Syntheses of DNA duplexes containing a C-C interstrand cross-link

Short DNA duplexes that contain a (NC)-C-4-ethyl-(NC)-C-4 interstrand cross -link were prepared on controlled pore glass supports using a DNA synthesiz er. The C-C cross-link was introduced via a convertible nucleoside on the s upport or by using a protected C-C cross-link phosphoramidite. An orthogona l protection scheme allowed selective chain growth in either a 3' --> 5' or 5' --> 3' direction. The cross-linked duplexes were purified by HPLC and c haracterized by MALDI-TOF mass spectrometry and/or by enzymatic digestion.