An improved solid-phase methodology for the synthesis of putative hexa- and heptapeptide intermediates in vancomycin biosynthesis.

The biosynthesis of the vancomycin aglycone involves three oxidative phenol coupling reactions, each catalyzed by a discrete cytochrome P450-like enzyme. Studies on the mechanism and specificity of the enzyme (called OxyB) catalyzing the first coupling, require access to suitable linear peptide precursors, each conjugated as a thioester to a peptide carrier domain of the vancomycin non-ribosomal peptide synthetase. An efficient route to representative free linear peptides is described here. The method makes use of Alloc-chemistry during solid-phase assembly of the peptide backbone, but importantly and in contrast to earlier efforts, largely avoids the use of amino acid side chain protecting groups. In this way, the target linear peptides can be released directly from the solid support under very mild conditions.