Two isomeric dialkynylpyrene phosphoramidites and their incorporation into oligonucleotides are described. The pyrene units closely resemble the well-known perylene bisimide dye PDI with regard to the ability to self-organize within a DNA duplex. In addition, dialkynylpyrenes exhibit significant monomer and remarkably strong excimer fluorescence. The dialkynylpyrene building blocks are promising candidates for applications in diagnostic tools, such as excimer-based molecular beacons, as well as for novel DNA-based materials with special optical properties.

[reaction: see text] Starting from natural proline, a practical chirospecific synthesis of spirocyclic beta-lactams of type 2 is described when a methylene moiety showing minimal steric demand is employed as a constraint element for adjusting the dihedral angle psi(i + 1). Employing the concept of self-reproduction of chirality, C-formylation of the oxazolidinone 5 afforded the key intermediate 7 taking advantage of an intermediate protection of the bridging element as a vinyl moiety. NMR- and IR-based conformational studies clearly indicated that spiro-beta-lactams of type 2 can serve as efficient beta-turn nucleators.

Switched on: The fluorescence emission of a DNA‐based optical switch can be reversibly switched from blue to green using modulating light of different wavelengths (see picture). The device is based on the hybridization of two pyrene‐functionalized DNA strands in the presence of a photochromic azobenzene‐containing effector ligand. Hybridization occurs only with the cis‐configured ligand, and results in pyrene excimer fluorescence.

The neurotensin C-terminal hexapeptide, NT(8-13), which has been found to adopt a beta-strand-like conformation while bound to the NT1 receptor, was modified by the introduction of conformational constraints. Synthesis of the four stereoisomeric 4.4-spirolactams 1-4 and subsequent NT1 receptor binding studies showed that the restriction of psi(Pro10) to approximately 130 degrees leads to a more than 1000-fold increase of binding affinity for 1 (Ki = 12 nM) when compared to the more flexible analogue [NMeTyr11]NT(8-13).