PMID: 591448Oct 1, 1977

Ring formation in a pentapeptide with alternating L and D residues: an analogy to cyclization in the biosynthesis of peptide antibiotics

The Journal of Antibiotics
M BodanszkyR L Foltz

Abstract

Acetylation of L-isoleucyl-D-alanyl-D-alanyl-L-valyl-D-leucine with acetic anhydride followed by methylation with diazomethane yielded the expected acetylpentapeptide methyl ester with molecular weight 541, but also resulted in the formation of a by-product with molecular weight 555. The incorporation of the mass corresponding to CH2 seems to be due to ring closure--via a mixed anhydride--and methylation of the cyclol derivative thus formed. A preferred, ring-like conformation stabilized by intramolecular hydrogen bonds that in turn are the consequences of the alternation of D- and L- residues in the sequence, is invoked as explanation for the unexpected cyclization. This assumption is supported by the conversion of the pentapeptide methyl ester to desthiomalformain in molten imidazole.

Related Concepts

Acetylation
Antibiotics
Cyclization
Oligopeptides
Molecular Stereochemistry

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