Synthesis and stability of the cyclic sulfamidate of N-trityl-L-serine methyl ester

The title compound 12, prepared in three steps from L-serine methyl ester, is thermally stable <50 °C; the formation of the cyclic sulfamidite 9, rather than acyclic products, in the reaction of thionyl chloride with vic-amino alcohol 7 is far more dependent on reaction conditions than with less crowded molecules.