Protection/deprotection chemistry

The parent spacer, 4-hydroxybutanoic acid, spontaneously undergoes loss of water under acidic or basic conditions to give 4-butyrolactone. To prevent cyclization when the spacer is coupled to methoprene, both the hydroxyl and carboxyl functions had to be protected and selectively deprotected. The methods used are summarized in Figure 2. The protection/deprotection chemistry described was originally developed for use in the field of peptide synthesis. 

The direct synthesis of functional, self-assembling copolymers in aqueous media under mild conditions without protection/deprotection chemistry steps, however, remains a current challenge that focuses research efforts on developing stimuli-responsive delivery systems such as micelles... 

In addition to the alkene-functionalized polymer approach of making side-chain functionalized polymer, other approaches have also been reported. For example, based on the protection-deprotection chemistry of ortho-nitrobenzyl moiety, Barner-Kowollik and coworkers investigated light-triggered release of thiols at ambient temperature and developed a novel method to modify functionalization... 

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