Lajollamycins, Nitro Group-Bearing Spiro-β-lactone-γ-lactams Obtained from a Marine-Derived Streptomyces sp.

Lajollamycins (1-4), each of which bears a spiro-beta-lactone-gamma-lactam ring and a nitro-tetraene moiety, were obtained from a marine-derived Streptomyces strain isolated from the southern area of Jeju Island, Republic of Korea. The planar structures of the lajollamycins were elucidated on the basis of spectroscopic analyses by NMR, UV, IR, and MS. The absolute configuration of lajollamycin (1), the planar structure of which has been previously reported, was determined using J-based configuration analysis based on H-1-H-1 and H-1-C-13 coupling constants, as well as ROESY correlations, followed by the modified Mosher's method. The absolute configurations of lajollamycins B-D (2-4) were established by comparing their CD spectra with that of 1. The lajollamycins exhibited moderate inhibitory activity toward Candida albicans isocitrate lyase.