Nodulisporic acid B, B1, and B2: a series of 1′-deoxy-nodulisporic acids from Nodulisporium sp.

During the re-isolation of the lead compound nodulisporic acid A (1a) and targeted chemical screening for related compounds, we discovered a series of 1′-deoxy congeners named herein nodulisporic acids B (1b), B1 (2b), and B2 (3b). In comparison with nodulisporic acid A, these compounds were less active and were chemically unstable resulting into formation of Δ23 dehydro derivatives. Therefore, these compounds were stabilized and isolated as sodium salts and methyl ester. Nodulisporic acid B is 100-fold less active than nodulisporic acid A against fleas. The isolation, structure elucidation, and biological activities of these compounds are described.