AN EXPEDITIOUS ROUTE TO METHYLPHOSPHONATE ANALOGS OF DNA

Protection of the exocyclic amino groups of both nucleobases adenine a nd guanine with the N,N-dimethylformamidine and cytosine with the isob utyryl group presents a convenient and economical N-protective-group-s trategy for the solid-phase synthesis of DNA fragments containing meth ylphosphonate linkages at predetermined locations. Thus, the post-synt hesis removal of the N-protective groups with hydrazine hydrate (16 h at 20-degrees-C) afforded immobilized fragments, which were then cleav ed from the solid support and deprotected at the phosphorus by treatme nt with ammonia in methanol (2 h at 20-degrees-C) to yield high-qualit y products.