Mannopyranose pentaacetate

On the other hand, if substitutions of 37 were conducted with benzoate ions, instead of acetate ions, direct Sn2 reactions occurred predominantly, and carba-y -DL-mannopyranose pentaacetate (41) was obtained. ... 

Section III, 3,a. From 133, carba-a-L-mannopyranose pentaacetate (135) was produced as follows. 

The D-mannopyranose pentaacetates were treated with stannic trichloride acetate (labeled with carbon14 in the carboxyl group) in chloroform solution, in the presence of stannic chloride. The rate at which radioactivity was introduced into the sugar acetate was followed. The exchange had been shown to be specific for the Cl-acetoxy group of the D-glucopyranose pentaacetates,33 and this was assumed in the present... 

Fig. 1.—Rates of Exchange103 of Acetate Between the D-Mannopyranose Pentaacetates (0.05 M) and SnChOAc (0.05 M) in Chloroform Solution and in the Presence of Stannic Chloride (0.05 Af).

Fig. 2.—Relative Rates of Mercaptolysis of the Pentaacetates of D-Glucopyranose and D-Mannopyranose in Ethyl Mercaptan at 0° in the Presence of Zinc Chloride 105 1, /3-D-Glucopyranose Pentaacetate 2, S-D-Mannopyranose Pentaacetate 3, a-D-Mannopyranose Pentaacetate 4, a-D-Glucopyranose Pentaacetate.

Mercaptolysis of /3-D-glucopyranose pentaacetate in ethyl mercaptan at 0°, with zinc chloride as catalyst, gives ethyl tetra-O-acetyl-l-deoxy-1-thio-/S-D-glucopyranoside in 71% yield. Under the same conditions, a-D-glucopyranose pentaacetate reacted only very slowly, but it could be shown that the deoxy-thio-/3-D-glucoside is formed in much greater amount than is the a anomer. Mercaptolysis of the D-mannopyranose pentaacetates under the same conditions for 48 hours resulted in a 70% yield of ethyl tetra-O-acetyl-l-deoxy-l-thio-a-D-mannopyranoside from the /3-D-pentaacetate, and in a 60% yield from the a anomer.103 Inspection, by preparative paper chromatography, of the residual sirups, after deacetylation, led in each case to the isolation of the anomeric ethyl-1-... 

Gomez, A M, Danelon, G O, Moreno, E, Valverde, S, Lopez, J C, A novel entry to 5a-carba-hexopyranoses from carbohydrates based on a 6-exo-dig radical cyclization synthesis of 5a-carba-beta-D-mannopyranose pentaacetate, Chem. Commun., 175-176, 1999. 

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