Fig. 4: Mechanistic considerations and stereo-divergent synthesis.

A Cyclization of enantioenriched 4b with (R)-CPA-7; B cyclization of enantioenriched 4b with (S)-CPA-7; C cyclization of enantioenriched 4b with racemic CPA-7; D Cyclization of racemic 4b with (R)-CPA-7; E stereo-divergent synthesis; F proposed reaction pathway and transition states.