Unexpected Seven-Membered Ring Formation for Muraymycin-Type Nucleoside-Peptide Antibiotics

Abstract

Naturally occurring nucleoside-peptide antibiotics such as muraymycins or caprazamycins are of major interest for the development of novel antibacterial agents. However, the synthesis of new analogues of these natural products for structure–activity relationship (SAR) studies is challenging. In our synthetic efforts towards a muraymycin-derived nucleoside building block suitable for attachment to a solid support, we came across an interesting side product. This compound resulted from an undesired Fmoc deprotection with subsequent cyclization, thus furnishing a remarkable caprazamycin-like seven-membered diazepanone ring.