A solubilizing polar protecting group for peptide syntheses, viz. 4‐sulfobenzyl, combines the advantages of the solubilizing sulfo‐ and the protecting benzyl function. The new protecting group is introduced by means of sodium 4‐(bromomethyl)benzenesulfonate (1) into salts of N‐protected amino acids and peptides.
Eine löslichkeitsvermittelnde, polare Schutzgruppe für Peptidsynthesen, 4‐Sulfobenzyl, vereinigt die Vorzüge der solubilisierenden Sulfo‐ und der schützenden Benzylfunktion. Die neue Schutzgruppe wird mit dem im 100g‐Maßstab zugänglichen Natrium‐4‐(brommethyl)benzolsulfonat (1) in Salze N‐geschützter Aminosäuren und Peptide eingeführt.
The preparation of the 4‐sulfobenzyl esters of 18 amino acid derivatives is described. This carboxyl protecting group was introduced according to Hubbuch et al. (1980). The caesium or dicyclohexylammonium salts of N‐terminal protected amino acids were reacted with 4‐(bromomethyl)benzenesulfonate (1). After N‐terminal deblocking, the amino acid‐4‐sulfobenzyl esters were isolated as zwitterions. The protecting group was removable by catalytic hydrogenation and by saponification. The 4‐sulfobenzyl esters could be easily converted to amides and hydrazides. They were stable to 2 M hydrogen bromide in acetic acid as well as to a 10‐fold excess of trifluoromethane sulfonic acid in trifluoro‐acetic acid. The behaviours of +H2‐Gly‐Phe‐Leu‐OBzl‐SO‐3 and the corresponding methyl, benzyl and 4‐nitrobenzyl esters were compared under various conditions.
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