Methyl (2′S,3′S)-3,4-O-(2′,3′-dimethoxy-butane- 2′,3′-di-yl) - L-rhamnopyran-oside: A glycosyl acceptor

The title compound, C13H24O7, is the product of the ketalization of methyl l-(+)-rhamnopyran-oside with 2,3-butane-dione. It crystallizes with two mol-ecules in the asymmetric unit, which are connected by O - H⋯O hydrogen bonds. The C-3,4 diequatorial hydroxy groups of the methyl l-(+)-rhamnopyran-oside were protected, leaving the C-2 hydroxy group free. The l-(+)-rhamnopyran-oside and 2′,3′-dimethoxy-butane-2′, 3′-diyl rings adopt chair conformations and all meth-oxy groups are in axial positions. The absolute configuration was assumed from the synthesis.