METHYLATION OF SUGAR DITHIOACETALS: V. D-MANNOSE DIETHYL DITHIOACETAL

Partial methylation of D-mannose diethyl dithioacetal in tetrahydrofuran with methyl iodide and silver oxide yielded 2-, 3-, and 6-O-methyl-D-mannose in the ratio of 12:1:1, respectively. The major component, 2-O-methyl-D-mannose, was characterized as the phenyl-hydrazone and the other isomers identified by electrophoresis. The Mg values of these mono-O-methyl ethers were recorded.

THE p-BROMOPHENYLOSAZONES OF 3- AND 5-O-METHYL-D-XYLOSE AND AN APPLICATION OF THIN-LAYER CHROMATOGRAPHY

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METHYLATION OF SUGAR DITHIOACETALS: IV.D-XYLOSE DIETHYL DITHIOACETAL

Partial methylation of D-xylose diethyl dithioacetal in tetrahydrofuran with methyl iodide and silver oxide yielded 2-, 3-, and 5-O-methyl-D-xyloses in the ratio of 20:10:1. The poly-O-methylated components were not examined. The 2-O-methyl-D-xylose was identified as the crystalline sugar and the 3-O-methyl ether as the phenylosazone and p-bromophenylosazone. An alternative preparation of the dithioacetal in tetrahydrofuran solution is described.

METHYLATION OF SUGAR DITHIOACETALS: III. D-GALACTOSE DIETHYL DITHIOACETAL

Partial methylation of D-galactose diethyl dithioacetal in tetrahydrofuran with Purdie's reagents yielded 2-, 3-, and 6-O-methyl-D-galactoses in approximately equal amounts. Poly-O-methyl-D-galactoses were not investigated. These three mono-O-methyl ethers were identified as crystalline 2-O-methyl-D-galactose, 3-O-methyl-D-galactose phenylosazone, and 6-O-methyl-D-galactose phenylhydrazone. Paper çhromatographic separation of all monomethyl-D-galactopyranoses was achieved by addition of borax to the irrigating solvent.

METHYLATION OF SUGAR MERCAPTALS: II. L-ARABINOSE DIETHYL MERCAPTAL

Methylation of L-arabinose diethyl mercaptal in tetrahydrofuran with methyl iodide and silver oxide yielded mainly 2-O-methyl-L-arabinose and a trace of 5-O-methyl-L-arabinose. The identity of the major component was inferred by its behavior on electrophoresis and confirmed by the preparation of the crystalline amide. The polymethylated components were not examined. 2-O-Methyl-L-arabono-γ-lactone, previously known as a sirup, has now been obtained crystalline.

THE SYNTHESIS OF 5-O-METHYL-L-ARABINOSE

5-O-Methyl-L-arabinose is thought to occur in the hydrolysis products of methylated wheat bran hemicellulose. This sugar has now been synthesized from ethyl 2,3-di-O-acetyl-5-O-trityl-α-L-arabinoside by detritylation, methylation, and hydrolysis. The free sugar was obtained as a sirup and was characterized by periodate oxidation together with the preparation of a crystalline osazone and a crystalline lactone.