Selective protection of carbonyl groups as acetals is essential step in modern organic chemistry as it is often necessary to carry out a reaction on a multifunctional substrate without affecting carbonyl groups. [ 1 1. (a) Greene , TW ; Wuts , PGM Protective Groups in Organic Synthesis, , 3rd ed. ; John Wiley and Sons : New York , 1999 ; (b) Hanson , JR Protecting Groups in Organic Synthesis, , 1st ed. ; Blackwell Science, Inc : Malden , MA , 1999 ; (c) Kocienski , PJ ...