R. Khan, K. S. Mufti
Sep 1, 1975
Citations
0
Influential Citations
44
Citations
Journal
Carbohydrate Research
Abstract
Abstract The reaction of sucrose with a combination of 2,2-dimethoxypropane, N,N -dimethylformamide, and toluene- p -sulphonic acid (reagent A ) gave, after acetylation followed by chromatography, 1′,2:4,6-di- O -isopropylidenesucrose tetra-acetate ( 1 ) in 15% yield. The structure of 1 was determined on the basis of p.m.r. and mass spectrometry, and by chemical transformations. Treatment of 1 with aqueous acetic acid afforded sucrose 3,3′,4′,6′-tetra-acetate 2. Reacetalation of 2 using reagent A gave 1 in 80% yield. The p.m.r. spectrum of 2 confirmed the presence of hydroxyl groups at C-2 and C-4. The following sequence of reactions showed that the remaining two hydroxyl groups were located at C-6 and C-1′. Selective tritylation of 2 gave 1′,6-di- O -tritylsucrose 3,3′,4′,6′-tetra-acetate ( 3 ) as the minor, and 6- O -tritylsucrose 3,3′,4′,6′-tetra-acetate ( 4 ) as the major, product. When tritylation was carried out under forcing conditions, 2 gave 3 as the major product. Acetylation of 4 afforded 6- O -tritylsucrose hepta-acetate. Mesylation of 2 gave the tetramethanesulphonate 5 , which afforded the 6-dcoxy-6-iodo derivative 6 on treatment with a refluxing solution of sodium iodide in butanone. Treatment of 3 with methanesulphonyl chloride in pyridine gave the disulphonate 7 , which on detritylation followed by acetylation gave 2,4-di- O -methanesulphonylsucrose hexa-acetate ( 9 ). Treatment of 9 with sodium benzoate in hexamethylphosphoric triamide displaced the 4-sulphonate, with inversion of configuration, to give the galacto derivative 10 .