Arsenic-containing ribosides from the brown alga Sargassum lacerifolium: X-ray molecular structure of 2-amino-3-[5′-deoxy-5′-(dimethylarsinoyl)ribosyloxy]propane-1-sulphonic acid

Abstract

Three novel arsenic-containing ribosides, methyl 5-deoxy-5-(dimethylarsinoyl)-β-D-riboside, 1-O[5′-deoxy-5′-(dimethylarsinoyl)-β-D-ribosyl]mannitol, and a dimethylarsonio-β-D-riboside have been isolated from extracts of the brown alga Sargassum lacerifolium. In addition, five previously reported arsenic-containing ribosides, and some arsenate, were isolated from Sargassum, and dimethylarsinic acid was also shown to be present. The compounds were identified chiefly by NMR spectroscopy, and an X-ray molecular structure is reported for one of them, 2-amino-3-[5′-deoxy-5′-(dimethyl-. arsinoyl)ribosyloxy]propane-1-sulphonic acid. The stereochemistry of the aglycones in these arseniccontaining ribosides is discussed and the configuration of 3-[5′-deoxy-5′-(dimethylarsinoyl)-β-D-ribosyloxy]-2-hydroxypropane-1-sulphonic acid 4 was assigned as 2S on the basis of a comparison of NMR spectra with those of synthetic model compounds.