This paper summarizes the progress on the total syntheses of natural products accomplished in China's Mainland during the period from 2006 to 2010.The overview focuses on the first total synthesis of natural products of contemporary interest including alkaloids,cyclopeptides and cyclic depsipeptides,macrolides,terpenoids and steroids,saponins and glycosides.The development of novel synthetic strategies and methodologies,and application of new selective synthetic methods in the total syntheses of natural products are included as well.
A full account of the novel and flexible approach to hydroxylated 8-azabicyclo[3,2,1]octan-3-ones and 9-azabicyclo[3,3,1]nonan-3-ones is presented.Using keto-lactams as the starting materials,this two-step method consists of silyl enol ether formation with TBDMSOTf,lactam activation with Tf2O/DTBMP,and halide-promoted cyclization.Radical dechlorination of the resulting 1-halotropan-3-ones led to the corresponding hydroxylated tropan-3-ones,which can be hydrogenated to yield3,6-dihydroxytropanes.Starting from optically active keto-lactams,the method has been applied to the enantioselective syntheses of(+)-(1S,3S,5R,6S)-pervilleine C(6),(+)-(1S,3R,5S,6R)-valeroidine(3),(+)-(1S,3S,5R,6S)-dibenzoyloxytropane(8),and(+)-(1S,3S,5R,6S)-merredissine(9).
MAO ZhongYiHUANG SuYuGAO LongHuiWANG AiEHUANG PeiQiang
A short formal stereoselective synthesis of(-)-swainsonine(1) is described.Our synthesis started with the versatile building block(R)-3-benzyloxyglutarimide 5.Through controlled regioselective reduction,Ley's-sulfone chemistry(N-α-sulfonylation and ZnCl_2-catalyzed N-α-amidovinylation),an RCM reaction,and an amide reduction,the synthesis of unsaturated indolizidine(8R,8aS)-3 has been achieved in five steps.The indolizidine(8R,8aS)-3 is an advanced intermediate toward the synthesis of(-)-swainsonine(1).
