Of D-galactose diethyl dithioacetal

Scheme 18.—Proposed Mechanism for Photochemical Reaction of D-Galactose Diethyl Dithioacetal (44).

Treatment of D-galactose diethyl dithioacetal (112) with an aged preparation of Raney nickel or with a limited amount of the fresh reductant affords348 the corresponding 1-S-ethyl-l-thioalditol (163) as the major product the same process occurs for D-gluco, c-arabino, D-manno, and 6-deoxy-L-manno analogues, and complete reduction of 163 to the deoxyalditol 164 was accomplished by further hydrogenolysis. The stepwise conversion of a methanolic solution of 112 into 163 (isolable in 60% yield), and thence into 164 (isolable in fair... 

Micheel then slightly modified his synthesis, starting from D-galactose diethyl dithioacetal (19) (Scheme 2).33 Selective tritylation of the 6-hydroxyl group followed... 

D-Galactose was converted by ethanethiol and hydrochloric acid into crystalline D-galactose diethyl dithioacetal, which was acetonated with acetone-zinc chloride. The product (15) was reduced to the L-fu-citol derivative (16) with Raney nickel. The overall yield of 16 was 29%, and it was characterized as the crystalline 6-p-toluenesulfonate 17. Oxidation of 16 by the Pfitzner-Moffatt reagent55 proceeded readily and, after O-deacetonation, and purification of the product by chromatography on a column of silica gel, L-fucose (18 13% overall yield from D-galactose) and L-fucitol (19 1% yield) were isolated (see Scheme 3). 

A sulfur-containing, septanose form is only obtainable as a result of the protection of the C-5 and C-4 hydroxyl groups in such a way that the pyranose or furanose rings cannot be formed. 2,3,4,5-Tetra-O-acetyl-S-acetyl-6-thio-D-galactose diethyl dithioacetal (273), obtained from the corresponding 6-p-toluenesulfonate with potassium thioacet-ate, undergoes hydrolysis in the presence of mercuric chloride and... 

In the presence of catalytic amounts of p-toluenesulfonic acid, D-galactose diethyl dithioacetal (112) reacts248 with tert-butyl vinyl ether to afford the 5,6-O-ethylidene derivative 113 in 56% yield Wolfram and Parekh248 proposed that the reaction proceeds by initial, electrophilic addition of 0-6 to the double bond, followed by pro-... 

Raney nickel in aqueous ethanol normally acts to substitute hydrogen atoms in place of all of the alkyl-(or aryl- or other)thio groups present in a dithioacetal, without disturbing other substituents thus, the 2-S-ethyl-2-thio-D-pentose diethyl dithioacetal137 156, 5-S-ethyl-5-thio-D-arabinose diethyl dithioacetal145 (157), and 2,3,4,5-tetra-0-acetyl-6-S-acetyl-6-thio-D-galactose diethyl dithioacetal or its 6-thiocyanato analogue346 (158) react with Raney nickel to... 

C16H30O5S2 366.542 Some mnr data presented. Obtained as a mixture of products. (K)-4,5-Benzylidene (K)-4,5-0-Benzyli-dene-D-galactose diethyl dithioacetal [106450-95-7]... 

Asym. synthesis. A soln. of penta-O-acetyl-D-galactose diethyl dithioacetal and mercuric acetate in acetic anhydride-acetic acid (1 1) heated on a water bath until the temp, of the mixture has reached 80° a-l,2,3,4,5,6-hexa-0-acetyl-D-galactose S-ethyl monothioacetal, a single diastereomer. Y 1S%, F. e. s. E. P. Painter, Can. J. Chem. 42, 2018 (1964). 

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