Silver‐Mediated Homochiral and Heterochiral α‐dC/β‐dC Base Pairs: Synthesis of α‐dC through Glycosylation and Impact of Consecutive, Isolated, and Multiple Metal Ion Pairs on DNA Stability

Isolated and consecutive heterochiral α‐dC– base pairs have been incorporated into 12‐mer oligonucleotide duplexes at various positions, thereby replacing Watson–Crick pairs. To this end, a new synthesis of the α‐d anomer of dC has been developed, and oligonucleotides containing α‐dC residues have been synthesized. Silver‐mediated base pairs were formed upon the addition of silver ions. Furthermore, we have established that heterochiral α‐dC–dC base pairs can approach the stability of a Watson–Crick pair, whereas homochiral dC–dC pairs are significantly less stable. A positional change of the silver‐mediated base pairs affects the duplex stability and reveals the nearest‐neighbor influence. When the number of silver ions was equivalent to the number of duplex base pairs (12), non‐melting silver‐rich complexes were formed. Structural changes have been supported by circular dichroism (CD) spectra, which showed that the B‐DNA structure was maintained whilst the silver ion concentration was low. At high silver ion concentration, silver‐rich complexes displaying different CD spectra were formed.