Studies of triorganotin-pentofuranoses
A series of novel triphenylstannyl-C, (triphenylstannyl)methyl- O- and (tributylstannyl)methyl-O- substituted pentofuranose compounds have been synthesised. Two methods were employed: (i) the reaction of triphenyltinlithium with derivatised and protected (or partially protected) carbohydrates, and (ii) the reactions of carbohydrate alkoxides with (iodomethyl)triphenyltin and (iodomethyl)tributylin. The solution structures of the triorganotin-carbohydrate compounds were investigated by 1H, 13C and 119Sn NMR spectroscopy. In solution all of the triorganotin-carbohydrates were shown to contain four-co-ordinate tin atoms. The solid-state structures were investigated by a combination of solid-state NMR spectroscopy and single-crystal X-ray diffraction. There were no major conformational changes between the two phases for any of the compounds. The molecular structures of methyl 5-deoxy-2,3- O-isopropylidine-5-triphenylstannyl-beta-D-ribofuranoside and 5-deoxy-1,1- O-isopropylidine-5-triphenylstannyl-alpha-D-xylofuranose were determined. Two different molecular conformations were identified for the former compound, and hydrogen-bonding between adjacent molecules was shown to be present in the latter case. The reactions of the triorganotin-carbohydrate compounds with iodine and bromine were studied. The results indicated that the rate of cleavage of butyl-tin bonds was much slower than the cleavage of phenyl-tin bonds. The reactivity of the tin-phenyl bond was found to depend greatly on the structure of the carbohydrate ligand. Evidence of increased co-ordination in solution was found for the mono-halo derivatives of methyl 5-deoxy-2,3-O-isopropylidine-5-triphenylstannyl-beta-D-ribofuranoside and 5-deoxy-1,2-O-isopropylidine-5-triphenylstannyl-alpha-D-xylofuranose. The molecular structures of 5-deoxy-5-iododiphenylstannyl-1,2-O-isopropylidine-alpha-D-xylofuranose and 5-deoxy-5-diiododiphenylstannyl-1,2-O-isopropylidene-alpha-D-xylofuranose were determined. In the solid-state the geometry about the tin atoms was found to be distorted trigonal bipyramidal.