmel
F
F
Institut für Organische Chemie, Universität zu Köln, Greinstrasse 4, D-50939 Köln, Germany.
Schmalz
H G
HG
D001549:Benzamides / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004224:Diterpenes / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D011743:Pyrimidines / Q000737:chemistry*; D013237:Stereoisomerism; D005466:Fluorocarbons
D001549:Benzamides; D002857:Chromium; D004224:Diterpenes; D007202:Indicators and Reagents; D009942:Organometallic Compounds; D011743:Pyrimidines; C442273:N-(pyrimidin-2-yl)pentafluorobenzamide; D005466:Fluorocarbons