Two novel steroidal 24-O-xylosides, designated as rathbuniosides R-1 (1) an
d R-2 (2), and the known amurensoside A (3) and 3-O-sulfomarthasterone (4)
have been isolated from the starfish Asterias rathbuni. The structures of a
ll the compounds were determined from their spectroscopic data, including o
ne- and two-dimensional NMR methods. The compounds I and 4 inhibit the cell
division of fertilized sea urchin eggs at doses of 7.0 x 10(-5) and 2.9 x
10(-5) M, respectively.