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 o pen-chain 1,2,3-triols is demonstrated in the highly selective terminal der ivatisation of D-mannitol and an antiviral sialic acid derivative. Protecti on, derivatisation and deprotection are carried out in a single pot, yieldi ng analytically pure products in moderate yield, without the need for chrom atography or formal recrystallisation steps. In both classes of compound, t he selectivity of protection is found to be complementary to existing metho ds, providing access to relatively uncommon 1,6-diesters and the 1,6-bis(be nzyl ether) of D-mannitol, and 9-o-acylsialic acid derivatives.