Glycolipids from sponges. Part 17. Clathrosides and isoclathrosides, unique glycolipids from the Caribbean sponge Agelas clathrodes

Two families of unique glycolipids, clathrosides A-C (2a-4a) and isoclathrosides A-C (5a-7a) were isolated from the Caribbean sponge Agelas clathrodes. Clathrosides and isoclathrosides are glycosides of a very-long-chain alcohol derived from fatty acids, a new class of glycolipids that appears to be characteristic of marine sponges. The six compounds differ in configuration and in the branching of alkyl chains. Stereostructures of the clathrosides were determined by NMR and CD spectroscopy, mass spectrometry, and chemical degradation. Location of the methyl branch on the proper alkyl chain required an exceptional 1-D TOCSY experiment, in which coherence was transferred through as many as 13 vicinal couplings.