Lactoside, ethyl

A suspension of methyl p-lactoside 13 (S.O g, 14 mmol) in benzene (130 mL) was refluxed for 17 h in the presence of BujSnO (4.18 g, 16.6 mmol) in a flask equipped with a Dean-Static separator. Then allyl bromide (20 mL) and tetrabutylammonium bromide (2 g, 6.2 mmol) were added, the solution was refluxed for 3 h, and the volatiles were evaporated. The residue was dissolved in water and washed twice with ethyl acetate. The aqueous phase was evaporated to dryness, benzene (ISO mL) and BujSnO (3.83 g) were added to the residue and the mixture was refluxed as before for 17 h. Then allyl bromide (IS mL) and tetrabutylammonium bromide (1.5 g) were added, and the solution was again refluxed for SO min. The volatiles were evaporated, and the residue was taken over in methanol. The crystalline precipitate of BrBi SnOSnBu OH), mp 80-81°C, was removed by filtration and the mother liquor was evaporated. Addition of ethyl acetate to the residue gave the allyl ether 14 as a crystalline compound (3.88 g, 70%) mp 107-112°C [a]D + 20° (c 1.0 in water). 

Trimethylsilyl)ethyl /3-lactoside (73) Acetal Benzene TBAB 80 Allyl bromide 0 3 71 0 193... 

Ethyl l-thio-/3-lactoside (79) Acetal THF Amb. r-Butyldimethylsilyl chloride 0 0 6 96 86... 

Benzyl 1-thio-lactoside and ethyl lactoside, prepared from lactose dibenzyl dithioacetal116 by the preceding methods, are necessarily pyranosides (owing to the substitution on 0-4). Stevens and coworkers310 prepared ethyl 2,3 4,5-di-0-isopropylidene-l-thio-/3-D-glucoseptanoside by partial demercaptalation of 2,3 4,5-di-O-isopropylidene-D-glucose diethyl dithioacetal. 

Ethoxypropion-2-yl)lactose (92), which was required as a model for a substrate inhibitor of viral neuraminidases, has been synthesized from benzyl 2,2, 3,3, 6,6 -hexa-0-benzoyl-P-lactoside by way of a transacetalation reaction with ethyl 2,2-diethoxypropionate. ... 

Other Alkyl and Aryl Ethers. - The reagent system of allyl ethyl carbonate and a Pd(0) catalyst, applied to carbohydrate alcohols, has been utilised for making allyl ethers under neutral conditions. The synthesis of benzyl ethers from the parent alcohols under non-basic conditions has been achieved using phenyldiazomethane and HBF4. Dibutylstannylene compounds derived from benzyl -D-lactoside and its derivatives have been regioselectively benzylated. ° Similarly, 2,2 -di-0-alkyl-4,6 4 6 -di-0-benzylidene-Qt,a-trehaloses have been prepared by regioselective alkylation of a dibutylstannylene derivative. Phase transfer catalysed benzylation... 

The 6 -deoxyanalogue of p-D-Gal-(l->4)-P-o-GlcNAc has been prepared and found to inhibit the enzymic transfer of sialic acid to the disaccharide. There has been a report on specifically deoxygenaied derivatives of 2-(trimetfaylsilyl)ethyl p-lactoside (see Vol. 26 for similar derivatives methyl lactoside). Bundle s laboratory has reported the synthesis of the 4-, 6-,... 

---