Synthesis and intramolecular transesterifications of pivaloylated methyl α-d-galactopyranosides

Selective pivaloylations of methyl α-d-galactopyranoside have been studied under various reaction conditions. Partially pivaloylated products were submitted to additional acetylations. The structures were established by 1H and 13C NMR spectroscopies. Both, 2,6- and 3,6-dipivalates underwent intramolecular cyclization in neutral conditions (phosphate buffered saline, pH 7.2) to give a stable 2,3-orthoacid with a parallel 6→4 migration of the pivaloyl group.