DIRECT, SOLID-PHASE ASSEMBLY OF DIHYDROPYRROLOINDOLE PEPTIDES WITH CONJUGATED OLIGONUCLEOTIDES

A new controlled pore glass (CPG) support is described that allows for the direct synthesis of oligonucleotide derivatives carrying a minor groove binding (MGB) agent at the 3'-terminus. The MGB consisted of th ree repeating 1,2-dihydro-3H-pyrrolo[2,3-e]indole-7-carboxylate (DPI) subunits. The DPI trimer (DPI3) was prepared directly on the CPG suppo rt using repeated addition of the DPI subunit. The subunit was protect ed at the N-3-position with tert-butyloxycarbonyl residue and activate d at the 7-carboxy residue by esterification with the 2,3,5,6-tetraflu orophenyl group. A linker, which provided the starting point for oligo nucleotide synthesis, was introduced by reaction of the terminal N-3 w ith p-nitrophenyl 4-[bis(4-methoxyphenyl)phenylmethoxy]butyrate. When used as a support for oligonucleotide synthesis, this modified CPG gav e the desired 3'-DPI3-octathymidylate [(dTp)(8)-DPI3] conjugate in goo d yield. This conjugate formed hyperstabilized complexes with compleme ntary polyribo- (T-max = 35 degrees C) and polydeoxyriboadenylic (T-ma x = 69 degrees C) acids. In contrast to the N-carbamoyl derivative rep orted earlier by us, it demonstrated higher cooperativity of melting t ransitions.