Conceptual "Heat-Driven" Approach to the Synthesis of DNA Oligonucleotides on Microarrays

: The discovery of deoxyribonucleoside cyclic N‐acylphosphoramidites, a novel class of phosphoramidite monomers for solid‐phase oligonucleotide synthesis, has led to the development of a number of phosphate protecting groups that can be cleaved from DNA oligonucleotides under thermolytic neutral conditions. These include the 2‐(N‐formyl‐N‐methyl)aminoethyl, 4‐oxopentyl, 3‐(N‐tert‐butyl)carboxamido‐1‐propyl, 3‐(2‐pyridyl)‐1‐propyl, 2‐[N‐methyl‐N‐(2‐pyridyl)]aminoethyl, and 4‐methythiobutyl groups. When used for 5′‐hydroxyl protection of nucleosides, the analogous 1‐phenyl‐2‐[N‐methyl‐N‐(2‐pyridyl)]aminoethyloxycarbonyl group exhibited excellent thermolytic properties, which may permit an iterative “heat‐driven” synthesis of DNA oligonucleotides on microarrays. In this regard, progress has been made toward the use of deoxyribonucleoside cyclic N‐acylphosphoramidites in solid‐phase oligonucleotide syntheses without nucleobase protection. Given that deoxyribonucleoside cyclic N‐acylphosphoramidites produce oligonucleotides with heat‐sensitive phosphate protecting groups, blocking the 5′‐hydroxyl of these monomers with, for example, the thermolabile 1‐phenyl‐2‐[N‐methyl‐N‐(2‐pyridyl)]aminoethyloxycarbonyl group may provide a convenient thermo‐controlled method for the synthesis of oligonucleotides on microarrays.