| Abstract
| - A series of novel antibiotics with activity against methicillin-resistant staphylococci and vancomycin-resistant enterococci has been purified, and their structures have been characterized using spectroscopicanalyses and chemical conversions. These antibiotics, designated mannopeptimycins α−ε (1−5), areglycosylated cyclic hexapeptides containing two stereoisomers of an unprecedented amino acid, α-amino-β-[4‘-(2‘-iminoimidazolidinyl)]-β-hydroxypropionic acid (Aiha), as a distinguishing feature. The cyclic peptidecore of these antibiotics is attached to a mannosyl monosaccharide moiety in 2 and to mannosylmonosaccharide and disaccharide moieties in 1, 3, 4, and 5. The presence and position of an isovalerylgroup in the terminal mannose (Man-B) in 3−5 are critical for retaining antibacterial potency.
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