PROTECTION OF A 1,2-DIOL AS AN ACETAL.doc
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PROTECTION OF A 1,2-DIOL AS AN ACETAL ，常用化合物的合成。欢迎下载！
Protectionofa1,2-diolasanacetal;Acetonide (1,2:3,4-di-O-isopropylidene-alpha-D-galactose) SyntheticPage69(2001) Submitted16thAug2001,published17thAug2001 MelanieReich(m.t.reich@sussex.ac.uk), AcontributionfromtheCaddickGroup,Sussex ChemicalsUsed diol(D-galactose)(Avocado,1equiv.),zincchloride(Avocado, hygroscopic,storedinadesiccator(1.64equiv.)),conc.sulfuric acid(98%,7mL/mol),acetone(analar,2L/mol),sodium carbonate(Avocado(powder),3.4equiv.),water(600mL/mol), diethylether(GPR,1.5L/mol) Procedure Zincchloride(120g,0.88mol,1.64equiv.)waspartiallydissolved inacetone(1.25L)andconc.sulfuricacid(4.0mL)wasaddedat roomtemperaturetogiveaclearsolution(slightlyexothermic reaction,coolinginanice-bathmaybenecessaryonlargescale). Thediol(D-galactose)(100g,0.56mol)wasaddedinoneportion andtheresultingwhitesuspensionstirredfor6hoursatroom temperature.Asuspensionofsodiumcarbonate(200g,1.89mol, 3.4equiv.)inwater(300mL)wasaddedtotheyellowreaction mixtureat0Cinmediumsizedportions.Thesuspensionwas allowedtostirfor1/2hourbeforefiltration(discardsolid)and solventremovalinvacuo(keepwaterbathtemperaturebelow30 C,otherwisethesugarwilldecompose;Caution:theacetone- watermixtureislikelytobump).Thisgavethecrudeproductasa yellowoilbeneaththeaqueouslayer.Theorganicfractionwas separatedfromtheaqueouslayer,followedbyfurtherextraction withdiethylether(3x250ml).Theorganicsweredriedover sodiumsulfate,andthesolventremovedinvacuotoyieldthe desiredproductasapaleyellowoil(143.6g,>99%).Purificationisgenerallynotnecessary,butcanbeachievedbyflashcolumn chromatography(diethy
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