Assembly of Bleomycin Saccharide-Decorated Spherical Nucleic Acids.

Glyco-decorated spherical nucleic acids (SNAs) may be attractive delivery vehicles, emphasizing the sugar-specific effect on the outer sphere of the construct and at the same time hiding unfavorable distribution properties of the loaded oligonucleotides. As examples of such nanoparticles, tripodal sugar constituents of bleomycin were synthesized and conjugated with a fluorescence-labeled antisense oligonucleotide (AON). Successive copper(I)-catalyzed azide-alkyne and strain-promoted alkyne-nitrone cycloadditions (SPANC) were utilized for the synthesis.

One-pot construction of carbohydrate scaffolds mediated by metal catalysts.

Owing to the environmental concern worldwide and also due to cost, time and labour issues, use of one-pot reactions [domino/cascade/tandem/multi-component (MC) or sequential] has gained much attention among the scientific and industrial communities for the generation of compound libraries having different scaffolds. Inclusion of sugars in such compounds is expected to increase the pharmacological efficacy because of the possibility of better interactions with the receptors of such unnatural glycoconjugates. In many of the one-pot transformations, the presence of a metal salt/complex can improve the reaction/change the course of reaction with remarkable increase in chemo-/regio-/stereo-selectivity.

Synthesis of Organometallic Oligonucleotides through Oximation with Metalated Benzaldehydes.

A phthaloyl-protected aminooxymethyl--2'-deoxyriboside building block has been prepared and incorporated in the middle of an oligodeoxyribonucleotide. Removal of the phthaloyl protection followed by on-support oximation with either mercurated or palladated benzaldehydes yielded oligonucleotides bearing the respective benzaldoxime metallacycles.

Programmable and Multifunctional DNA-Based Materials for Biomedical Applications.

DNA encodes the genetic information; recently, it has also become a key player in material science. Given the specific Watson-Crick base-pairing interactions between only four types of nucleotides, well-designed DNA self-assembly can be programmable and predictable. Stem-loops, sticky ends, Holliday junctions, DNA tiles, and lattices are typical motifs for forming DNA-based structures.

Oligonucleotides Incorporating Palladacyclic Nucleobase Surrogates.

An oligonucleotide incorporating a palladacyclic nucleobase has been prepared by ligand-directed metalation of a phenylpyridine moiety. This oligonucleotide hybridized with natural counterparts placing any of the canonical nucleobases opposite to the palladacyclic residue. The palladated duplexes had B-type conformation and melting temperatures comparable to those of respective unmodified duplexes with a single mismatch.

Efficient routes toward the synthesis of the D-rhamno-trisaccharide related to the A-band polysaccharide of Pseudomonas aeruginosa.

The present work describes efficient avenues for the synthesis of the trisaccharide repeating unit [α-D-Rhap-(1→3)-α-D-Rhap-(1→3)-α-D-Rhap] associated with the A-band polysaccharide of Pseudomonas aeruginosa. One of the key steps involved 6-O-deoxygenation of either partially or fully acylated 4,6-O-benzylidene-1-thiomannopyranoside by radical-mediated redox rearrangement in high yields and regioselectivity. The D-rhamno-thioglycosides so obtained allowed efficient access to the trisaccharide target via stepwise glycosylation as well as a one-pot glycosylation protocol.

Trichloroisocyanuric acid (TCCA): an efficient green reagent for activation of thioglycosides toward hydrolysis.

Trichloroisocyanuric acid (TCCA), an inexpensive, commercially available, and non-toxic reagent has been used for the activation of thioglycosides toward their hydrolysis to the corresponding hemiacetals in high to excellent yields. The methodology provides a mild reaction condition for dealing with compounds containing acid sensitive functional groups.

Efficient activation of thioglycosides with N-(p-methylphenylthio)-ε-caprolactam-TMSOTf.

N-(p-Methylphenylthio)-ε-caprolactam (1) in combination with trimethylsilyl trifluoromethanesulfonate (TMSOTf) provides an efficient thiophilic promoter system, capable of activating different thioglycosides. Both 'armed' and 'disarmed' thioglycosyl donors were activated for glycosidic bond formation. Notably, this reagent combination works well in reactivity-based one-pot oligosaccharide assembly strategy.

FeCl3 mediated arylidenation of carbohydrates.

Glycosides and thioglycosides based on monosaccharides in reaction with benzaldehyde dimethylacetal or p-methoxybenzaldehyde dimethyl acetal undergo FeCl(3)-catalyzed (20 mol%) regioselective 4,6-O-arylidenation producing the corresponding acetals in high yields. FeCl(3) also mediates acetalation of glycosides and thioglycosides of cellobiose, maltose, and lactose affording the corresponding 4',6'-O-benzylidene acetals, which were isolated after their acetylation in situ with acetic anhydride and pyridine. The combined yields (two steps) of these final products are also high (61-84%).