New 3-Hydroxyquinaldic Acid Derivatives from Cultures of the Marine Derived Actinomycete M-157.

Fractionation of the bioactive extract of a culture of the marine derived actinomycete M-157 led to the isolation of the known 3-hydroxyquinaldic acid (), its amide () and three new derivatives (⁻) containing different amino acid residues. The structures of the new molecules (⁻), including their absolute configuration, were determined by the analysis of their ESI-TOF MS and one-dimensional (1D) and two-dimensional (2D) NMR spectra and advanced Marfey's analysis of their hydrolyzation products. Compound spontaneously dimerized in solution to give the disulfide derivative .