The ‘lactone method’: enantioselective preparation of novel P,N-biaryl ligands and their use in the synthesis of the biarylic alkaloids, ancistrotanzanine B and ancistroealaine A

Bringmann, Gerhard; Pfeifer, Robert‐Michael; Schreiber, Petra; Hartner, Kristina; Schraut, Michaela; Breuning, Matthias

doi:10.1016/j.tet.2003.12.070

Cited by 26 publications

(27 citation statements)

References 54 publications

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“…The energy required to reach a transition state in such a step, where a biphenyl becomes essentially planar, depends on the torsion angle of the biphenyl in its local energy minimum in similarity to the Hammond postulate. This was demonstrated previously by Bringmann and co-workers. , For instance, biaryls with short banisters (sB, Figure ) have smaller torsion angles and display lower enantiomerization barriers because their geometry resembles the transition-state structure better than those with longer banisters (lB, Figure ). Therefore, one could expect a correlation between the activation energy and the C–Y bond length.…”

Section: Discussionmentioning

confidence: 98%

Sulfone “Geländer” Helices: Revealing Unexpected Parameters Controlling the Enantiomerization Process

et al. 2021

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The two sulfonyl-bridged Geländer helices 1a and 2a are obtained by oxidation of the corresponding sulfide bridged precursors 1b and 2b. Both Geländer structures are fully characterized by NMR, high-resolution mass spectrometry, and optical spectroscopies. X-ray diffraction with a single crystal of 2a provides its solid-state structure. Both Geländer helices 1a and 2a are separated into enantiomers, and their racemizations are monitored by circular dichroism. For 1a, consisting of two equally sized macrocycles, a substantial increase in the enantiomerization barrier is observed upon going from the sulfide to the sulfone, and only a subtle rise is detected for the constitutional isomer 2a with two macrocycles of different size during the same transformation. This results not only in 1a with the highest configurational stability in the series of hitherto investigated Geländer structures but also challenges the so far hypothesized correlations between bridging structures and the Gibbs free energy of enantiomerization. The simulation of the enantiomerization process in the macrocyclic subunits suggests the proximity of the endotopic hydrogens as parameter responsible for the heights of the enantiomerization barrier.

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Section: Discussionmentioning

confidence: 98%

Sulfone “Geländer” Helices: Revealing Unexpected Parameters Controlling the Enantiomerization Process

et al. 2021

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“…Enantiomerically pure atropisomers commonly employed as chiral ligands are generally made by resolution: there are still relatively few effective methods for direct asymmetric coupling to form single enantiomers 3. Kinetic resolution4 and dynamic resolution5 under kinetic5a or thermodynamic5b control are particularly appealing given the possibility offered by atropisomerism for thermal racemization of the less reactive enantiomer. The use of desymmetrization for the synthesis of single atropisomers is rare 6.…”

Section: Methodsmentioning

confidence: 99%

Biocatalytic Desymmetrization of an Atropisomer with both an Enantioselective Oxidase and Ketoreductases

Yuan¹,

Page²,

Worrall³

et al. 2010

Angewandte Chemie

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Atropisomeric ligands have found numerous powerful applications in catalysis, [1] and the atropisomeric biaryl bisphosphine binap played an important role in the award of a Nobel Prize to Noyori in 2001.[2] Enantiomerically pure atropisomers commonly employed as chiral ligands are generally made by resolution: there are still relatively few effective methods for direct asymmetric coupling to form single enantiomers. [3] Kinetic resolution [4] and dynamic resolution [5] under kinetic [5a] or thermodynamic [5b] control are particularly appealing given the possibility offered by atropisomerism for thermal racemization of the less reactive enantiomer. The use of desymmetrization for the synthesis of single atropisomers is rare. [6] Following the early example of enantioselective lithiation reported by Raston and co-workers, [6b] the research groups of Hayashi [6c] and Harada [6d] also reported chemical methods for desymmetrizing biphenyl compounds. A single example of the enzymatic desymmetrization of a biaryl compound with a lipase was reported by Matsumoto et al.[6e]Herein, we report two novel and complementary biocatalytic approaches to the enantioselective synthesis of atropisomers by the desymmetrization of appropriate achiral substrates containing a pair of enantiotopic functional groups. The atropisomer in question is the diaryl ether 2, which may be formed either by enantioselective oxidation of the symmetrical diol 1 or by the corresponding reduction of the symmetrical dialdehyde 3 (Scheme 1). The enzymes we employed for these transformations were 1) a variant of galactose oxidase (GOase) which had been previously evolved to accept chiral benzylic alcohols as substrates with high enantioselectivity (1!2) [7] and 2) a family of ketoreductases that are known to possess good activity and enantioselectivity for the asymmetric reduction of benzylic ketones (3!2). [8] Atropisomeric diaryl ethers [9] form part of the structure of vancomycin [10] and are promising scaffolds for the construction for new chiral ligands.[11] Dialdehyde 3 and diol 1 were made by our published route. [9] In an initial screen, we attempted enantioselective acetylation by incubating diol 1 with Candida antarctica lipase B and vinyl acetate. Slow acylation of 1 was observed with approximately 50 % conversion after 24 h to the monoacetate 4 and modest enantioselectivity (60 % ee). In contrast, when diol 1 was incubated with the previously reported M 3-5 variant of GOase, [7] rapid oxidation to the monoaldehyde (P)-2 resulted in 80 % conversion after 24 h to material with 94 % ee.During the oxidation of 1 to 2, rapid formation of the product (P)-2 with approximately 88 % ee (see below for assignment of the absolute configuration) was observed after 1 h, followed by a slower increase in enantiomeric purity to a maximum ee value of 94 % (Figure 1). This increase in the ee value, along with the formation of the dialdehyde 3 (14 % after 24 h), suggested that the minor enantiomer (M)-2 produced in the enantioselective oxidation of 1 was ...

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“…This approach has been applied in the synthesis of new chirogenic binaphthylmonophosphines, 344 the monoxide of 2,2 0 -bis(diphenylphosphino)-1,1 0 -binaphthalene 345 and the chiral P,N-system (148). 346 Palladium-catalysed phosphination of bromoarenes and aryl triflates bearing a wide variety of functional groups has also been achieved by the use of triarylphosphines as the phosphinating reagent. 347,348 A microwave-assisted procedure for the palladium-or nickel-catalysed phosphination of aryl halides and triflates by diphenylphosphine has also been reported.…”

Section: Miscellaneous Methods Of Preparing Phosphinesmentioning

confidence: 99%

Phosphines and Related Tervalent Phosphorus Systems

2006

Organophosphorus Chemistry

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The ‘lactone method’: enantioselective preparation of novel P,N-biaryl ligands and their use in the synthesis of the biarylic alkaloids, ancistrotanzanine B and ancistroealaine A

Cited by 26 publications

References 54 publications

Sulfone “Geländer” Helices: Revealing Unexpected Parameters Controlling the Enantiomerization Process

Sulfone “Geländer” Helices: Revealing Unexpected Parameters Controlling the Enantiomerization Process

Biocatalytic Desymmetrization of an Atropisomer with both an Enantioselective Oxidase and Ketoreductases

Phosphines and Related Tervalent Phosphorus Systems

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