Nucleoside derivatives, and their use in oligonucleotide synthesis

A method of oligonucleotide synthesis, comprising:

• successive adding nucleotides starting with a first nucleoside attached to a solid support, wherein each addition of a nucleotide comprises the cleavage of the protecting group for the 5′-OH function of the nucleotide or of the preceding nucleoside, and the coupling of the nucleotide to be added, to the deprotected 5′-OH function,
• wherein at least one of addition of a nucleotide is carried out with a nucleoside derivative represents by the formula (I), and wherein the cleavage of the protecting group for the 5′-OH function of the nucleotide represented by formula (I) is carried out by an electrochemical reaction,
• wherein
• R1 represents:
• an electrolabile group represented by formula (IIa):
• in which R4 represents an NO2 group and R5 represents a hydrogen atom, a linear or branch C1 to C10 alkyl group, a group
• or a group
• where R′ represents a linear or branched C1 to C10 alkyl group, or a group —O—R′ where R′ represents a linear or branched C1 to C10 alkyl group, or alternatively
• an electrolabile group represented by formula (IIb):
• in which one of the groups Ra, Rb or Rc represents a phenyl group, or a substituted phenyl group, and the other two represent hydrogen atoms,
• R2 represents a hydrogen atom, or a phosphoramidite, phosphonate or phosphotriester group;
• R3 represents a hydrogen atom, a hydroxyl radical, a substituted hydroxyl radical or a halogen,
• B represents a radical derived from a purine or a pyrimidine base represented by one of the following formulae:
• wherein R6 represents a protecting group for the amine function, other than an isobutyryl or phenylpropionyl group, represented by one of the formulae (VII), (VIII) or (IX) below:
• in which R9 and R11, which may be identical or different, represent a hydrogen atom, or a C1-C10 alkoxy or alkyl group, R12 represents a linear or branched C1-C10 alkyl radical, and R10 is represented by the formula:
• R7 represents a protecting group for the amine function, other than a phenylpropionyl group, represented by one of the formulae (VII), (VIII) or (IX) defined above;
• R8 represents a protecting group for the amine function, other than an isobutyryl, phenylpropionyl or phenoxyacetyl group, corresponding to one of the formulae (VII), (VIII) or (IX) defined above;
• with the exception of the derivatives in which R1 is an electrolabile group represented by formula (IIa) in which R4 represents an NO2 group and R5 a hydrogen atom, and B is represented by formula (III).