*4.2.1. Determination of ee by derivatization with (R)-menthyl-chloroformate*

This method is based on a quantitative reaction of the product with (*R*)-menthyl-chloroformate. The result of the reaction is a mixture of two diastereomeric carbamates, which can be separated using gas chromatography without the necessity of using any chiral column. This method was successfully validated and nowadays is used for the analysis of many tetrahydroisoquinoline derivatives with a sufficiently low boiling point to GC analysis.

#### *4.2.2. Determination of ee by chiral solvation by Pirkle's alcohol*

Chiral solvation by Pirkle's alcohol ((*R*)-(-)-1-(anthracen-9-yl)-2,2,2-trifluoroethanol) was used to determine *ee* at tetrahydroisoquinoline derivatives with a high boiling point. The method is based on the fact that the products of ATH provide diastereomeric solvates by the reaction with Pirkle's alcohol and each product can be distinguished by NMR analysis.
