The neoflavanoid group of natural products—I

Eyton, W.B.; Ollis, W. D.; Sutherland, I. O.; Gottlieb, Otto R.; Magalhães, Mauro Taveira; Jackman, L. M.

doi:10.1016/s0040-4020(01)93924-9

Cited by 81 publications

(42 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The synthetic utility of the present method was further demonstrated in the asymmetric synthesis of intermediates for the natural products (R)-(+)-4-methoxydalbergione [20] and (S)-cherylline, [1d] as well as an anti-viral (smallpox) agent (À)-6, [21] with the hydrogenation products (R)-2 m, (S)-2 s, and (+)-2 t, respectively, as the starting materials (Scheme 1). Reduction of (R)-2 m with LiAlH 4 at room [b] (E)-1 i 2-FC 6 H 4 Ph 2 i 91 (R) 10 [b] (E)-1 j 2-ClC 6 H 4 Ph 2 j 85 (R) 11 [b] (E)-1 k 2-MeOC 6 H 4 Ph 2 k 92 (R) 12 [c] (E)-1 l 2-BnOC 6 H 4 Ph 2 l 95 (+) 13 [b] (E)-1 m 2,4-(MeO) 2 C 6 H 3 Ph 2 m 94 (R) 14 [b] …”

mentioning

confidence: 88%

Rhodium(I)‐Catalyzed Enantioselective Hydrogenation of Substituted Acrylic Acids with Sterically Similar β,β‐Diaryls

Li¹,

Dong²,

Wang³

et al. 2013

Angew Chem Int Ed

View full text Add to dashboard Cite

Dedicated to Professor Guo-Qiang Lin on the occasion of his 70th birthdayOptically active b,b-diarylpropionic acids are a class of important building blocks for the asymmetric synthesis of chiral diarylmethine compounds, [1] which are structural moieties that are found in many pharmaceuticals and bioactive compounds, including the therapeutically important molecules tolterodine, [1a-b] sertraline, [1c] indatraline, [1d] and natural products, such as cherylline.[1e]Thus far, methods for the asymmetric synthesis of chiral b,b-diarylpropionic acids often involve a multistep sequence and/or stoichiometric transformation using chiral auxiliaries, [2] only a few examples of catalytic asymmetric methods, including Rh I -or Cu II -catalyzed reduction of b,b-diaryl unsaturated acrylates [3,4] or nitriles [5] using either polymethylhydrosiloxanes or diethoxymethylsilane as the reductants, and Rh I -catalyzed 1,4-addition of organoboron reagents to arylidene Meldrums acids, [6] have been reported to provide the corresponding b,b-diaryl propanoates or propanenitriles with good to high enantioselectivities. In terms of atom economy and environmental concerns, asymmetric hydrogenation of b,b-diarylacrylates with molecular H 2 is more advantageous. In this respect, Ir I -or Rh I -catalyzed asymmetric hydrogenation of trisubstituted olefins for the formation of diarylmethine stereogenic centers seems feasible. [7] However, reactions involving 3,3-diarylacrylates (especially free acids) proved to be challenging, as only moderate enantioselectivities were obtained, in most cases under high pressure (100 bar). Herein, we present the results of the development of an efficient asymmetric hydrogenation of b,b-diarylacrylic acids in the presence of a Rh complex based on the heterocombination of a chiral monodentate secondary phosphine oxide (SPO) preligand and an achiral monodentate phosphine ligand as the catalyst to afford a wide variety of the corresponding b,b-diarylpropionic acids with biological importance in excellent optical purities.The most challenging issue associated with the control of stereochemistry in the asymmetric hydrogenation of b,bdiarylacrylic acids is the differentiation of a stereogenic center with two sterically similar aryl groups at the b-position of acrylic acids. [3][4][5][6][7][8] Very recently, we disclosed that Rh I catalysts generated in situ by interaction with SPO preligands demonstrated excellent performance in the asymmetric hydrogenation of a-substituted ethenylphosphonic acids.[9] The salient features of SPO ligands, including ready accessibility, good air and moisture stability, and the potentially H-bonding OH group in the ligand, [9,10] prompted us to explore the catalytic potential of Rh I /SPO systems in the asymmetric hydrogenation of challenging b,b-diarylacrylic acid substrates. As shown in Table 1, chiral monodentate SPO preligands L1-L7 were evaluated in the rhodium-catalyzed asymmetric hydrogenation of (E)-3-phenyl-3-(p-tolyl) acrylic acid ((E)-1 a). However, an initial screening of ...

show abstract

mentioning

confidence: 88%

Rhodium(I)‐Catalyzed Enantioselective Hydrogenation of Substituted Acrylic Acids with Sterically Similar β,β‐Diaryls

Li¹,

Dong²,

Wang³

et al. 2013

Angew Chem Int Ed

View full text Add to dashboard Cite

show abstract

“…Thus, hydrogenation gives the phenol (47a) and titration with cold alkali yields the hydrate (47b), the cyclopropane ring reacting like a double bond in the now familiar manner. The reactions of fuscin leave no doubt that it exists in the quinone methide form (42) rather than in the tautomeric o-quinone form (48). BARTON and HENDRICKSON (4) have confirmed the structure (42) for fuscin by a synthesis starting from methyl 3.4,s-trimethoxyphenylacetate.…”

Section: Fuscinmentioning

confidence: 99%

“…The tendency for the reaction to occur increases as the quinone ring becomes more highly substituted by electron-donating groups. The co-occurrence (47,48) of dalbergiones (1°7) and dalbergins (109) may be due to a similar cyclisation of the intermediate (108) …”

Section: R (1°3)mentioning

confidence: 99%

Quinone Methides in Nature

Turner

1966

Fortschritte Der Chemie Organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products / Progrès Dans La Chimi

View full text Add to dashboard Cite

“…Similarly, HMBC correlations from H-2¢ and H-6¢ of ABCX system of ring B to C-7 implied that the hydroxyl group is located at C-3¢ and linked ring B with C-7. The absolute configuration at position 7 was determined to be S by comparing its [a] D and stopped-flow LC-CD spectral data with those of related compounds [7]. From this evidence, we concluded that 1 is (S)-3¢-hydroxy-4-methoxydalbergione.…”

Section: Resultsmentioning

confidence: 96%

“…The HMBC correlations from H-6¢ and H-1¢ in the ABX system to C-7 and C-4¢ confirmed the position of hydroxyl groups at C-3¢ and C-4¢, with the other HMBC correlations in 2 being the same as those in 1. The absolute configuration 7S was determined by comparing its [a] D and stopped-flow LC-CD spectral data with those of related compounds [7].…”

Section: Resultsmentioning

confidence: 99%