N-Hydroxy Amides. II. N-Benzyloxy α-Amino Acid N-Hydroxysuccinimide Esters and Synthesis of a Hexapeptide Having an Alternating N-Hydroxy Amide–Amide Sequence

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Abstract
Acylation of a series of N-benzyloxy α-amino acid derivatives with N,N-phthaloyloglycine shows that the yield decreases with increasing bulkiness of the substituent even by the acyl chloride or mixed anhydride procedure, and that the use of an excess reagent or a double acylation technique is needed to attain a good yield. The low reactivity of the benzyloxyamino group enables us to utilize N-benzyloxy α-amino acid N-hydroxysuccinimide esters without N-protection in the acylation of the usual amino group. In an attempt to lengthen the chain of an N-hydroxy peptide, a hexapeptide anilide having an N-hydroxy-Dl-alanylglycyl sequence was synthesized via N-benzyloxy peptides. The complex forming tendency of the hexapeptide with iron(III) is examined.