Post-synthetic transamination at position N4 of cytosine in oligonucleotides assembled with routinely used phosphoramidites.

The commercially available and cheap nucleotide phosphoramidites are routinely used for the oligonucleotide (ODN) assembly. T, isobutyryl-dG (iBudG), benzoyl-dA (BzdA), acetyl-dC (AcdC) and benzoyl-dC (BzdC) derivatives are sufficient to produce orthogonally protected ODNs. Clean and efficient (ca. 30%-70% yield) post-synthetic amination of an ODN assembled with such phosphoramidites was selectively achieved at the N4 position of a singly introduced BzdC. Such a method represents a novel and cheap strategy for the user-friendly post-modification of oligonucleotides at the internal position.

Alkali-Glass Behavior in Honeycomb-Type Layered Li3-xNaxNi2SbO6 Solid Solution.

Layered oxide compositions Li3-xNaxNi2SbO6 have been prepared by solid-state synthesis. A complete solid solution is evidenced and characterized by X-ray and neutron diffraction as well as 7Li and 23Na solid-state nuclear magnetic resonance spectroscopy. The transition-metal layer is characterized by the classic honeycomb Ni2+/Sb5+ ordering, whereas a more uncommon randomly mixed occupancy of lithium and sodium is evidenced within the alkali interslab space. In situ X-ray diffraction and density functional theory calculations show that this alkali disordered feature is entropically driven. Fast cooling then appears as a synthesis root to confine bidimensional alkali glass within crystalline layered oxides.