Introduction

Abstract

In the selection of examples of well established procedures a series of decisions had to be made in order to keep the material to be presented within practical limits. These decisions resulted in a seemingly distorted picture of peptide synthesis. The number of procedures for the introduction of protecting groups appears to be excessive or at least not commensurate with the number of methods applicable for their removal. Also, relatively few methods of coupling were rendered and still less coupling reagents. These choices, however, were made not without good reasons. There is indeed a definite need for a plethora of blocking groups. The simultaneous handling of numerous side chain functions in combination with various methods of coupling and with potential side reactions related to a particular sequence of amino acids is possible only if a whole gamut of masking groups is available. For the removal of protecting groups many proposals can be found in the literature, but a closer scrutiny reveals that most of these are variations on a few themes: reduction, e.g. hydrogenolysis, acidolysis and displacement by nucleophiles. A similar repetitiveness can be discerned among coupling methods. Only exceptionally can one find methods for the formation of the peptide bond, which are not based on symmetrical or mixed anhydrides or on the aminolysis of reactive esters. Therefore, we confined ourselves mainly to the presentation of the few principal procedures.