Linkers Based on o-Nitrobenzyl

Various o-nitrobenzyl-based linkers are outlined in Fig. 14, together with the acyl 

The linker 155 [173] has recently been further optimized so that it is stable towards add, base, and Lewis add/amine combinations [176]. 

The conditions for the photolytic deavage to mediate release of the products 

Alkylation of vanillin 158 with methyl 4-bromobutyrate and subsequent nitration afforded 159. Addition of the methyl group to the aldehyde was performed with the commercially available AlMes to yield 160 this could be crystallized directly from the crude reaction mixture after the three steps. After hydrolysis, the corresponding acid may be attached to a hydroxy-modified support as an ester. Acylation then results in the desired construct 157. 

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