Mild Oxidative Cleavage of 9‐BBN‐Protected Amino Acid Derivatives

Abstract Protection of the amino acid moiety using 9‐BBN is an effective method to enable side chain manipulations in synthesis of complex amino acids. We investigated the standard, mild method for deprotection of the 9‐BBN group in methanolic chloroform, and found that it relies on a slow oxidation mediated by molecular oxygen. Building on this insight, we have developed a method that allows for a fast and selective deprotection using simple peroxy acid reagents. After Fmoc protection, products were isolated in >90 % yield for a series of amino acid derivatives, including a galactosylated derivative of hydroxylysine.