In vitro characterization of enzymes involved in the synthesis of nonproteinogenic residue (2S,3S)-beta-methylphenylalanine in glycopeptide antibiotic mannopeptimycin.

Mannopeptimycin, a potent drug lead, has superior activity against difficult-to-treat multidrug-resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). (2S,3S)-beta-Methylphenylalanine is a residue in the cyclic hexapeptide core of mannopeptimycin, but the synthesis of this residue is far from clear. We report here on the reaction order and the stereochemical course of reaction in the formation of (2S,3S)-beta-methylphenylalanine.

Cyclopeptides with anti-inflammatory activity from seeds of Annona montana.

Four new cyclopeptides, cyclomontanins A-D (1- 4), annomuricatin C (5), and (+)-corytuberine were isolated from a methanol extract of Annona montana seeds. Their structures were elucidated by 2D NMR analysis, ESIMS/MS fragment evidence, and chemical means. The structure of 1 was confirmed by synthesis.

New cyclic peptides from the seeds of Annona squamosa L. and their anti-inflammatory activities.

Two new cyclic peptides, cyclosquamosin H ( 1) and I ( 2), together with six known cyclic peptides, squamin A ( 3), squamin B ( 4), cyclosquamosin A ( 6), cyclosquamosin D ( 7), cyclosquamosin E ( 8), and cherimolacyclopeptide B ( 9), were isolated from the seeds of Annona squamosa. All structures were confirmed by 2D nuclear magnetic resonance, chemical evidence, and electrospray ionization-mass spectromotry/mass spectrometry (ESI-MS/MS). Compound 9 was isolated from this plant for the first time.