Amines photolabile linkers

Harren [24] provided another example of an a-substituted photolabile linker (12) and anchored it to an aminopropylsiloxane-grafted controlled pore glass (amino CPG). It had a longer tether and sterically less bulky amine. An Fmoc-Gly photolysis test resulted in a 77% yield after 2h of irradiation at 350 nm (Scheme 17.8). 

The application of a triazene motif to the development of a photolabile linker was reported by Enders in 2004 [63]. The reaction of a secondary amine with polymer-bound diazonium salt 45 produced the triazene moiety 46. It was stable to a wide range of non-acidic conditions, suitable for other organic reactions. Photocleavage was carried out with 355 nm UV laser irradiation (3co Nd-YAG) in methanol-diethyl ether (Scheme 17.22). 

An application of a related resin involves the synthesis of oligonucleotides via photolabile carbonate and carbamate anchors [230]. Photocleavable al-koxylbenzyl safety-catch solid supports Sr (Table 5) have been prepared [231,232]. Carboxylic acids were esterified by reaction with the secondary alcohol function of 5r and alcohols and amines could be attached via carbonate and carbamate derivatives, respectively. Unlike many previously reported photolabile linkers, these anchors were stable to irradiation with sunlight. In each case, product release was effected by treatment with mercuric chloride to remove the safety catch followed by irradiation with light of wavelength 350 nm, which leaves a benzofuran by-product tethered to the resin. 

More recently. Erase has also introduced the T2 triazene linker unit. The T2 linkers are most commonly used for immobilization of amines (and other nitrogenous compounds). As their T1 counterparts, the T2 linkers have also proven robust linkers for SPOS. For example, amines can be cleaved by treating with TFA (Table 1.8, Entry 1), while treatment with trimethylsilyl chloride is typically used when preparing (and cleaving) ureas (Table 1.8, Entry 2) or amides (Table 1.8, Entry 3). Alternatively, the T2 linker can also behave as a photolabile linker unit and photolytic cleavage (X, = 355 nm) by Enders et al. was used as a strategy to release amines (Table 1.8, Entry 4). ... 

Resin Double-Loading, Attachment of Photolabile Linker, Encoding and Incorporation of Ra Amine Synthons... 

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