MilliporeSigma has begun distributing the PPA and PAQ directing groups, which the Engle lab first described at the end of 2017. Thanks to MilliporeSigma for helping to make these useful auxiliaries more readily available to end-users across the world.
PPA directing group for amine substrates:
https://www.sigmaaldrich.com/catalog/product/aldrich/901251?lang=en®ion=US
PAQ directing group for carboxylic acid substrates:
https://www.sigmaaldrich.com/catalog/product/aldrich/901250?lang=en®ion=US
Molecular Complexity through Catalysis 