No abstract

Seed germination of Melampyrum lineare proceeds only after activation followed by an extended period of chilling. Up to one-third of seeds can be activated by storage at room temperature, while all seeds are activated if treated with gibberellic acid. Chilling before activation is ineffective.

The dimethyl thioacetals of D-glucoSe and D-mannose have been condensed with acetone. Mannose dimethyl thioacetal forms a crystalline 3,4:5,6-di-0-isopropylidene derivative while glucose forms a mixture of the crystalline 3,4:5,6-di-0-isopropylidene and syrupy 2,3: 5,6-di-0-isopropylidene isomers. These three di-0-isopropylidene dimethyl thioacetals have been converted via crystalline intermediates into the corresponding di-0-isopropylidene dimethyl acetals. These derivatives are suitable open-chain co~npounds for use in IcoenigsKnorr syntheses and provide ( a ) mannose with the Cp hydroxyl free, (b) glucose with the C2 hydroxyl free, and (c) glucose with the C1 hydroxyl free.

4-0-8-D-Galactosyl-D-glucose (lactose) has been synthesized using a modification of the Koenigs-Icnorr reaction. INTRODUCTION4-O-~-~-Galactosyl-D-glucose (lactose) occurs in all mammalian milk to the extent of about 5Yv. I t has also been reported in the long-styled pollen of forsythia flowers. I t was prepared in 1942 by Haskins, Hann, and Hudson (1) from epilactose (4-0-0-Dgalactosyl-D-mannose), but has not previously been synthesized directly.One of the most useful methods of disaccharide synthesis is that due to Koenigs and Knorr (2). They prepared tetra-0-acetyl-a-D-glucopyranosyl-bromide and found that this, in the presence of silver carbonate or dry pyridine, reacted with methanol to form methyl-0-D-glucopyranoside. The reaction-essentially the elimination of hydrogen halide between a glycosyl halide and a hydroxyl group-was adapted for disaccharide synthesis by Helferich (3) and by Hudson (4). They allowed the acetobrom sugar to react with a suitably substituted sugar derivative in a dry inert medium in the presence of silver carbonate or silver oxide. With modern refinements-use of "Drierite" as drying agent and small amounts of iodine as catalyst-good yields can be obtained in the case of 1 -+ 6 linked hexose disaccharides, where a primary hydroxyl group is involved. However, up to the present only small yields have been obtained in the case of disaccharides where a secondary hydroxyl group is involved. This is due to the lesser reactivity of the secondary hydroxyl group and to steric hindrance by the alcohol component due to the presence of the hemiacetal ring and the substituent groups. I t was thought that this second factor might be lessened-and thus greater yields obtained-by the use of an open-chain sugar derivative as the alcohol reactant. Here the accessibility of the hydroxyl group is much greater than in the corresponding ring compound.In the present work 2,3-5,6-di-0-isopropylidene-D-glucose diethyl acetal was condensed with acetobrom-D-galactose under standard Koenigs-Knorr conditions (5). The reaction mixture was boiled with sodium hydroxide solution to remove acetyl groups from the product and to destroy excess acetobrom-galactose, cooled, and deionized. Hydrolysis of isopropylidene and acetal groups was carried out with hot dilute acetic acid. The resulting mixture of mono-and di-saccharides was separated by charcoal-and paperchromatography. Lactose was obtained crystalline in 3.57, yield, which is well in excess of the yields usually obtained from Koenigs-Knorr syntheses where a secondary hydroxyl group is involved. Two other disaccharide fractions were obtained in small yield. These have not been completely identified but presumably result from isomers of 2,3-5,6-di-0-isopropylidene-D-glucose diethyl acetal. These are inevitably present in small amount as a result of the method of preparation of this compound (via a mercaptal mixture (8) consisting mainly of the 2,3-5,6-di-0-isopropylidene derivative). EXPERIMENTALOptical rotations were measured in water a t 2 1°f 2' C. The fo...

The disaccharide named in the title, 6-0-8-D-galactopyranosyl-D-galactose, and the a(?)-substituted isomer have been synthesized in low yield by the condensation of acetobromo-Dgalactose and di-0-isopropylidene-aldehydo-D-galactose dimethyl acetal.