The use of boron trichloride and boron tribromide is described for the deacylation and demethylation of mono-, di-, and poly-saccharide derivatives, the last two types being converted into the monosaccharide constituents.All the monosaccharides investigated are stable to the reagent, except fructose and sorbose which are both degraded to 5-hydroxymethylfurfuraldehyde.THE oxygen atoms of ethers, esters, and inany other derivatives of carbohydrates provide sites for co-ordination with electron-deficient molecules such as Lewis acids. Since some diversity of co-ordinating power can arise in a molecule through variation in polar character and steric environment of these basic oxygen centres there are clearly possibilities for effecting particular reactions at selected sites. Some initial studies with aluminium chloride were only partially successful because this reagent is difficult to separate from the products of reaction. Boron trichloride does not have this disadvantage and has proved to be a versatile reagent in carbohydrate chemistry, as has already been reported briefly-l Although it is a gas at room temperature (b. p. 12'), boron trichloride is strongly reactive at temperatures well below its boiling point and can easily be handled in a medium such as a mixture of solid carbon dioxide and acetone (ca. --80°).2 One of its valuable uses is for removal of O-methyl groups from methylated sugars which provides a rapid and

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Phenols are not acetylated by acetic anhydride alone in carbon tetrachloride, but addition of pyridine leads to acetylation. Alcohols, in contrast, are acetylated in the absence of pyridine, but the extent of catalysis by pyridine is less than for phenols. The fact that a maximum rate of acetylation of p-chlorophenol is reached as the pyridine concentration is increased is most readily interpreted in terms of a reaction proceeding only through a hydrogenbonded form of the phenol.p-Chloro[hydroxy-2H]phenol (4 g.) was prepared by dissolving p-chlorophenol in deuterium oxide (0-5 g. ; 99.95

n-Butyraldehyde and D-glucose condensed to give 4,6-O-butylidene-~glucose , which on reduction yielded 4, B-O-butylidene-~-glucitol ( 1,3-0butylidene-L-gulitol) . Periodate oxidation of either the glucose or glucitol acetal gave 2,4-O-butylidene-~-erythrose, and thence on reduction 1,3-0butylidene-L-erythritol.THIS Paper describes the synthesis and proof of structure of 4,6-0-butylidene-~-glucitol (I) (1,3-0-butylidene-~-gulitol), an acetal which, as expected, was not obtained as an endproduct by direct butylidenation of D-glucitol.n-Butyraldehyde and D-glucose condense in the presence of a trace of concentrated sulphuric acid to yield the expected 4,6-0-butylidene-~-glucose (24-38%).This acetal appears to be dimorphic, one form melting at 150" and the other at 168"; but in chemical reactions or physical properties (infrared spectra in a Nujol mull, paper chromatography and specific rotation) other than melting point the two forms are identical. Both the dimorphs would be expected to have the same conformation as 4,6-0-benzylidene-~-glucose ,2 and from the high initial positive rotation which exhibits a downward directed mutarotation, we would infer that the solid dimorphs are both a-glucoses. The a-configuration was also tentatively assigned to them for their infrared spectra 3 in Nujol mulls. The acetal was characterised through its crystalline 9-nitrophenylhydrazone, the formation of which indicates that C-1 is not involved in the acetal linkage.The acetal consumed 2 mol. of periodate in a slightly acid solution, and liberated 2 mol. of formic acid but no formaldehyde. The major periodate oxidation product was solid 2,4-0-butylidene-~-erythrose. Evidence that the erythrose acetal was not monomeric was (a) that a Nujol mull of the compound showed no carbonyl absorption in the infrared, (b) that the acetal mutarotated in solution, and (c) that a cryoscopic determination of the molecular weight using dry benzene as solvent showed that the acetal was a dimer at infinite dilution. The material became increasingly associated with increase in concentration.Using dry acetic acid as solvent again showed that the solute was associated. Schaffer found that 2,4-0-ethylidene-~erythrose in formaniide has a molecular weight corresponding to 2-16 monomer units (no concentration of solute was stated), and he proposed that two monomer units link together through a 1,3-dioxan ring. A similar structure could exist for the butylidene acetal, for which structure (11) could presumably be a favoured conformation, since the large substituents on all three rings are equatorial.The association was rapidly reversed on dilution.

Bonner, Bourne, and Ruszkiewicz. 787160. The lodine-catalysed Conversion of Sucrose into 5-Hydroxymeth ylfurfuraldeh yde.