NaHMDS/B(C6F5)3-promoted diastereoselective Friedel-Crafts alkylation of indoles/pyrroles with N-tert-butanesulfinylimines: towards the asymmetric synthesis of bisindole alkaloid Calcicamide B.

This study proposed an innovative and pragmatic approach to the asymmetric Friedel-Crafts reaction by employing indoles/pyrroles and chiral N-tert-butanesulfinylimines promoted by NaHMDS/B(C6F5)3. This method effectively produces enantioenriched α-(3-indolyl)glycine and α-(2-pyrrolyl)glycine derivatives, which can be readily transformed into the crucial chiral diamine skeletons. The first successful asymmetric total synthesis of marine-derived anti-tumor bisindole alkaloid Calcicamide B was achieved by employing this reaction as a crucial chiral control step.