LC-MS-Guided Isolation of Cyanogripeptides A–C, Cyclolipopeptides with β-Methyl-Leucine Residues, from an Actinoalloteichus cyanogriseus LHW52806

Cyanogripeptides A–C (1–3), three new cyclolipopeptides with unusual β-methyl-leucine residues, were identified from an Actinoalloteichus cyanogriseus LHW52806 using an LC-MS-guided strategy. The structures of compounds 1–3 were elucidated by 1D/2D NMR, HR-MS/MS, and the advanced Marfey's method. The absolute configuration of the β-methyl-leucine residue was determined by a combination of stereoselective biosynthesis of (2S,3R)-β-methyl-leucine, racemization to its epimer (2R,3R)-β-methyl-leucine, and the advanced Marfey's method. The biosynthetic pathway of cyanogripeptides was deduced by analyzing the genome of A. cyanogriseus LHW52806. Compound 3 exhibited antibacterial activity against Helicobacter pylori G27, Helicobacter pylori 26695, and Mycolicibacterium smegmatis ATCC607 with MIC values of 32 μg/mL.