Attachment to the Phosphate Bridge

The use of special CPG-phosphoramidites with glycerol linkers has been proposed to test different 3 -modifications of an oligonucleotide of identical sequence. After solid-phase synthesis, glycerol esters are cleaved and oxidized. The resulting acid or aldehyde may be further re- 

As pointed out in section 9.6.5, insertion of 3 -0-(N,N-diisopropylamino)methoxyphos-phine nucleotide monomers and subsequent amidation using 1,5-diaminopentane/iodine leads to aminoalkylated phosphoramidates, which may act as linkers for functional moieties (Fig. 33). 

However, such modifications are not suited in sequencing and amplification experiments in which the 3 -hydroxy group of the oligonucleotide has to remain free. Both 5-alkylpyrimi-dines and 5 - and 2 -modifications of sugars (2 -alkoxy-, 2 -deoxy-2 -alkylamino- and 2-0-aminoalkyl-linkers) may be applied. 

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