Altropyranosyl chloride

Tetra-O-acetyl-a-D-altropyranosyl chloride (93) reacts with antimony pentachloride to give a mixture of salts containing 54% of the v-altro derivative (94) and 39% of the v-allo derivative (95). This ratio contrasts with that observed for the equilibrium 91 92, and shows that the 1,2-O-acetoxonium ion is favored. 

In the reaction of lactose octaacetate (258) with phosphorus pentachloride and aluminum trichloride, Hudson and Kun found, in addition to the anticipated hepta-O-acetyl-lactosyl chloride, a new disaccharide derivative having the structure of the heptaacetate of 4-O-jS-D-galactopyranosyl-a-D-altropyranosyl chloride (259). The yield of 259 was raised to 35-40% when 50 grams of octa-O-acetyl-lactose (258) was heated for 20 minutes with 100 grams of aluminum... 

Octa-O-acetylcellobiose can, likewise, be rearranged by the action of corresponding excesses of aluminum trichloride and phosphorus pentachloride, and thereby gives the heptaacetate of 4-0-j3-d-glucopyranosyl-a-D-altropyranosyl chloride in 40-45% yield. Again, inversion at C-2 and C-3 of the reducing residue is observed. The formation of D-mannose and D-altrose derivatives is observed when penta-O-acetyl-D-glucopyranose is treated with aluminum trichloride-phosphorus pentachloride. ... 

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