This paper summarizes the progress on the total syntheses riod from 2006 to 2010. The overview focuses on the first of natural products accomplished in rnainland China during the petotal synthesis of natural products of contemporary interest includ- ing 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.
The (S)-sulfide 6 has been synthesized as a synthetic equivalent of novel 3-piperidinol N-α-carbanion B via deprotonation and lithium naphthanelide (LN)-mediated reductive lithiation. The reaction of the 3-piperidinol N-α-carbanion intermediate B with carbonyl compounds gave, besides some reduced product 2a, the desired α-hydroxyalkylation products 12-17 with excellent 2,3-diastereoselectivity. The reductive α-hydroxyalkylation with unsymmetric carbonyl compounds led to only 50:50 to 77:23 diastereoselectivities at the C-1' carbinol center.
Some Stemona alkaloids belonging to the tuberostemospironine group possess a spirolactone moiety with anti-configuration （C-9/C-9a）. In this paper, we describe two approaches to this structural unity. By using bromine atom as a traceless directing group, the SmI2-mediated reductive coupling of ketone 6 and fl-bromomethacrylate proceeded with complete anti-diastereoselectivity. In the absence of an a-directing （chelation） group, the one-pot reaction of the ketone derived from alcohol 15 with the organozinc reagent generated from bromomethacrylate af- forded spiro-a-methylene-y-lactone derivative 16 as a single diastereomer. These two highly diastereoselective methods would find application in the synthesis of stemona alkaloids containing anti-configured spiro-lactone/pyr- rolidine moieties. In addition, on the basis of our previous work, the total synthesis of （-）-9-epi-11-demethyl- sessilifoliamide J （11）, and an improved synthesis of （-）-9,11-di-epi-sessilifoliamide J （9） were accomplished.
A concise five-step approach to indolizidinones 10 and 11,two advanced intermediates for the asymmetric synthesis of polyhydroxylated indolizidine alkaloids,has been developed by using N-Cbz pyrrolidin-2-yl pyridin-2-yl sulfide 13 as the chiral building block.The method features a SmI2-mediated coupling of sulfide 13 with functionalized aldehyde 14 and a tandem N-deprotection-lactamization,which constitutes a stepwise "2 + 4" annulation method for the construction of the indolizidinone ring system of 12a.
ZHENG Xiao1,2,ZHU WenFang1 & HUANG PeiQiang1 1Department of Chemistry,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China 2Key Laboratory of Synthetic Chemistry of Natural Substances
