Who would have thought before 1986 that an enantiomerically impure catalyst could give a product in an asymmetric synthesis with an enantiomeric excess higher than that of the catalyst? Until then it was assumed that the ee value of the product (ee ) from an asymmetric synthesis was linearly correlated to the ee value of the chiral auxiliary (ee )-in fact a large deviation is possible (see diagram). These nonlinear effects are not only of academic interest since they have a variety of practical uses, which are highlighted in this review.

DL-PDT in comparison with c-PDT was as effective, better tolerated and nearly painless with high patient satisfaction, and may be considered a treatment of choice to meet needs of patients with mild or moderate facial/scalp AKs.

[reaction: see text] A polymer-supported catalyst for Huisgen's [3+2] cycloaddition reaction between azides and alkynes was prepared from copper(I) iodide and Amberlyst A-21. This catalyst was then used in an automated synthesis of 1,4-disubstituted 1,2,3-triazoles giving access to these products in good yields. The catalyst has shown good activity, stability, and recycling capabilities.