Synthesis of Optically Active β,γ-Unsaturated α-Amino Acids and of α,β-Unsaturated γ-Amino Acids. SN2- vs. SN2’-Dichotomy of the Mitsunobu Amination of Allylic Alcohols
作者:Johann Mulzer、Günther Funk
DOI:10.1055/s-1995-3847
日期:1995.1
Novel and efficient syntheses (6-9 steps, overall yields 10-30%) are described for optically pure β,γ-unsaturated α-amino acids and α,β-unsaturated γ-amino acids, starting from (R)-isopropylidene glyceraldehyde and ethyl (S)-lactate, respectively. The key step is the Mitsunobu reaction of chiral secondary allylic alcohols with phthalimide as the nucleophile, where α,γ allylic transpositions are observed for the first time. The structure-α,γ-ratio-relationship is studied and also the stereochemistry of the allylic transposition. The α-substitution proceeds via clean SN2 inversion, whereas the γ-substitution corresponds to an (E)-anti attack of the nucleophilic with varying stereoselectivities.
Ruthenium-Catalyzed Enyne Cycloisomerizations. Effect of Allylic Silyl Ether on Regioselectivity
作者:Barry M. Trost、Jean-Philippe Surivet、F. Dean Toste
DOI:10.1021/ja046824o
日期:2004.12.1
Ruthenium catalysts effect efficiently such single-step cycloisomerization at room temperature in acetone under neutral conditions. The cycloisomerization functions with (E) or (Z) 1,2-disubstituted alkenes. Parameters influencing the enol silane geometry are discussed. The level of selectivity depends on the alkyne substitution, the geometry of the double bond, and the nature of the catalyst. Furthermore
Enantiospecific syntheses of pseudopterosin aglycones. Part 1. Synthesis of the putative aglycone of pseudopterosin G–J via an A→AB→ABC annulation strategy
作者:Robert Chow、Philip J. Kocienski、Alexander Kuhl、Jean-Yves LeBrazidec、Kenneth Muir、Paul Fish
DOI:10.1039/b102960f
日期:——
The putative aglycone of pseudopterosin GâJ and its enantiomer were synthesised enantiospecifically from 2,3-dimethoxytoluene and η3-allyl cationic complexes of molybdenum and iron respectively. The AâABâABC annulation strategy entailed the use of allyl cations or their equivalents for the creation of the three benzylic stereogenic centres. The X-ray structure of tetrahydronaphthalene (â)-41a was determined
候选的伪紫葳素 G–J 的苷元及其对映体是分别从 2,3-二甲氧基甲苯和钼及铁的 η³-烯丙阳离子复合物中以对映特异性合成的。A→AB→ABC 闭环策略涉及使用烯丙阳离子或其等效物来创建三个苯基立体中心。四氢萘 (−)-41a 的 X 射线结构已被确定。
Stereoselective Allylic Alkylations of Amino Ketones and Their Application in the Synthesis of Highly Functionalized Piperidines
作者:Cynthia Prudel、Kai Huwig、Uli Kazmaier
DOI:10.1002/chem.202000051
日期:2020.3.9
Chelated ketone enolates are excellent nucleophiles for allylic alkylations. Electron-withdrawing groups on the allyl moiety allow subsequent intramolecular Michael additions giving rise to piperidines with up to five stereogenic centers.
tetrasubstituted carboncenter; and 3) an intramolecularchirality‐transferring Michael reaction of the ketoester, with neighboring‐group participation, to introduce a chiralcenter at C15 in the target molecule. In addition, we evaluated the antimalarial activity of synthetic (+)‐(15S,16R)‐16‐hydroxy‐16,22‐dihydroapparicine and its intermediate against chloroquine‐resistant Plasmodium falciparum (K1 strain)