New 4α-methyl steroids from a Chinese soft coral Nephthea sp.

Three new 4α-methyl steroids, 4α-methyl-ergost-7,24(28)-diene-3β-ol-23-one (1), 4α-methyl-ergost-8(14),24(28)-diene-3β-ol-23-one (2), 4α-methyl-ergost-24(28)-en-3β,11β-diol-23-one (3), and two new polyoxygenated steroids, ergost-5,25-diene-3β,24S,28-triol (4), ergost-5,24(28)-diene-3β,23S-diol (5), along with one known steroid 24-methylencholesterol (6) were isolated from the soft coral Nephthea sp. Their structures including the relative configurations were elucidated by extensive 1D and 2D NMR spectra analysis. The absolute configurations of (4) and (5) were determined by the Mosher's method.