O-Nitrobenzyl ether

The o-nitrobenzyl and p-nitrobenzyl ethers can b prepared and cleaved by many of the methods described for benzyl ethers. The p-nitrobenzyl ether is also prepared from an alcohol and p-nitrobenzyl alcohol (trifluoroacetic anhydride, 2,6-lutidine, CH2CI2, 67% yield). In addition, the o-nitrobenzyl ether can be cleaved by irradiation (320 nm, 10 min, quant, yield of carbohydrate " 280 nm, 95% yield of nucleotide ). The p-nitrobenzyl ether has been cleaved by electrolytic reduction (—1.1 V, DMF, R4N X, 60% yield) and by reduction with Na2S204 (pH 8-9, 80-95% yield). These ethers can also be cleaved oxidatively (DDQ or electrolysis) after reduction to the aniline derivative. ... 

H. Sajiki, H. Kuno, and K. Hirota, Tetrahedron Lett., 38, 399 (1997). o-Nitrobenzyl Ether o-N02-QH4CH20Ar (Chart 4)... 

A class of photolabile linkers has been developed to circumvent the use of silyl ethers as linkers and allow for the use of temporary silyl protecting groups.34,35 Photolabile linkers, such as 2, often involve the use of o-nitrobenzyl ether groups. This functional group is stable to a variety of conditions however, cleavage from the polymer support is often slow and... 

An o-nitrobenzyl ether.can be cleaved by photolysis. In tyrosine this avoids the use of acid-catalyzed cleavage and the attendant conversion to 3-beilsyltyrosine.1 (Note that this unwanted conversion can also be suppressed by the addition of thioanisole see section on benzyl ether cleavage.)... 

Introduction of substituents into the aromatic ring makes the benzylic system prone to further deblocking methods. Thus, o-nitrobenzyl ethers, available from o-nitrobenzyl bromide, are cleaved photolyti-caiiyi38 and the mono- and di-methoxybenzyl groups (Mpm and Dmpm) are removable by oxidation... 

Photolysis of o-Nitrobenzyl Derivatives - The cleavage of o-nitrobenzyl derivatives is one of the relatively few classes of photofragmentations in which the two fragments can both bear complex functionality. The protection of alcohols as o-nitrobenzyl ethers is well known, and provides a photochemical method of deprotection, but other applications include the design of photoclea-vable polymers and photochemically active links for molecules synthesized on polymer beads. 

The second activation cascade indicated in Scheme 7-70 for the Nicolaou dynemicin model systems was demonstrated through the triggering of the phenol derivative 352, cleanly produced by photolytic deprotection of the o-nitrobenzyl ether 351 (Scheme 7-74) (119, 120]. Tlreatment of 352 with nucleoplules (e.g., EtOH, EtSH, -PrNH2) provided the aromatization... 

Protection of Hydroxyl Groups. Photolabile 2 -0-(o-nitrobenzyl) derivatives of various ribonucleotides as well as dinucleotides have been synthesized, and their subsequent photodeprotections, which yield the corresponding alcohols, examined (eq 11). Protection of the anomeric hydroxyl functionality of 2-deoxy-D-ribofuranose has been accomplished using o-NBA (eq 12). This protective group is quite stable to acidic conditions, and has proven invaluable in the synthesis of abasic oligonucleotides. Similar conditions are employed in the synthesis of bis(o-nitrobenzyl) ethers. ... 

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