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2′-O-(N-(Aminoethyl)carbamoyl)methyl (2′-O-AECM)-modified oligonucleotides (ONs) and their mixmers with 2′-O-methyl oligonucleotides (2′-OMe ONs) with phosphodiester linkers as well as with partial and full phosphorothioate (PS) inclusion were synthesized and functionally evaluated as splice-switching oligonucleotides in several different reporter cell lines originating from different tissues. This was enabled by first preparing the AECM-modified A, C, G and U, which required a different strategy for each building block. The AECM modification has previously been shown to provide high resistance to enzymatic degradation, even without PS linkages. It is therefore particularly interesting and unprecedented that the 2′-O-AECM ONs are shown to have efficient splice-switching activity even without inclusion of PS linkages and found to be as effective as 2′-OMe PS ONs. Importantly, the PS linkages can be partially included, without any significant reduction in splice-switching efficacy. This suggests that AECM modification has the potential to be used in balancing the PS content of ONs. Furthermore, conjugation of 2′-O-AECM ONs to an endosomal escape peptide significantly increased splice-switching suggesting that this effect could possibly be due to an increase in uptake of ON to the site of action.

A novel, N-(pyrrolidinyl-2-methyl)glycine-based (Pmg-based) PNA is introduced. The synthesis of the backbone was accomplished in good yield, starting from prolinol. Thymine (S)- and (R)-Pmg and adenine- and cytosine-derived (R)-Pmg monomers were prepared. Five different fragments − two with either the (R) or the (S) isomer of the thymine Pmg monomer, two oligomers with two consecutive (R)- or (S)-thymine Pmg units, and fully modified (R)-Pmg decamer − were assembled on a solid support. UV thermal melting experiments with complementary DNA and RNA were performed in order to determine the effects of conformational restriction, steric hindrance, and chirality on the duplex stability. It was found that the (R)-Pmg-containing PNAs bound better to DNA and RNA than those containing the (S)-Pmg isomer and that both (S)- and (R)-Pmg-containing PNAs preferentially bound to complementary RNA with a selectivity higher than that of 2-(aminoethyl)glycine (Aeg) PNA. However, even (R)-Pmg-containing oligomers showed poorer duplex stability than nonmodified Aeg-PNA, while no detectable binding either to the DNA or to the RNA was observed with the fully modified (R)-Pmg decamer. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A novel, N-(pyrrolidinyl-2-methyl)glycine-based (Pmg-based) PNA is introduced. The synthesis of the backbone was accomplished in good yield, starting from prolinol. Thymine (S)- and (R)-Pmg and adenine- and cytosine-derived (R)-Pmg monomers were prepared. Five different fragments − two with either the (R) or the (S) isomer of the thymine Pmg monomer, two oligomers with two consecutive (R)- or (S)-thymine Pmg units, and fully modified (R)-Pmg decamer − were assembled on a solid support. UV thermal melting experiments with complementary DNA and RNA were performed in order to determine the effects of conformational restriction, steric hindrance, and chirality on the duplex stability. It was found that the (R)-Pmg-containing PNAs bound better to DNA and RNA than those containing the (S)-Pmg isomer and that both (S)- and (R)-Pmg-containing PNAs preferentially bound to complementary RNA with a selectivity higher than that of 2-(aminoethyl)glycine (Aeg) PNA. However, even (R)-Pmg-containing oligomers showed poorer duplex stability than nonmodified Aeg-PNA, while no detectable binding either to the DNA or to the RNA was observed with the fully modified (R)-Pmg decamer. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The selective monohalogenation of dihexylsilane by a number of oxidants was studied. The most selective oxidant was found to be N -bromosuccinimide, NBS, yielding products of monobromination with greater than 50:1 selectivity. Various degrees of monoselectivity were found in the bromination of other differentially substituted dihydro- and trihydrosilanes by NBS.

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