If you had a picture itd be more helpful. Are you asking if you get a chiral product or a racemized product?

The asymmetry in the asymmetric Pictet-Spengler reaction comes either from an existing stereocenter in the precursor or from chiral auxiliaries.

Without these, it depends on the substituents on your substrates and their sterical demand whether the reaction is somewhat stereoselective or fully racemic.

Dear Fleury,

You can see the below paper link for asymmetric Pictet-Spengler reaction of β-phenethylamines:

http://www.arkat-usa.org/get-file/19565/

Thanks for your answers. Here, both reactants (amine and ketone) are achiral and the catalyst is also achiral. The only chiral center is C1 of the THIQ.