Cyclic Ketals of Tartaric Acid: Simple and Tunable Reagents for the Determination of the Absolute Configuration of Primary Amines
摘要:
2,2-Diphenyl-[1,3]dioxolane-4,5-dicarboxylic acid (DPD) and 2,2-dinaphthalen-2-yl-[1,3]dioxolane-4,5-dicarboxylic acid (DND) have been synthesized starting from dimethyl tartrate. DPD and DND amides of alpha-chiral primary amines showed significantly different H-1 chemical shift values depending on the stereochemistry of the derivatizing agent. On the basis of this chemical shift difference, the absolute configuration of amine substrates could be assigned. DND amides showed significantly larger chemical shift differences than the corresponding DPD amides allowing for a more error-free assignment.
Enantioselective Photocycloaddition Mediated by Chiral Brønsted Acids: Asymmetric Synthesis of the Rocaglamides
作者:Baudouin Gerard、Sheharbano Sangji、Daniel J. O'Leary、John A. Porco
DOI:10.1021/ja062621j
日期:2006.6.1
Enantioselective syntheses of methyl rocaglate and the related natural products rocaglamide and rocaglaol are outlined. The approach involves enantioselective [3 + 2] photocycloaddition promoted by chiral Brønsted acids (TADDOLs) to afford an aglain precursor followed by a ketol shift/reduction sequence to the rocaglate core.
Seebach, Dieter; Beck, Albert K.; Dahinden, Robert, Croatica Chemica Acta, 1996, vol. 69, # 2, p. 459 - 484
作者:Seebach, Dieter、Beck, Albert K.、Dahinden, Robert、Hoffmann, Matthias、Kuehnle, Florian N. M.
DOI:——
日期:——
On the origin of changes in topicity observed in Diels–Alder reactions catalyzed by Ti–TADDOLates
作者:Belén Altava、M.Isabel Burguete、Eduardo Garcı́a-Verdugo、Santiago V. Luis、Juan F. Miravet、Marı́a J. Vicent
DOI:10.1016/s0957-4166(00)00464-x
日期:2000.12
New C-2 symmetric TADDOLs containing different groups at the 2-position of the dioxolane ring have been prepared. The Ti catalysts derived from these have been studied in the Diels-Alder reaction of cyclopentadiene and (E)-2-butenoyl-1,3-oxazolidin-2-one. Substituents at the C-2 position of the dioxolane ring can play an important role in determining the selectivity as well as the nature of the major isomer. This effect is more important for TADDOLs containing bulky aromatic groups such as 3,5-dimethylphenyl- or 1-naphthyl at the alpha -positions. Experimental evidence supports the hypothesis that pi-pi. interactions between aromatic groups at the C-2 and the ones at the a-positions are critical in this respect. (C) 2001 Elsevier Science Ltd. All rights reserved.
TADDOL-TiCl2 catalyzed Diels-Alder reactions: unexpected influence of the substituents in the 2-position of the dioxolane ring on the stereoselectivity
作者:Belén Altava、Ma Isabel Burguete、JoséM. Fraile、JoséI. García、Santiago V. Luis、JoséA. Mayoral、Ana J. Royo、María J. Vicent
DOI:10.1016/s0957-4166(97)00264-4
日期:1997.8
Several alpha,alpha,alpha',alpha'-tetra(3,5-dimethylphenyl)-1,3-dioxolane-4,5-demethanols have been synthesized, and their TiCl2 derivatives used as catalysts in the reaction of cyclopentadiene with (E)-2-butenoyl-1,3-oxazolidin-2-one. The substituents in the 2-position of the dioxolane ring exert a decisive influence on the extent and direction of the asymmetric induction and, consequently any possible enantiomer of the cycloadducts can be preferentially obtained by changing these substituents. Molecular mechanics calculations of the structures and relative energies of the possible dienophile-catalyst complexes offer a tentative explanation for the results described. (C) 1997 Elsevier Science Ltd.
Highly Enantioselective Protonation of the 3,4-Dihydro-2- methylnaphthalen-1(2H)-one Li-Enolate by TADDOLs
作者:Ana Cuenca、Mercedes Medio-Simón、Gregorio Asensio Aguilar、Daniel Weibel、Albert K. Beck、Dieter Seebach