A convergent total synthesis of lamellarins S and Z is described. The synthesis features a halogen dance of an easily accessible α,β-dibromopyrrole promoted by an ester moiety. The resultant β,β'-dibromopyrrole undergoes a ligandcontrolled Suzuki-Miyaura coupling to provide a range of diarylated pyrrole derivatives. The established synthetic method was also applicable to the synthesis of ningalin B, and lukianols A and B.
A bottom-up
synthesis of lamellarins G, J, L, and Z was achieved
via one-pot halogen dance/Negishi coupling of a lithiated dibromopyrrole
derivative. The easily accessible dibromopyrrole bearing an ester
moiety underwent halogen dance smoothly at −78 °C within
10 min. The resultant α-pyrrolyllithium was transmetalated to
the corresponding organozinc species, which was then coupled with
an aryl iodide in the presence of catalytic palladium to provide the
fully substituted pyrrole. Subsequent halogen–lithium exchange
was performed to incorporate a boronate group exclusively at the β
position proximal to the ester moiety. This synthetic intermediate
allowed stepwise diarylation for the total synthesis of lamellarins
G, J, L, and Z.
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