Lactose anhydride

Lactosone was first prepared by the hydrochloric acid decomposition of the phenylosazone,1 although it had been noted that, in acid solutions, lactose phenylosazone forms an anhydride.197 Since its discovery,17 the benzaldehyde method has usually been employed,6-10-28 because it avoids the risks of osone hydrolysis and of alteration to the osazone. Lactosone is hydrolyzed by hot, dilute, mineral acid to D-glucosone and D-galactose.1-6 It reacts with cyanide to form an analog of iminoascorbic acid which, on acid treatment, is converted into a mixture of D-glucoascorbic acid and D-galactose.10... 

Anhydride. Since /1-lactose is less soluble than the a-isomer above 93.5°C, the crystals formed from aqueous solutions at temperatures above 93.5°C are / -lactose these are anhydrous and have a specific rotation of 35°. /1-Lactose is sweeter than a-lactose, but is not appreciably sweeter than the equilibrium mixture of a- and /1-lactose normally found in solution. 

Although Fischer described a lactose phenylosazone anhydride in 1887, little attention was paid to substances of this type until 1935 when Diels and Meyer reported the isolation of monoanhydrides of D-glucose phenylosazone, D-galactose phenylosazone, D-xylose phenylosazone, L-arabinose phenylosazone, lactose phenylosazone, and cellobiose phenylosazone, as well as a dianhydride of maltose phenylosazone, by boiling the corresponding osazones in alcoholic solution with a little sulfuric acid. Because of the apparent identity of the D-glucose phenylosazone anhydride with the 3,6-anhydro-D-glucose phenylosazone of Fischer and Zach, Diels and Meyer formulated these compounds as 3,6-anhydrides. 

Lactose phenylosazone heptaacetate yielded lactose phenylosazone anhydride hydrate,a compound previously isolated by Fischer and by Diels and Meyer. This compound also yields a pentaacetate the same structural possibilities occur here as in the case of the cellobiose phenylosazone anhydride mentioned above. 

D-Galactopyranosyl-D-arabinose was prepared from lactose oxime by dehydration with acetic anhydride and degradation of the resultant nitrile with sodium methoxide in chloroform. This galactosylarabinose has also been prepared by the oxidation of calcium lactobionate with hydrogen peroxide and a ferric salt (the Ruff degradation ). Under... 

The acetylation of lactose was examined in detail by Hudson and Johnson, with the conclusion that earlier products were mixtures of isomers. Using the acetic anhydride-sodium acetate method, they were able to obtain a 55% yield of octa-O-acetyl- -lactose which, on treatment with zinc chloride in acetic anhydride, was transformed into the a anomer. This... 

Many lactose esters, including those of long-chain fatty acids, have been prepared by using the respective acid anhydride in either alkali or pyridine, and the respective acid chloride in pyridine. A mixture of lactose and phenyl isocyanate in pyridine gives an octaphenylurethan derivative of lactose. The yellow a and anomers of lactose octakis-[p-(p-nitrophenylazo)benzoate] were prepared for chromatographic studies. ... 

The hepta-O-acetyllactosyl halides find important application in the synthesis of lactosides. Hepta-O-acetyl-a-lactosyl chloride ( a-acetochloro-lactose ) was first prepared by treatment of octa-O-acetyllactose with hydrogen chloride in acetic anhydride. Later preparations utilized, as... 

The longest known compound in this series is 1,6-anhydro-a-D-galactofuranose (261). It is relatively easily obtainable, and is usually prepared by pyrolysis of D-galactose116,294,295,792 it can also be obtained by pyrolysis of lactose, melibiose, and raffinose.196,291 An alternative route consists in the reaction of 0.2 M hydrochloric acid, or 0.1 M sulfuric acid, with D-galactose.114,115 The anhydride 261 was originally mistaken for l,3-anhydro-/3-D-galactopyranose, because of... 

Lactose forms a phenylhydrazone, osazone, and osone. The composition of these substances indicates that lactose contains one free carbonyl group. It is an anhydride of dextrose and galactose, in which one carbonyl group is involved in the union of the molecules, and one is free. The structure of the products formed on oxidizing lactose indicates that the free carbonyl group is in that part of the molecule which yields dextrose on hydrolysis. 

An easy and efficient one pot synthesis of peracetylated glycals from unprotected sugars has been described. In this method the sugar was sequentially treated with acetic anhydride and catalytic hydrobromic acid-acetic acid (to effect per-acetylation), more hydrobromic acid-acetic acid (to form the glycosyl bromide), sodium acetate (to neutralize excess hydrobromic acid) and finally a buffered mixture of sodium acetate, acetic acid, zinc-copper sulfate and water (to effect a reductive-elimination). The method was applied to the syntheses of glycals derived from D-glucose, D-galactose, L-rhamnose, L-arabinose, maltose, lactose and maltotriose. ... 

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