Philippe L. Durette

Umlagerungsreaktionen bei der einwirkung von trifluormethansulfonsäure auf 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-talopyranose-und 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-glucopyranose

Abstract 2,3,4-Tri- O -acetyl-1,6-anhydro-,β- D -talopyranose gave, in the presence of trifluoromethanesulfonic acid, the two talo ions 7 and 8 , which are formed in approximately equal amounts. The hydrolytic ring-opening of the two ions proceeds stereoselectively. From 7 was formed 2,3-di- O -acetyl-1,6-anhydro-β- D -talopyranose and from 8 3,4-di- O -acetyl-1,6-anhydro-β- D -talopyranose, both having an axial, acetoxyl group. The talo ion 9 can undergo ring-contraction to the 1,6-anhydrotalofuranose ion 2 . The doubly ring-contracted 1,5-anhydrotalofuranose ion 3 , which can arise from 2 and 8 , was also formed, and afforded the tri- O -acetyl derivatives of the furanose compounds 5 and 11 . The mechanism of the ring-contraction reactions is discussed. 2,3,4-Tri- O -acetyl-1,6-anhydro-β- D -glucopyranose gave preferentially with trifluoromethanesulfonic acid and antimony pentachloride the manno ion 33 , which rearranged for the most part into the altro ion 34 . The equilibrium between the manno ion 33 and the altro ion 34 is approximately 1:3.

The chemistry of maltose. Part II. Chemical modifications at the reducing unit

Chemical transformations of the reducing unit of maltose have been accomplished by routes starting from the known 1,2,2′,3′,4′,6,6′-hepta-acetate. In particular, the syntheses of 3-chloro-3-deoxy-, 3-azido-3-deoxy-, 2,3-anhydro-, 3,6-anhydro-, and 3-oxo-α-1,4-linked disaccharides are described. The 2,3-anhydride, which has the allo-configuration in the reducing ring, reacted with hydrogen bromide to give the 3-bromo-3-deoxy-maltose derivative by specific diequatorial ring opening. Methyl 4-O-(α-D-glucopyranosyl)-β-D-ribo-hex-3-ulopyranoside hexa-acetate underwent ready epimerisation to give the 2-axial epimer.