Synthesis Of Chiral Glycosylated Porphyrins And Their Catalytic Asymmetric Epoxidation Of Oleifns

Porphyrins and sugars are the active substrates which exist in organisms, and theglycosylated porphyrin is a special kind of chiral porphyrins which can be used tocatalyze asymmetric synthesis reactions with high stereoselectivity using theproperties of recognition and chirality of sugar groups and the wonderful catalysisproperty of porphyrins. Moreover, the research of glycosylated porphyrins may helpto reveal the interaction mechanism of porphyrins and sugars in organisms. In thisarticle, we studied the synthesis method of glycosylated porphyrins and theasymmetric epoxidation of alkenes catalyzed by the glycosylated porphyrinssystematically. The main contents of the article were as follows:1. We obtained the porphyrins substituted with acetyl glucosyloxy group at theortho, meta and para positions of the meso-phenyl groups respectively from thenatural β-sugars. All of the substrates were characterized by UV-Vis,1H NMR andelemental analysis.2. We measured the UV-vis spectrum and fluorescence spectrum of theglycosylated porphyrins and calculated their fluorescence quantum yields. The resultsshowed that the Soret band of the porphyrins substituted with glucosyloxy group waslonger than that substituted with acetyl glucosyloxy group by5~9nm, and thefluorescence quantum yields of glycosylated porphyrins were higher than tetraphenylporphyrin expect the porphyrin substituted with acetyl glucosyloxy group at theortho-position. The maximum fluorescence emit wavelength was shorter by40~45nmand the fluorescence quantum yield was higher by20%after the derosination ofporphyrin substituted with acetyl glucosyloxy group.3. We studied the asymmetric epoxidation of alkenes catalyzed by theglycosylated porphyrins and established the oxidation system of chiral glycosylatedmetalloporphyrin-PhI(OAc)2-alkene. With the chiral manganese glycosylatedporphyrin as catalyst and PhI(OAc)2as oxidant, the highest yield of styrene reachedby98.3%with ee value of24.7%. Then we studied the influences of metals, theposition and number of substitute on the reaction. The results showed that theconversation of styrene reached12.0%,15.1%and68.9%with ee value of6.2%,6.9%,22.4%catalyzed by iron porphyrins substituted with acetyl glucosyloxy group at theortho, meta and para positions of the meso-phenyl groups respectively. And the conversation of styrene reached63.4%,68.9%and83.8%with ee value of5.4%,6.6%,23.5%catalyzed by manganese porphyrins substituted with acetyl glucosyloxy groupat the ortho, meta and para positions of the meso-phenyl groups respectively. Andwhen the metal changed from iron to manganese, the conversation of styreneincreased. And when using manganese porphyrins substituted with acetyl glucosyloxygroup at the ortho position as catalyst, the number of the substituents changed from1,2to4, the ee value of the product increased from10.5%,17.8%to23.5%. Moreover,the property of the substrate played important role in the ee value of the product.when the substrate changed from a-methyl styrene, styrene to anti-stilbene, the eevalue increased from0%,24%to52.8%. Further, the main product of the oxidation ofstyrene was S enantiomer with otho-glycosylated metalloporphyrins as catalyst,while the oxidation of styrene was R enantiomer with meta or para-glycosylatedmetalloporphyrins as catalyst.