Cover Picture

The cover picture shows the catalysis of a Diels-Alder reaction by an artificial ribozyme. A series of anthracene and maleimide derivatives are converted with high efficiency, and with suitable substituents enantioselectivites greater than 95 % ee can be achieved. Shown in the mirror is a picture of a synthetic ribozyme built from unnatural L-ribonucleotides, which, as expected, catalyzes the formation of the other enantiomer of the product. The threadlike molecules in the background symbolize the combinatorial RNA pool from which the ribozymes were originally isolated. More about the fascinating properties of these ribozymes is reported by J?schke and co-workers on page 4576 ff. (The 3D model of a folded RNA molecule was generated with the program MOLMOL from the data set 1EHT.pdb.)