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Carboxybenzyl (abbreviated as Cbz or Z) is a carbamate which is often used as an amine protecting group in organic synthesis.[1] It is commonly used in peptide synthesis where the carboxybenzyl protection group is introduced by reacting the amine functionality with benzyl chloroformate in the presence of a weak base:


It is used to protect amines from electrophiles. The protected amine can be deprotected by catalytic hydrogenation or treatment with HBr, yielding a terminal carbamic acid that then readily decarboxylates to yield the free amine.

The method was first used by Max Bergmann and Leonidas Zerwas in 1932 for the synthesis of peptides.[2] The abbreviation Z is in honor of Zerwas.


  1. ^ Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. pp. 248, 652–654, 1484. ISBN 978-0-19-850346-0. 
  2. ^ Max Bergmann, Leonidas Zervas (1932). "Über ein allgemeines Verfahren der Peptid-Synthese". Berichte der deutschen chemischen Gesellschaft 65 (7): 1192–1201. doi:10.1002/cber.19320650722.