Glycolipids from Sponges. 10. Plaxyloside from the Marine Sponge Plakortis simplex: an Improved Strategy for NMR Structural Studies of Carbohydrate Chains

Plaxyloside, a glycolipid composed of a C35 linear polyisoprenoid alcohol aglycone and a linear carbohydrate chain made up of six â-xylopyranose units, has been isolated as its peracetate from the Caribbean sponge Plakortis simplex, and its structure determined on the basis of spectral and chemical data. Study of plaxyloside showed that: (a) carbohydrate chains with repetitive structures can be conveniently studied as their peracetates by NMR spectroscopy in C6D6, thanks to the peculiar conformational behavior of these derivatives, and (b) coupling constant analysis can be used to establish relative configurations in pyranose sugars even in the presence of conformational equilibria.