Fast and Efficient Postsynthetic DNA Labeling in Cells by Means of Strain-Promoted Sydnone-Alkyne Cycloadditions

Fast and efficient: DNA strands, modified with the novel bioorthogonal reporters sydnones, undergo fast and efficient labeling with cyclooctynes and have the potential to become essential tools for imaging DNA and possibly RNA in cells. Sydnones are highly stable mesoionic 1,3-dipoles that react with cyclooctynes through strain-promoted sydnone-alkyne cycloaddition (SPSAC). Although sydnones have been shown to be valuable bioorthogonal chemical reporters for the labeling of proteins and complex glycans, nucleic acids have not yet been tagged by SPSAC. Evaluation of SPSAC kinetics with model substrates showed fast reactions with cyclooctyne probes (up to k=0.59 M$^{-1}$ s$^{-1}$), and two different sydnones were effectively incorporated into both 2’-deoxyuridines at position 5, and 7-deaza-2’-deoxyadenosines at position 7. These modified nucleosides were synthetically incorporated into single-stranded DNAs, which were successfully postsynthetically labeled with cyclooctyne probes both in vitro and in cells. These results show that sydnones are versatile bioorthogonal tags and have the premise to become essential tools for tracking DNA and potentially RNA in living cells

Enantioselective Baeyer-Villiger oxidation catalyzed by palladium(II) complexes with chiral P,N-ligands

Asymmetric Baeyer-Villiger reaction of symmetrical cyclobutanones 1a-j with urea-hydrogen peroxide (UHP) can be catalyzed by a complex of Pd(II) and the new terpene-derived P,N-ligand 7. The resulting lactones 2a-j were obtained in high yields and with good enantioselectivity (<= 81% ee)

New monoterpene-derived phosphinopyridine ligands and their application in the enantioselective iridium-catalyzed hydrogenation

Pyridine derivatives with a phosphine or phosphinite pendant (1–11) have been synthesized from (+)-α-pinene, (−)-isopinocampheol, and/or (+)-camphor via Kröhnke annulation or another annulation method as the key step for the construction of the pyridine nucleus. The iridium complex of 6 proved to catalyze hydrogenation of the prochiral unfunctionalized alkene 44 with 94% ee, whereas the complex of 2 was most efficient in the hydrogenation of the cinnamyl-type ester 45 (83% ee)

New pyridine N-oxides as chiral organocatalysts in the asymmetric allylation of aromatic aldehydes

Asymmetric allylation of aromatic aldehydes 1 with allyltrichlorosilane (2) can be catalyzed by new terpene-derived bipyridine N,N'-dioxides 12-15 and an axially chiral biisoquinoline dioxide 17b with good enantioselectivities. Dioxides have been found to be more reactive catalysts than their monooxide counterparts. Crown Copyright . All rights reserved

Bioorthogonal labelling of biomolecules: new functional handles and ligation methods

Contains fulltext : 112899.pdf (preprint version ) (Open Access)21 augustus 201