An abnormal deallylation reaction of an l-fucopyranoside

Deallylation of allyl 2,3,4-tri-O-benzyl-l-fucopyranoside in the presence of palladium chloride and cuprous chloride led to an unexpected result. Instead of the expected deallylated product, (2-oxopropyl)-2,3,4-tri-O-benzyl-l-fucopyranoside was obtained.