Solid‐phase synthesis of oligodeoxynucleotides containing 6‐O‐alkylguanosines

High-quality oligodeoxynucleotides having an 6-O-alkyl-2′-deoxyguanosine (alkyl = methyl, ethyl, n-propyl or n-hexyl) residue at a predetermined position can be obtained via a solid-phase approach using the respective 2-cyanoethyl N,N-diisopropylphosphoramidites of 5′-O-(4.4′-dimethoxytrityl)-protected 6-O-alkyl-2′-deoxyguanosines having a free exocyclic amino group, and 5′-O-(4-4′-dimethoxytrityl) N-acyl-protected (i.e., benzoyl and isobutyryl for dC/dA and dG, respectively) 2′-deoxynucleosides.