3,3ʹ,5,5ʹ-Tetramethoxybenzoin: a forgotten photolabile protecting group.

Although reported several decades ago, 3,3ʹ,5,5ʹ-tetramethoxybenzoin esters have not been used as a common photolabile protecting group, contrary to their unsymmetrical 3ʹ,5ʹ-dimethoxybenzoin analogues. While the properties of the latter are superior, their tedious synthesis and chemical instability represent a drawback. In this article, we describe a reliable synthetic access to the symmetrical tetramethoxybenzoin derivatives, and show that their photochemical behaviour remain interesting, in particular chromatically orthogonality with respect to nitroveratryl esters. [ABSTRACT FROM AUTHOR]