Phenylboronic acid as a labile protective agent: The selective derivatisation of 1,2,3-triols

The ability of phenylboronic acid to act as a labile protective agent for open-chain 1,2,3-triols is demonstrated in the highly selective terminal derivatisation of D-mannitol and an antiviral sialic acid derivative. Protection, derivatisation and deprotection are carried out in a single pot, yielding analytically pure products in moderate yield, without the need for chromatography or formal recrystallisation steps. In both classes of compound, the selectivity of protection is found to be complementary to existing methods, providing access to relatively uncommon 1,6-diesters and the 1,6-bis(benzyl ether) of D-mannitol, and 9-o-acylsialic acid derivatives.