Purine–Purine Base Pairs in Parallel DNA: β-D Anomeric 8-Aza-7-deazaisoguanine and 7-Functionalized Conjugates Form Stable Base Pairs with α-D 5-Aza-7-deaza-2′-deoxyguanosine

Anomeric purine-purine DNA represents a new recognition system with strands in parallel orientation. This work investigates the new heterochiral system and the positional impact of nucleobase functionalization. Tracts of anomeric isoguanine/8-aza-7-deazaisoguanine base pairs with 5-aza-7-deazaguanine were embedded in anomeric Watson-Crick DNA. It was discovered that stable purine-purine base pairs are formed in anomeric DNA. Nucleobase functionalization of the novel base pair system with short ethynyl and bulky octadiynyl chains showed that the position of functionalization is critical. From