Book excerpt: The Fourth Edition of Greene's Protective Groups in Organic Synthesis continues to be an indispensable reference for controlling the reactivity of the most common functional groups during a synthetic sequence. This new edition incorporates the significant developments in the field since publication of the third edition in 1998, including... New protective groups such as the fluorous family and the uniquely removable 2-methoxybenzenesulfonyl group for the protection of amines New techniques for the formation and cleavage of existing protective groups, with examples to illustrate each new technique Expanded coverage of the unexpected side reactions that occur with protective groups New chart covering the selective deprotection of silyl ethers 3,100 new references from the professional literature The content is organized around the functional group to be protected, and ranges from the simplest to the most complex and highly specialized protective groups.