Formation of beta-lactose from alpha- and beta-lactose octaacetates, and from alpha-lactose monohydrate
1979
Parrish, F.W. | Ross, K.D. | Simpson, T.D.
Deacetylation of alpha - and beta -lactose octaacetates with 14 mM potassium methoxide in methanol for 24 h at 25 deg C produced crystalline beta -lactose at 97% yield; with alpha -lactose octaacetate and a reaction time of only 40 min, amorphous alpha -lactose predominated (3:1, alpha : beta ). Reaction of alpha - or beta -lactose octaacetate with potassium methoxide in methanol at reflux gave a white precipitate after a few min, and the products isolated in 70-72% yield after 3 h, was crystalline lactose. Deacetylation of alpha - and beta -lactose octaacetate with 0.28 M triethylamine in methanol for 17 h at 25 deg C gave in each instance a mixture of anhydrous alpha - and beta -lactose (87% yield) in the ratio 55:45; this mixture was converted into crystalline beta -lactose when boiled under reflux with potassium methoxide in methanol. Treatment of alpha - or beta -lactose octaacetate with 16% methanolic NH3 gave an anhydrous lactose product, mainly amorphous, but containing approx. 20% of crystalline material having a m.p. of 216 deg C, identical to that of alpha -lactose; the anomeric ratio of alpha : beta was 55:45. Effects of the deacetylation reagents and conditions on the various forms of lactose, e.g. alpha -lactose monohydrate, 3 anhydrous forms of alpha -lactose, were also studied.
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