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Conjugation of molecules or proteins to oligonucleotides can improve their functional and therapeutic capacity. However, such modifications are often limited to the 5′ and 3′ end of oligonucleotides. Herein, we report the development of an inexpensive and simple method that allows for the insertion of chemical handles into the backbone of oligonucleotides. This method is compatible with standardized automated solid‐phase oligonucleotide synthesis, and relies on formation of phosphoramidates. A unique phosphoramidite is incorporated into a growing oligonucleotide, and oxidized to the desired phosphoramidate using iodine and an amine of choice. Azides, alkynes, amines, and alkanes have been linked to oligonucleotides via internally positioned phosphoramidates with oxidative coupling yields above 80 %. We show the design of phosphoramidates from secondary amines that specifically hydrolyze to the phosphate only at decreased pH. Finally, we show the synthesis of an antibody‐DNA conjugate, where the oligonucleotide can be selectively released in a pH 5.5 buffer. [ABSTRACT FROM AUTHOR]

A method for automated solid‐phase synthesis of oligo(disulfide)s was developed. It is based on a synthetic cycle comprising removal of a protecting group from a resin‐bound thiol followed by treatment with monomers containing a thiosulfonate as an activated precursor. For ease of purification and characterization, the disulfide oligomers were synthesized as extensions of oligonucleotides on an automated oligonucleotide synthesizer. Six different dithiol monomer building blocks were synthesized. Sequence‐defined oligomers of up to seven disulfide units were synthesized and purified. The sequence of the oligomer was confirmed by tandem MS/MS analysis. One of the monomers contains a coumarin cargo that can be released by a thiol‐mediated release mechanism. When the monomer was incorporated into an oligo(disulfide) and subjected to reducing conditions, the cargo was released under near‐physiological conditions, which underlines the potential use of these molecules in drug delivery systems. [ABSTRACT FROM AUTHOR]

The unique structural motifs and self-recognition properties of DNA can be exploited to generate self-assembling DNA nanostructures of specific shapes using a 'bottom-up' approach'. Several assembly strategies have been developed [...]

Study develops a general approach to N-arylation and N-alkenylation of all five DNA/RNA nucleobases at the nitrogen atom normally attached to the sugar moiety in DNA or RNA. A 4-alkylthio-substituted pyrimidin-2(1H)-one served as both a cytosine and a uracil precursor and was N-arylated and N-alkenylated in high yields.

Density functional theory calculations were carried out for the adsorption of a chiral molecule, (S)- and (R)-HSCH2CHNH2CH2P(CH3)(super 2), on a chiral surface. The S-enantiomer is found to bind more strongly than the R-enantiomer by 8.8 kJ/mol, evidencing that the chiral nature of the kink sites at the Au surface leads to enantiospecific binding.

The first example of a catalytic 1,3-dipolar cycloaddition reaction with inverse-electron demand of aromatic nitrones with vinyl ethers is reported. The reaction used chiral aluminum complexes as catalysts and gave isoxazolidines in high yield, with regio-, diastereo- and enantioselectivity. The calculated structure of the nitrone coordinated to the (R)-BINOL-AlMe catalyst provided explanation on how the nitrone coordinates to the catalyst and how the alkene approaches the activated nitrone. The reaction led to exo-isoxazolidines in good yield with endo:exo ratios less than 5:greater than 95 and with enantiomeric excess of up to 97%.

Research was conducted to demonstrate that molecular sieve (MS) was a fundamental part of the reaction in which the magnesium(II)-(R,R)-bisoxazoline-alkenoyloxazolidinone intermediate is highly likely bound to the surface of the MS. Results confirmed the importance of MS in catalytic asymmetric chemistry as proven by the dependence of enantioselective 1,3-dipolar cycloaddition of alkenes with nitrones catalyzed by chiral magnesium(II)-bisoxazoline complexes. Also proven was the influence of additives agents on stereoselectivity.

Asymmetric 1,3-DC reactions of a series of dipoles with alkenes are necessary in the construction of five-membered rings. The application of 1,3-DC reaction, which is also suitable in the synthesis of optically active target molecules, is noticeable in products formed from dipoles such as nitrones, nitrile oxides and azomethine ylides. The asymmetric-metal catalyzed 1,3-DC reactions are necessary in analyzing metal catalysis and optically active compounds.