Oligonucleotide analogues with a nucleobase-including backbone: Part 6 2-deoxy-D-erythrose-derived phosphoramidites: Synthesis and incorporation into14-mer DNA strands

Two modified DNA 14-mers have been prepared, containing either a 2-deoxy-D- erythrose-derived adenosine analogue carrying a C(8)-CH2O group (deA*). or a 2-deoxy-D-erpthrose-derived uridine analogue, possessing a C(6)-CH2O grou p (deU*). These nucleosides are linked via a phosphinato group between O-C( 3') (deA* and deU*) and O-C(5') of one neighbouring nucleotide, and between C(8)-CH2O (deA*),or C(6)-CH2O (deU*) and O-C(3') of the second neighbour. N-6-Benzoyl-9-(beta -D-erythrofuranosyl)adeine (3) and 1-(beta -D-erythrofu ranosyl)uracil (4) were prepared from D-glucose, deoxygenated at C(2'), and converted into the required phosphoramidites 1 and 2. The modified tetrade camers 31 and 32 were prepared by solid-phase synthesis. Pairing studies sh ow a decrease in the melting temperature of 7 to 8 degrees for the duplexes 31 30 and 32 29, as compared to the unmodified DNA duplex 29 30. A compari son with the pairing properties of tetradecamers similarly incorporating de oxyribose- instead of the deoxyerythrose-derived nucleotides evidences that the CH2OH substituent at C(4') has no significant effect on the pairing.