The synthesis of compound 3a is illustrated in Sch. 1. Tetrahydrothiophene??3??one (1a, 101 g, 1.05 mol) was protected as the diethyl ketal using triethyl orthoformate in the presence of para??toluenesulfonic acid and then directly oxidized with aqueous hydrogen peroxide in the presence of a catalytic amount of sodium tungstate and sodium acetate. The crystalline product was isolated by filtration and washed with water. This one pot process yielded 195 g ...