Ring-closing alkyne metathesis. Application to the total synthesis of sophorolipid lactone.
The first total synthesis of a major component of the microbial biosurfactant sophorolipid has been achieved. This approach to the 26-membered macrolide 1 containing a Z-configured alkene group in its lipidic tether spanning the sophorose backbone is based on a ring-closing metathesis reaction of diyne 21 catalyzed by Mo[N(t-Bu)(Ar)](3) (5; Ar = 3,5-dimethylphenyl) activated in situ by CH(2)Cl(2), followed by Lindlar reduction of the resulting cycloalkyne 22. The two beta-glycosidic linkages of compound 21 were installed by means of the glucal epoxide method and a modified Koenigs-Knorr reaction promoted by AgOTf/lutidine, respectively.
Fürstner
A
A
Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim/Ruhr, Germany. fuerstner@mpi-muelheim.mpg.de
Radkowski
K
K
Grabowski
J
J
Wirtz
C
C
Mynott
R
R