H-Ala-Ala-Ala-OME acetate

Protecting group chemistry is essential for various organic transformation and polymerization processes. In particular, conventional anionic ring-opening polymerization (AROP) often requires proper protecting group chemistry because it is typically incompatible with most functional groups due to the highly basic and nucleophilic conditions. In this context, many functional epoxide monomers with proper protecting groups are developed, including the acetal group as a representative example. Since the early introduction of ethoxyethyl glycidyl ether, there is significant development of acetal-based monomers in the polyethers. These monomers are now utilized not only as protecting groups for hydroxyl groups under AROP conditions but also as pH-responsive moieties for biomedical applications, further expanding their utility in the use of functionalized polyethers. Recent progress in this field is outlined from their synthesis, polymerization, and biomedical applications.

In this report, we demonstrate that visible light photoactivation of 6-bromo-2-naphthol facilitates the photoacid-catalyzed acetalization of carbonyls with alcohols. We also demonstrate that 2-naphthol when coupled to a photosensitizer provides acetals from electron-deficient aldehydes. In addition, the S1 excited state pKa for 6-bromo-2-naphthol in water was determined and shown to have increased excited-state acidity relative to 2-naphthol.

This review details the isolation, biosynthesis, biological activity and synthesis of spiroacetals from the myxobacterium Sorangium cellulosum. The strategies utilised to access the challenging structures and stereochemistry of these natural products are highlighted.