Methyl (2′S,3′S)-3,4-O-(2′,3′-dimethoxybutane-2′,3′-diyl)-α-L-rhamnopyranoside:: a glycosyl acceptor

The title compound, C13H24O7, is the product of the ketalization of methyl L-(+)-rhamnopyranoside with 2,3-butanedione. It crystallizes with two molecules in the asymmetric unit, which are connected by O-H center dot center dot center dot O hydrogen bonds. The C-3,4 diequatorial hydroxy groups of the methyl L-(+)-rhamnopyranoside were protected, leaving the C-2 hydroxy group free. The L-(+)-rhamnopyranoside and 2',3'-dimethoxybutane- 2',3'-diyl rings adopt chair conformations and all methoxy groups are in axial positions. The absolute configuration was assumed from the synthesis.