Selective deprotection, hydroxyl groups

Silylation of both the primary and secondary hydroxyl groups is followed by selective deprotection to regenerate the primary hydroxyl group. 

The presence in carbohydrates of multiple hydroxyl groups of similar reactivity makes the chemo- and regio-selective manipulation frequently required quite difficult. For this reason, multistep protection-deprotection approaches are regularly employed in carbohydrate chemistry, and versatile techniques for these transformations are particularly helpful. The following section addresses this aspect, concentrating on the catalytic procedures that have been developed employing zeolites and related siliceous materials. 

Derivatization of functional groups in a natural-product scaffold can also be effectively performed on the solid-phase. An example of this is the synthesis of a small compound collection (27-compounds) based on the tetrahydroquinoline scaffold. A chiral tetrahydroquinoline scaffold was synthesized in solution from 5-hydroxy-2-nitrobenzaldehyde (Scheme 4). The synthesis involved a key asymmetric aminohydroxylation step. This building block was anchored to the solid support with a Wang linker and diversity was introduced by selective deprotection and derivatization of the protected hydroxyl and amino substituents. 

These reaction conditions do not affect most of the other common hydroxyl-protecting groups, and methoxybenzyl groups are therefore useful in synthetic sequences that require selective deprotection of different hydroxyl groups. 4-Methoxybenzyl ethers can also be selectively cleaved by dimethylboron bromide.27... 

---