... Tetrahedron: Asymmetry. Volume 17, Issue 17, 2 October 2006, Pages 2479–2486. ... lactonization, accomplished by refluxing for 1 h in benzene with a catalytic amount of p-toluenesulfonic acid monohydrate (p-TsOH·H 2 O) to afford N-benzyloxycarbonyl lactone 17 in 90% yield ...