Five norisoprenoids were isolated from the green marine alga Ulva lactuca. Two new compounds were assigned to (3R,5R,6R,7E)3,5,6-trihydroxy-7-megastigmen-9-one (1) and (3S,5R,6S,7E)3,5,6-trihydroxy-7-megastigmen-9-one (2). The structures and absolute configurations of the five compounds were determined by analyses of NMR, MS and circular dichroism (CD).
A new triterpene glycoside, rollentoside A, has been isolated from Asterias rollentoni Bell and identified as 3beta-O-{3-O-methyl-beta-D-xylopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-quinopyranosyl-(1-->2)-O-beta-D-xylopyranosyl}-16-beta-acetoxy-23S-acetoxy-holost-7-ene (1), together with a new natural product, rollentoside B (2). The structures of compounds1 and 2 were elucidated by extensive 1D and 2D NMR investigation (1H-1H COSY, TOCSY, HSQC, HMBC, NOESY).
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