在很多的生物學(xué)上很重要的分子中，立體β-胺基醇結(jié)構(gòu)單元是關(guān)鍵的部分。要合成這樣的分子或其衍生物，烯烴與這兩種雜原子直接加成為最直接的方法。雖然20多年前就已經(jīng)知道的鋨或鈀參與的烯烴氨基羥基化反應(yīng)，但是為了將這一反應(yīng)發(fā)展成為催化性的不對(duì)稱(chēng)過(guò)程，仍存在一些問(wèn)題。小組最近發(fā)現(xiàn)的鋨參與的不對(duì)稱(chēng)氨基羥基化反應(yīng)（AA反應(yīng)），可以?xún)?yōu)異的對(duì)映選擇性和極好的產(chǎn)率直接將這種官能團(tuán)引入烯烴。
Sharpless不對(duì)稱(chēng)羥胺化示例：
A 20 ml of scintillation vial equipped with a magnetic stirrer wascharged with a solution of MeSO2NclNa(455mg, 3.0mmol, 3.0 equiv) in 7.5 ml ofwater, 7.5 ml of nPrOH, and (DHQD)2PHAL (40mg, 0.05mmol, 0.05 equiv). To theresulting stirred clear colorless solution was then added isopropyltrans-cinnmate (190mg, 1.0mmol), followed by K2Os2(OH)4(14.8mg, 0.04mmol, 0.04equiv). The reaction mixture turned green after several minutes and was stirredfor 3.5 hours, by which time the reaction mixture has turned a clear, lightyellow. The presumed significance of the color change as an indication of theend point of the reaction was confirmed by a TLC analysis, which revealed thatno olefin remained. (With dimethyl fumarate the green color was only observedwhen an additional 0.5 equiv tert-butyl hypochlorite was added. For thefumarate case, the extra tert-butyl hypochlorite also resulted in much betteree and yield.) the reaction was then quenched by addition of 10 ml of saturatedNa2S3( This reductive quench is exothermic and cooling is needed forlarge-scales). The added salt caused phase separation. The aqueous phase wasseparated and extracted with ethyl acetate(3X30ml). The combined organic phaseswere dried over Mg2SO4 and concentrated to afford the crude product(impuritieswere mainly methanesulfonamide and diol). For an accurate yield the crudeproduct was purified by flash chromatography( SiO2, 30% ethyl acetate/hexane)and afforded 195mg(65%, >99%ee) crystalline aminohydroxylation product.
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相關(guān)反應(yīng)介紹
在鋨催化下胺基和羥基對(duì)烯烴進(jìn)行順式加成，通過(guò)加入手性配體（二氫奎寧或二氫奎寧衍生物類(lèi)手性配體）實(shí)現(xiàn)對(duì)映選擇性。
