Pyrroloindole-Based Dynamic Combinatorial Chemistry

We report a new class of building blocks for Dynamic Combinatorial Chemistry (DCC) based on the pyrroloindole scaffold. The attachment of L-cysteine on the oc, a' positions of the core makes the molecule suitable for disulfide exchange in aqueous dynamic combinatorial libraries (DCLs). The synthesis or the core follows a modified version of the Knoevenagel-Hemetsberger approach. The new building block (l-PI) is fluorescent (Φ = 48%) and relatively stable towards thermal and photodegradation. The chirality of the cysteine is transferred to the electron-rich pyrroloindole core. Homo-and heterochiral DCLs of l-PI with electron-deficient l-and d-naphthalenediimide (NDI) lead to similar library distributions regardless of the enantiomer used. When no salt is present, the major component is a dimer, while dimers and tetramers are obtained at increased ionic strength.