A stereoregular all-(Sp)-boranophosphate oligodeoxyribonucleotide (BH3(-)-ODN) 15-mer was synthesized using an enzymatic approach. The BH3(-)-ODN formed a hybrid with the complementary RNA 15-mer and induced RNase H hydrolysis of the RNA strand at ODN concentrations as low as 10 nM at 37 degrees C, but with a lower efficiency than that of its natural phosphodiester analogue.