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The electrochemical preparation of nanostructured titanium clusters is possible by using B titanium sacrificial anode as the metal source and tetrabutylammonium bromide in THF as the electrolyte and stabilizer. Transmission electron mi-croscopy shows the presence of spherical 3.0-nm-sized particles. THF solutions of these Ti clusters induce olefin-forming McMurry-type coupling of aldehydes and ketones.

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The amino functions of the common 2'-deoxyribo-and ribonucleosides were blocked by the (2-cyanoethoxy)carbonyl group on treatment with 2-cyanoethyl carbonochloridate (5) or 1-[(2-cyanoethoxy)carbonyl]-3-methyl-1H-imidazolium chloride (6) leading to 7, 18, 8, 19, 9, and 20. In 2'-deoxyguanosine, the amide group was additionally blocked at the O 6 position by the 2-cyanoethyl ( 3 27) and 2-(4-nitrophenyl)ethyl group ( 3 31, 32). Comparative kinetic studies regarding the cleavage of the ce/ceoc and npe/npeoc group by b-elimination revealed valuable information about the ease and sequential deprotection of the various blocking groups at different sites of the nucleobases. Besides the 5'guanosine analog 40 is recommended as building block for oligo-2'-deoxyribonucleotide synthesis. Introduction. ± The development of the 2-(4-nitrophenyl)ethyl (npe) and [2-(4-nitrophenyl)ethoxy]carbonyl (npeoc) groups as versatile protective groups for nucleobases [2], phosphate [3] [4], and phosphite functions [5] [6] broadened the strategy of nucleoside and nucleotide protection in oligonucleotide synthesis universally. The great advantange of these groups is their high stability under acidic and mild basic hydrolytic conditions as, for example, in the presence of ammonia and amines in MeOH, dioxane, or H 2 O, whereas their cleavage can easily and quantitatively be achieved by 1,8-diazabicyclo[5.4.0]undecene (DBU) in aprotic solvents by a b-elimination process.The 2-cyanoethyl (ce) group [7] [8] is the most common blocking group for the phosphate and phosphite moiety of nucleotides, but strangely enough, the ce and its corresponding (2-cyanoethoxy)carbonyl (ceoc) group have not been applied for base protection in analogy to the npe/npeoc couple. Several years ago, we [9] [10] developed the ce/ceoc strategy as an alternative approach for the synthesis of special oligonucleotides. Details about the nucleobase protection by the ce and ceoc group will now be reported since N-{[(2-cyanoethoxy)carbonyl]oxy}succinimide has recently been described as a new reagent for protection of amino groups in oligonucleotides [11]. We protected the amino group in cytidine, adenosine, and guanosine as well as in the corresponding 2'-deoxynucleosides with the ceoc group and utilized the ce group