Subscribe to RSS
DOI: 10.1055/s-1991-20913
Highly Stereoselective Total Synthesis of the Natural Leukotriene (-)-(5S,6S)-LTA4 Methyl Ester and of Its η-7-10 (Tricarbonyl) Iron Complex
Publication History
Publication Date:
07 March 2002 (online)
The optically active (ee 96 %) leukotriene (5S,6S,7E,9E,11Z, 14Z)-5,6-epoxy-7,9,11,14-icosatetraenoic acid (LTA4) methyl ester (-)-12 and the corresponding η-7-10 (tricarbonyl) iron complex (+)-10 have been synthesized in 12 and 11 steps, respectively and in overall yields of 15 % and 18 % starting from tricarbonyl[methyl (R)-2-5-η-penta-2,4-dienoate]-iron. The key steps involve Friedel-Crafts acylation of the trichloroethyl ester of the starting complex with methyl 5-(chloroformyl)pentanoate, stereoselective transformation into the α-chlorodienone complex (+)-3a, followed by subsequent transformation of the trichloroethyl ester into an aldehyde. Wittig reaction with the known (Z)-(3-nonenylidene)triphenylphosphorane afforded the optically pure (ee 99 %) (tricarbonyl) iron complex (+)-9, possessing the entire functionalized carbon skeleton of the LTA4 methyl ester. This common intermediate was readily converted to the LTA4 methyl ester (-)-12, or its Fe(CO)3 complex (+)-10.