Raney Nickel–Catalyzed Hydrogenation of Unsaturated Carboxylic Acids with Sodium Borohydride in Water

Rao, Gopal Krishna; Gowda, Narendra B.; Ramakrishna, Ramesha

doi:10.1080/00397911.2010.533239

Cited by 16 publications

(10 citation statements)

References 23 publications

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“…1 Dihydro-6-hydroxyferulic acid and dihydro-2-hydroxy-p-coumaric acid were obtained by stirring scopoletin (80 mg) for 1 h in 2 M NaOH solution at 80°C. Similar to the synthesis of dihydrocinnamic acid (3-phenylpropanoic acid) from cinnamic acid described by Rao and coworkers 38 , we then added Raney nickel (60 mg, W6 grade) and sodium borohydride (40 mg) to the reaction mixture, after which the reaction mixture was acidified to pH 5 with 1 M HCl and extracted in EtOAc. EtOAc was subsequently removed in a SpeedVac.…”

Section: Methodsmentioning

confidence: 99%

COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins

et al. 2019

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Coumarins or 1,2-benzopyrones comprise a large class of secondary metabolites ubiquitously found in the plant kingdom. In many plant species, coumarins are particularly important for iron acquisition and plant defense. Here we show that COUMARIN SYNTHASE (COSY) is a key enzyme in the biosynthesis of coumarins. Arabidopsis thaliana cosy mutants are strongly reduced in coumarin levels and accumulate ohydroxyphenylpropanoids instead. Accordingly, cosy mutants have reduced iron content and show growth defects when grown under conditions where iron availability is limited. Recombinant COSY is able to produce umbelliferone, esculetin and scopoletin from their respective o-hydroxycinnamoyl-CoA thioesters via two reaction steps: a trans-cis isomerization followed by a lactonization. This conversion happens partially spontaneously and is catalyzed by light, which explains why the need for an enzyme for this conversion has been overlooked. The combined results show that COSY has an essential role in the biosynthesis of coumarins in organs that are shielded from light, such as roots. These findings provide routes to improving coumarin production in crops or via microbial fermentation.

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Section: Methodsmentioning

confidence: 99%

COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins

et al. 2019

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“…Toddanolic acid ( 7 ) is structurally related to toddalolactone ( 15 ). An artifactual formation of 7 can be ruled out given that an opening of the lactone ring and reduction of the double bond would require conditions (e.g., basic pH, metal catalyst, and NaBH 4 ) far from the ones used during the isolation. , …”

Section: Resultsmentioning

confidence: 99%

Compounds fromToddalia asiatica: Immunosuppressant Activity and Absolute Configurations

et al. 2020

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In a screening of an extract library from plants used in Traditional Chinese Medicine the MeOH extract of Toddalia asiatica inhibited proliferation of human primary T cells with an IC50 of 25.8 μg/mL. Activity in the extract was tracked by HPLC activity profiling, and a total of 15 compounds were characterized. Three compounds, toddalic acid (6) and both enantiomers (7a and 7b) of toddanolic acid (7), were new natural products, and two recently published compounds, (2′R)-toddalolactone 3′-O-β-d-glucopyranoside (10) and (2′S)-toddalolactone 2′-O-β-d-glucopyranoside (11), were described in detail for the first time. The absolute configurations of compounds 8, 9, 10, 12, 13, and 15 were determined by comparison of experimental and calculated ECD spectra. For glucosides 9 and 10, ECD data and chiral-phase HPLC of the aglycones after enzymatic hydrolysis confirmed the results. Nitidine chloride (4) inhibited proliferation of primary human T cells with an IC50 of 0.4 μM.

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“…A classic hydrogenation with H 2 /PdÀ C (PH 2 = 1 atm) gave no result in methanol and the starting material was recovered after 12 hours at 50°C. Further reagents such as NaBH 3 CN, NaBH 4 and NaBH 4 coupled with other reagents (NaBH 4 + Pyridine; [20] NaBH 4 + Ni Raney [21] ) were used. The reaction time and temperature were varied but no reaction could be observed.…”

Section: Introductionmentioning

confidence: 99%

Exploring Coumarins Reduction: NaBH₄/MeOH versus Nickel Boride Generated In Situ.

et al. 2020

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The role of reagents NaBH4/MeOH and nickel boride (Ni2B) generated in situ from NaBH4 and NiCl2, are compared in the reduction process of coumarin and a variety of 3,7‐substituted coumarins bearing electro‐donating (ED‐group) or electro‐withdrawing groups (EW‐group). Coumarins (chromen‐2‐ones) are only reduced by Ni2B to the cyclic chromanones. This provides a useful and very simple reduction method for electron‐rich coumarins, which are resistant to many other reducing methods. DFT calculations underlined the role of substituents electronic effects in the reactivity. Subsequent methanolysis may open the ring to methyl phenylpropanoate esters and alcohols resulting from their reductions can also be produced.

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Raney Nickel–Catalyzed Hydrogenation of Unsaturated Carboxylic Acids with Sodium Borohydride in Water

Cited by 16 publications

References 23 publications

COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins

COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins

Compounds fromToddalia asiatica: Immunosuppressant Activity and Absolute Configurations

Exploring Coumarins Reduction: NaBH₄/MeOH versus Nickel Boride Generated In Situ.

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Raney Nickel–Catalyzed Hydrogenation of Unsaturated Carboxylic Acids with Sodium Borohydride in Water

Cited by 16 publications

References 23 publications

COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins

COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins

Compounds fromToddalia asiatica: Immunosuppressant Activity and Absolute Configurations

Exploring Coumarins Reduction: NaBH4/MeOH versus Nickel Boride Generated In Situ.

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Exploring Coumarins Reduction: NaBH₄/MeOH versus Nickel Boride Generated In Situ.