Two new ascochlorin derivatives, nectchlorins A (1) and B (2), together with eight known compounds (3–10), were isolated from
cultures of the leafhopper pathogen Microcera sp. BCC 17074. The structures were elucidated on the basis of NMR
spectroscopic and mass spectrometry data. The absolute configuration of 2 was determined by application of the modified
Mosher’s method. The absolute configuration of LL-Z 1272a epoxide (9), which is a plausible biosynthetic precursor of
ascochlorins, was established by chemical correlations. Cytotoxic activities of these ascochlorin derivatives were evaluated.