2-Cyanoethyl group

The 2-cyanoethyl group was cleaved from an aromatic sulfide with K2C03/NaBH4 (DMF, 135°, 70% yield). ... 

DBU, CH3CN, 140 s. The 2-(4-nitrophenyl)ethyl (Npe) phosphate protective group and the 2-(4-nitrophenyl)ethoxycarbonyl (Npeoc) group are stable to these conditions, but the cyanoethyl group is not. 

TMSCl, DBU, CH2CI2, 25°. The presence of TMSCl allows for complete deprotection of a biscyanoethyl phosphate. Without TMSCl, only one cyanoethyl group was cleaved. ... 

This is a vinylogous analogue of the cyanoethyl group that is removed by... 

Baumeister et al. [116] described the crystal structure of 4-(2-cyanoethyl)-cyclohexyl 4-n-pentylcyclohexanecarboxylate. The almost fully stretched molecule is only distorted by the gauche conformation of the cyanoethyl group. The crystal packing is characterised by a discrete layered arrangement with an antiparallel orientation of neighbouring molecules. With respect to intermolecular interactions, no remarkable contacts between the cyano groups can be observed. 

The 5 -dimethoxytrityl or /5-cyanoethyl group of the fully protected mononucleotide could then be selectively cleaved. 

Of course, the product does not have a phosphate linker between the two nucleosides, and phosphorus is still in the wrong oxidation state. This is remedied by oxidation of the dinucleotide phosphite to a phos-photriester using iodine. We now have the required phosphate linker, though it is still protected with the cyanoethyl group. This is retained at this stage. 

It then remains to remove protecting groups and release the product from the support. All of these tasks, except for the removal of the dimethoxytrityl group, are achieved by use of a single deprotection reagent, aqueous base (ammonia). The cyanoethyl groups are lost from the phosphates by base-catalysed elimination, and amide protection of the bases is removed by base-catalysed hydrolysis. The latter process also achieves hydrolysis of the succinate ester link to the support. 

In an analogous way, secondary amines can be protected through attachment of / -cyanoethyl or a similar function. The cyanoethyl group undergoes facile Cope elimination from initially formed A-oxide (e.g. 137, equation 91) thus giving the corresponding hydroxylamine 138 in a good yield . ... 

One astute way to obtain macrocyclic systems with TTF is the stepwise method of deprotection/alkylation of cyanoethyl-protected TTF-thiolates. With this method molecular units can be built but with the precaution of preserving one cyanoethyl group in order to be able to iteratively proceed with the oligomerization. Combining such units, larger units can be produced. An example of a TTF dendrimer containing 21 TTFs is shown in Fig. 2.15 (Christensen et al, 1998). Here only the main philosophy of the synthesis is discussed. 

Cyanoethyl groups can be conveniently reduced to 2-aminoethyl groups using Raney nickel-hydrogen to give 2-aminoethyl-substituted ortho esters [149] (Eq. 49). 

Remove protecting groups from bases Remove cyanoethyl groups from phosphates Cleave chain from silica support... 

The materials prepared by this route can be farther reacted to produce other catalytically active species. For example the cyanoethyl group can be hydrolysed using 50% sulfuric acid at 150 °C to produce the carboxylic acid. This can be further converted to the peracid, as shown in Figure 2[10],... 

Solid-phase synthesis is usually done on a silica support with a covalently attached succinamide as shown in Eq. 5-25. The first nucleotide at the 3 end of the chain to be synthesized is attached by an ester linkage to the bound succinamide (step a, Eq. 5-25). The 5 -protecting group is removed in step b and the 5 -OH reacts with the activated phosphine of the second nucleotide (step c, Eq. 5-25). Steps b and c are then repeated as often as necessary to complete the chain. The finished polynucleotide can be removed from the solid support, the cyanoethyl groups removed... 

Tertiary amine oxides can be converted into TV-hydroxy secondary amines provided that one of the TV-substituents can be selectively eliminated. This procedure has been applied to the synthesis of secondary A-hydroxy-a-amino acids 34 from the corresponding secondary a-amino acids using the /V-cyanoethyl group for transient protection of the secondary amine (Scheme 10) J40l More recently, direct oxidation with 2,2-dimethyldioxirane of a primary amine has been described for H-L-Val-OMe (82% yield) and H-L-Phe-OMe (54% yield))13 The reaction proceeds smoothly without epimerization, but no experimental details have been reported. 

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