An enantioselective version of the AB+B→ABCD-type steroid total synthesis
摘要:
Diene 1 and dienophile 4a in a Diels/Alder reaction mediated by a chiral ligand-modified Lewis acid enantioselectively furnish adduct 5a (chem. yield. 64%, e.e.: 73%), which after partial deoxygenation and final enantioselection by recrystallization affords 5b. The latter compound can easily be converted via Torgov's pentaenone 6a into estrogens or progestogens.
Enantioselective Synthesis of (+)-Estrone Exploiting a Hydrogen Bond-Promoted Diels−Alder Reaction
作者:Marko Weimar、Gerd Dürner、Jan W. Bats、Michael W. Göbel
DOI:10.1021/jo100053j
日期:2010.4.16
Starting from Dane’s diene and methylcyclopentenedione, (+)-estrone is synthesized along the Quinkert−Dane route in 24% total yield. The keystep is an enantioselective Diels−Alderreaction promoted by an amidiniumcatalyst as efficiently as by a traditional Ti-TADDOLate Lewis acid.
从 Dane 的二烯和甲基环戊烯二酮开始,沿 Quinkert-Dane 路线合成 (+)-雌酮,总产率为 24%。关键步骤是由脒催化剂与传统的 Ti-TADDOLate Lewis 酸一样有效地促进对映选择性 Diels-Alder 反应。
Organocatalytic Asymmetric Formation of Steroids
作者:Kim Søholm Halskov、Bjarke S. Donslund、Sebastian Barfüsser、Karl Anker Jørgensen
DOI:10.1002/anie.201400203
日期:2014.4.14
variety of substituents in the A ring in high yields and up to greater than 99 % ee. The reaction has been extended to include the construction of B‐ and D‐homosteroids as well as steroids containing heteroatoms in the B ring. The angular substituent at C13 can be varied and alkyl, ester, and sulfone functionalities are introduced with excellent stereoselectivities. Simple synthetic procedures provide access
A C2-Chiral Bis(amidinium) Catalyst for a Diels−Alder Reaction Constituting the Key Step of the Quinkert−Dane Estrone Synthesis
作者:Svetlana B. Tsogoeva、Gerd Dürner、Michael Bolte、Michael W. Göbel
DOI:10.1002/ejoc.200200635
日期:2003.5
A novel C2-chiralbis(amidinium) salt 12 has been synthesised from 5-(tert-butyl)isophthalic acid. The hydrogen-bond-mediated association of dienophiles 3a and 3b with the chiral host molecule 12 accelerates the Diels−Alderreactions with diene 2 by more than three orders of magnitude. In addition, enantioselective formation of the desired adducts is observed under catalysis with 12. Good ratios of
Reduction of conformational space by 1,2-diketone·Lewis acid chelates
作者:Gerhard Quinkert、Heinrich Becker、Michael Del Grosso、Gernot Dambacher、Jan W. Bats、Gerd Dürner
DOI:10.1016/s0040-4039(00)91821-5
日期:1993.10
Various 1,2-diketones function as chelating ligands with Ti and Sn, but not with Al
Axially Chiral Amidinium Ions as Inducers of Enantioselectivity in Diels−Alder Reactions
作者:Tilmann Schuster、Markus Bauch、Gerd Dürner、Michael W. Göbel
DOI:10.1021/ol991276i
日期:2000.1.1
Enantioselective catalysis of Diels-Alder reactions is mostly achieved by coordinating the dienophile to relatively strong chiral Lewis acids. Here we report on a novel approach employing the hydrogen bond mediated association of dienophiles to chiral host molecules, In a reaction forming the steroid skeleton of norgestrel, chiral amidinium ions induce 5:ent-5 ratios of up to 2,5:1. Improved and simplified amidinium catalysts may become interesting candidates to perform stereoselective transformations.