Inside Cover: A Pyrimidopyrimidine Janus‐AT Nucleoside with Improved Base‐Pairing Properties to both A and T within a DNA Duplex: The Stabilizing Effect of a Second Endocyclic Ring Nitrogen (Chem. Eur. J. 6/2014)

A pyrimidopyrimidine Janus-AT nucleoside NJAT displaying two complementary faces has been rationally designed to simultaneously base pair with A and T bases. NJAT forms stable Watson–Crick base pairs with either T or A, but is significantly destabilizing to duplex-DNA when paired with either a G or C base. In their Communication on page 1495 ff., D. M. Perrin et al. show that this optimized Janus-AT structure allows the selective targeting of AT base pairs and opens exciting prospects for sequence-specific DNA targeting.