New Photolabile Protecting Groups in Nucleoside and Nucleotide Chemistry—Synthesis, Cleavage Mechanisms and Applications

Intramolecular Sensitization of Photocleavage of the Photolabile 2‐(2‐Nitrophenyl)propoxycarbonyl (NPPOC) Protecting Group: Photoproducts and Photokinetics of the Release of Nucleosides

“…[15,16] It is of the onitrobenzyl-type in which cleavage occurs at the benzylic carbon and the leaving moiety is an aromatic o-nitrosocarbonyl compound. [17] In photoremovable protecting groups involving the 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) group, which was introduced by Pfleiderer and co-workers, [18][19][20] cleavage is due to b elimination, and formation of the reactive and problematic nitroso byproduct [21] can be suppressed by using suitable reaction conditions (Scheme 1). [22] This is probably the reason why chips of higher quality result when using the NPPOC group.…”

Production by quantitative photolithographic synthesis of individually quality checked DNA microarrays

“…They differ especially by an additional methylene moiety on the α-carbon, which is responsible for a completely different photocleavage mechanism. From studies in solution it was concluded that a photoinduced β-elimination process was the favoured pathway for the NPPOC group (12). Therefore, we proposed that the presence of aprotic basic solutions during irradiation might enhance photoremoval of NPPOC moieties.…”

“…For chip production with NPPOC phosphoramidites, irradiation was initially performed in the presence of 10% water in methanol known from in-solution studies (12). However, only DNA arrays of low quality were obtained (Fig.…”

“…1) being a particularly promising candidate. Initial studies in aqueous methanolic solution showed that the NPPOC group could be very effectively removed from 5′-O-protected thymidine derivatives by irradiation at 365 nm (12).…”

More Efficient Photolithographic Synthesis of DNA-Chips by Photosensitization

“…The weak absorptivity of these compounds leads to principal limitations of their light sensitivity. Since they have photoreactive triplet states, however, this problem can be overcome by introducing a triplet sensitizer that efficiently absorbs the light and transfers the electronic energy to the reactive protecting group.The sensitized photodeprotection was studied in detail for the o-nitrophenyl-2-propoxycarbonyl (NPPOC) group [3] where the photo cleavage occurs via b-elimination of the corresponding nitrostyrene derivative as shown in the scheme. The first step of this reaction is photochemically initiated intramolecular H-atom transfer from the a-position to the nitro group whereby an aci-nitro compound is formed [3] .…”