Synthesis of photolabile 5 '-O-phosphoramidites for the photolithographic production of microarrays of inversely oriented oligonucleotides

The photolabile 3 ' -O-{[2-(2-nitrophenyl)propoxy]carbonyl}-protected 5 ' - phosphoramidites (16-18) were synthesized (see Scheme) for an alternative m ode of light-directed production of oligonucleotide arrays. Because of the characteristics of these monomeric building blocks, photolithographic in si tu DNA synthesis occurred in 5 ' --> 3 ' direction, in agreement with the o rientation of enzymatic synthesis. Synthesis yields were as good as those o f conventional reactions. The resulting oligonucleotides are attached to th e: surface via their 5 ' -termini, while the 3 ' -hydroxy groups are availa ble as substrates for enzymatic reactions such as primer extension upon hyb ridization of a DNA template (see Fig. 2). The production of such oligonucl eotide chips adds new procedural avenues to the growing number of applicati ons of DNA microarrays.