Altritol nucleic acids (ANAs) are RNA analogues with a phosphorylated D-altritol backbone. The nucleobase is attached at the 2-(S)-position of the carbohydrate moiety. We report that ANA oligomers are superior to the corresponding DNA, RNA, and HNA (hexitol nucleic acid) in supporting efficient nonenzymatic template-directed synthesis of complementary RNAs from nucleoside-5'-phosphoro-2-methyl imidazolides. Activated ANA and HNA monomers do not oligomerize efficiently on DNA, RNA, HNA, or ANA templates.

Nonenzymatic template-directed copying of RNA sequences rich in cytidylic acid using nucleoside 5'-(2-methylimidazol-1-yl phosphates) as substrates is substantially more efficient than the copying of corresponding DNA sequences. However, many sequences cannot be copied, and the prospect of replication in this system is remote, even for RNA. Surprisingly, wobble-pairing leads to much more efficient incorporation of G opposite U on RNA templates than of G opposite T on DNA templates.

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A novel synthesis of silirenes, starting from bis(diazomethyl)silanes 6, is described. The diazo compounds 6 were obtained by treatment of the corresponding triflates with diazomethane. Irradiation of alkyl- or phenyl-substituted 6 in argon matrices or organic glasses at cryogenic temperatures produced 1,1-disubstituted silirenes 7 in high yields. The silirenes were characterized by comparison of the experimental IR spectra with DFT calculations and by their subsequent photochemistry. 1,1-Diphenylsilirene 7c was stable enough in solution below −50 °C to be characterized by 1H and 13C NMR spectroscopy. UV irradiation of silirenes 7 results in ring-opening and formation of ethynylsilanes.

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