F. Lichtenthaler, T. Sakakibara, E. Oeser
Nov 1, 1977
Citations
0
Influential Citations
24
Citations
Journal
Carbohydrate Research
Abstract
Abstract Addition of bromine to 1,5-anhydro-tetra- O -benzoylhex-1-enitol 1 in tetrachloromethane yields 2-bromohexosyl bromide derivatives having the β- D - gluco (2) , α- D - manno (3) , and α- D - gluco configurations (4) in 6:3:1 ratios, i.e., cis -addition preponderates. Chlorination of 1 exclusively affords cis -adducts 5 and 6 , their proportion varying with the solvent (∼4:1 in toluene and ∼2:1 in tetrachloromethane). Evidence for the structure and configuration of these dihalides is presented, and the stereochemistry, at C-2 in the α- D - manno dichloride 6 is proved by X-ray crystal structure analysis. The configurations of the manno isomers 3 and 6 were determined from chiroptical properties. The β- D - gluco -dibromide 2 is hydrolyzed to the tetra- O -benzoyl-α- D -hexosulose 10 on contact with silica gel, but the α- D - manno isomer 3 requires silver nitrate-acetone for conversion into the respective β-hexosulose 11 , and the α- D - gluco -dibromide is hydrolyzed only with boiling silver perchlorate-acetone.