1.Synthesis and siderophore activity of albomycin-like peptides derived from N5-acetyl-N5-hydroxy-L-ornithine.
Dolence EK1, Lin CE, Miller MJ, Payne SM. J Med Chem. 1991 Mar;34(3):956-68.
N5-Acetyl-N5-hydroxy-L-ornithine (1), the key constituent of several microbial siderophores, has been synthesized in 23% yield overall from N-Cbz-L-glutamic acid 1-tert-butyl ester (6) derived from L-glutamic acid. Reduction of 6 to 7 and treatment with N-[(trichloroethoxy)carbonyl]-O-benzylhydroxylamine (8), and diethyl azodicarboxylate and triphenylphosphine followed by deprotection produced the protected N5-acetyl-N5-hydroxy-L-ornithine derivatives 11 and 12 in large quantities (10-20 g). Following alpha-amino and alpha-carboxyl deprotections of 11 and 12, EEDQ [2-ethoxy-N-(ethoxycarbonyl)-1,2-dihydroquinoline] mediated peptide coupling and final deprotection provided amino acid 1 and six albomycin-like peptides (20, 23, 25, 28, 35, and 36). The growth-promoting ability of each was evaluated with the siderophore biosynthesis mutant Shigella flexneri SA240 (SA 100 iucD:Tn5). These results indicate that substantial modification of the framework of peptide-based siderophores can be tolerated by microbial iron-transport systems.
2.Critical difference in chiral recognition of N-Cbz-D/L-aspartic and -glutamic acids by mono- and bis(trimethylammonio)-beta-cyclodextrins.
Rekharsky M1, Yamamura H, Kawai M, Inoue Y. J Am Chem Soc. 2001 Jun 6;123(22):5360-1.
3.Synthesis of beta- and gamma-fluorenylmethyl esters of respectively N alpha-Boc-L-aspartic acid and N alpha-Boc-L-glutamic acid.
al-Obeidi F1, Sanderson DG, Hruby VJ. Int J Pept Protein Res. 1990 Mar;35(3):215-8.
The orthogonal synthesis of N alpha-Boc-L-aspartic acid-gamma-fluorenylmethyl ester and N alpha-Boc-L-glutamic acid-delta-fluorenylmethyl ester is reported. This is a four-step synthesis that relies on the selective esterification of the side-chain carboxyl groups on N alpha-CBZ-L-aspartic acid and N alpha-CBZ-L-glutamic acid. Such selectivity is accomplished by initially protecting the alpha-carboxyl group through the formation of the corresponding 5-oxo-4-oxazolidinone ring. Following side-chain esterification, the alpha-carboxyl and alpha-amino groups are deprotected with acidolysis. Finally, the alpha-amino group is reprotected with the t-butyl-oxycarbonyl (Boc) group. Thus aspartic acid and glutamic acid have their side-chain carboxyl groups protected with the base-labile fluorenylmethyl ester (OFm) and their alpha-amino groups protected with the acid-labile Boc group. These residues, when used in conjunction with N alpha-Boc-N epsilon-Fmoc-L-lysine, are important in the formation of side-chain to side-chain cyclizations, via an amide bridge, during solid-phase peptide synthesis.
