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Papers by venkatachalam angamuthu

Tetrahedron Letters, Feb 1, 2019

Chemico-Biological Interactions, 2019

Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered nati... more Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered native tree of Taiwan namely Cinnamomum kanehirai Hayata. It is used as a traditional medicine in Taiwan and has several health benefits including free radical scavenging, anti-inflammatory, antimicrobial, hepatoprotective, neuroprotective, antidiabetic, and free radical-induced DNA damage protecting activities. Antroquinonol is a tetrahydro ubiquinone derivative found predominately in the mycelium of Antrodia camphorata, and is characterized by numerous biological and pharmacological activities. Several studies have revealed potential anticancer effects of antroquinonol in various carcinogenic models. Moreover, a phase II clinical trial is ongoing in the US and Taiwan to treat the lung cancer patients with this active compound. The present review aims at depicting a detailed view of the synthetic procedures of antroquinonol as well as deciphering its potential health benefits with a special emphasis on anticancer properties.

ACS omega, Aug 1, 2017

Cyclopropanation using dimethylsulfoxonium methylide (Corey−Chaykovsky reaction) was examined wit... more Cyclopropanation using dimethylsulfoxonium methylide (Corey−Chaykovsky reaction) was examined with a series of linear α,β-unsaturated ketones, and the results showed that the major trajectory for the addition of the sulfur ylide to the enones is anti, related to the γ-substituent. The stereochemical assignment for the generated cyclopropanes was achieved by X-ray crystallography or comparing with the reported spectroscopic data. We found that the diastereoselectivity was influenced by several factors, including the protecting groups, solvents, and temperatures, and good anti/syn ratios (>10:1) were often obtained using the tert-butyldimethylsilyl and tert-butyldiphenylsilyl-protected substrates. The method was applied to a formal synthesis of a natural eicosanoid with good efficiency.

Organic Letters, Mar 2, 2020

Kijanose is one of the most highly functionalized deoxysugars found in nature and a challenging s... more Kijanose is one of the most highly functionalized deoxysugars found in nature and a challenging synthetic target. We found that the ring opening of trisubstituted, 2-oxazolidinone-fused aziridines is regio- and stereoselective, and the azide adduct has the same stereochemistry as that of kijanose after converting the azido to a nitro group. Therefore, both α- and β-methyl l-kijanosides were prepared from ethyl l-lactate in 14% total yield.

Catalysts, Feb 10, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Sustainable Chemistry and Pharmacy, Sep 1, 2019

Applied Catalysis A-general, Oct 1, 2015

Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have h... more Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have high surface-area that allows the design and setup of many catalytic sites. Their surfaces can be modified with chiral organocatalyst (COC) to become a sustainable catalytic material. This functionalized magnetite can be easily separated using an external magnet after reaction. We summarize the use of COC-MNPs which are robust and readily available for chiral transformation. The catalytic activity, recyclability, and immobilization method of COC-MNPs are described. The catalytic load, size of the particles, solvent system, ee values and de ratios are also evaluated on each asymmetric reaction.

Catalysts, 2021

Brucine diol (BD) catalyzed asymmetric Morita–Baylis–Hillman (MBH) reaction is observed for the f... more Brucine diol (BD) catalyzed asymmetric Morita–Baylis–Hillman (MBH) reaction is observed for the first time. Brucine N-oxide (BNO) was found to not have an effective chiral catalyst. Faster reaction rate was obtained using unsaturated ester or aromatic aldehydes in the presence of BNO. 4-Nitrobenzaldehyde and α,β-unsaturated ketone/ester were converted to the MBH adduct in moderate yields (up to 74%) with 70% ee value by this catalytic system. The mechanism of BD catalysis is probably initiated by conjugating the vicinal diol of BD to the carbonyl group of the aromatic aldehyde through hydrogen bonding. The tertiary amine of BD acts as a nucleophile to activate vinyl ketone for coupling with the carbonyl of aldehyde through an intramolecular carbonylated reaction. Finally, the breakdown of the complex caused the formation of the MBH adduct (a benzyl-allyl alcohol). The chirality of the benzyl-allyl alcohol is likely affected by the interaction of the bulky asymmetric plane of BD.

Journal of the American Chemical Society, 2020

Radical reduction of alkyl halides and aerobic oxidation of alkyl aromatics are reported using wa... more Radical reduction of alkyl halides and aerobic oxidation of alkyl aromatics are reported using water-soluble container compounds (1 and 2). The reductions involve -dihalides (4-8 and 10) with radical initiators in cavitand hosts with varied binding affinities. Product distributions lead to general guidelines for the use of dynamic supramolecular systems with fast reactions. Binding of guest substrates in the hosts must show high affinities (Ka > 103 M-1) to ensure that the reactions take place under confinement in the containers (11 and 12).

Molecules, 2020

The total synthesis of (−)-antrocin and its enantiomer are presented. Antrocin (−)-1 is an import... more The total synthesis of (−)-antrocin and its enantiomer are presented. Antrocin (−)-1 is an important natural product which acts as an antiproliferative agent in a metastatic breast cancer cell line (IC50: 0.6 μM). The key features of this synthesis are: (a) selective anti-addition of trimethylsilyl cyanide (TMSCN) to α,β-unsaturated ketone; (b) resolution of (±)-7 using chiral auxiliary L-dimethyl tartrate through formation of cyclic ketal diastereomers followed by simple column chromatography separation and acid hydrolysis; (c) substrate-controlled stereoselective aldol condensation of (+)-12 with monomeric formaldehyde and pyridinium chlorochromate (PCC) oxidation for synthesis of essential lactone core in (−)-14; and (d) non-basic Lombardo olefination of the carbonyl at the final step to yield (−)-antrocin. In addition, (+)-9 cyclic ketal diastereomer was converted to (+)-antrocin with similar reaction sequences.

Organic Chemistry Frontiers, 2019

The cavitand induced “yo-yo” motion was applied to mono-epoxidation reaction of α,ω-dienes using ... more The cavitand induced “yo-yo” motion was applied to mono-epoxidation reaction of α,ω-dienes using N-bromosuccinamide and K2CO3 in D2O.

Sustainable Chemistry and Pharmacy, 2019

Chiral amine and their derivatives have been proved to be powerful organocatalysts for asymmetric... more Chiral amine and their derivatives have been proved to be powerful organocatalysts for asymmetric transformations. There is a trend to combine organocatalyst with sustainable matrix, such as, magnetic nanoparticles (MNPs) to form a selective and recyclable catalyst. Therefore, silica-coated Fe 3 O 4 MNP was fabricated to establish a large macrocycle with glutamate (MNP-17 and 18), Pro-Glu (MNP-21), or cyclohexyl-1,2-diamine (MNP-28, 29, and 30). Their bifunctional enamine activities were evaluated with direct aldol reaction. Among them, MNP-30 having the largest macrocyclic ring and the longest lipophilic chain achieved better yield and ee value (up to 96%). It seems the affinity toward substrate was enhanced by the macrocyclic effect. The rigidity of cyclohexyl-1,2-diamine contributed the enantioselectivity. Moreover, MNP-30 is recyclable and stayed on high activity and enantioselectivity after 3 recycles.

Organic & Biomolecular Chemistry, 2019

Host–guest complexation of α,ω-dibromides showed rabid tumbling conformation on NMR timescales an... more Host–guest complexation of α,ω-dibromides showed rabid tumbling conformation on NMR timescales and afforded mono hydroxyl bromides after hydrolysis in D2O.

Tetrahedron Letters, 2019

Chemico-Biological Interactions, 2019

Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered nati... more Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered native tree of Taiwan namely Cinnamomum kanehirai Hayata. It is used as a traditional medicine in Taiwan and has several health benefits including free radical scavenging, anti-inflammatory, antimicrobial, hepatoprotective, neuroprotective, antidiabetic, and free radical-induced DNA damage protecting activities. Antroquinonol is a tetrahydro ubiquinone derivative found predominately in the mycelium of Antrodia camphorata, and is characterized by numerous biological and pharmacological activities. Several studies have revealed potential anticancer effects of antroquinonol in various carcinogenic models. Moreover, a phase II clinical trial is ongoing in the US and Taiwan to treat the lung cancer patients with this active compound. The present review aims at depicting a detailed view of the synthetic procedures of antroquinonol as well as deciphering its potential health benefits with a special emphasis on anticancer properties.

Asian Journal of Organic Chemistry, 2016

A sequence of vinylalumination of α‐substituted aldehydes, ring‐closing metathesis (RCM), and pal... more A sequence of vinylalumination of α‐substituted aldehydes, ring‐closing metathesis (RCM), and palladium‐catalyzed allylic substitution was utilized to prepare the biologically active natural products, pericosines, from d‐ribose. The anti‐adduct of vinylalumination was transformed into pericosine A after RCM, removal of the 4‐methoxybenzyl protecting group, and chlorination. The diacetate of the anti‐adduct was converted to pericosine C after the palladium‐catalyzed, SN2′‐type, allylic substitution. However, an unexpected dimeric product was generated in utilizing this approach to prepare pericosine E.

Applied Catalysis A: General, 2015

Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have h... more Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have high surface-area that allows the design and setup of many catalytic sites. Their surfaces can be modified with chiral organocatalyst (COC) to become a sustainable catalytic material. This functionalized magnetite can be easily separated using an external magnet after reaction. We summarize the use of COC-MNPs which are robust and readily available for chiral transformation. The catalytic activity, recyclability, and immobilization method of COC-MNPs are described. The catalytic load, size of the particles, solvent system, ee values and de ratios are also evaluated on each asymmetric reaction.

Tetrahedron Letters, Feb 1, 2019

Chemico-Biological Interactions, 2019

Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered nati... more Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered native tree of Taiwan namely Cinnamomum kanehirai Hayata. It is used as a traditional medicine in Taiwan and has several health benefits including free radical scavenging, anti-inflammatory, antimicrobial, hepatoprotective, neuroprotective, antidiabetic, and free radical-induced DNA damage protecting activities. Antroquinonol is a tetrahydro ubiquinone derivative found predominately in the mycelium of Antrodia camphorata, and is characterized by numerous biological and pharmacological activities. Several studies have revealed potential anticancer effects of antroquinonol in various carcinogenic models. Moreover, a phase II clinical trial is ongoing in the US and Taiwan to treat the lung cancer patients with this active compound. The present review aims at depicting a detailed view of the synthetic procedures of antroquinonol as well as deciphering its potential health benefits with a special emphasis on anticancer properties.

ACS omega, Aug 1, 2017

Cyclopropanation using dimethylsulfoxonium methylide (Corey−Chaykovsky reaction) was examined wit... more Cyclopropanation using dimethylsulfoxonium methylide (Corey−Chaykovsky reaction) was examined with a series of linear α,β-unsaturated ketones, and the results showed that the major trajectory for the addition of the sulfur ylide to the enones is anti, related to the γ-substituent. The stereochemical assignment for the generated cyclopropanes was achieved by X-ray crystallography or comparing with the reported spectroscopic data. We found that the diastereoselectivity was influenced by several factors, including the protecting groups, solvents, and temperatures, and good anti/syn ratios (>10:1) were often obtained using the tert-butyldimethylsilyl and tert-butyldiphenylsilyl-protected substrates. The method was applied to a formal synthesis of a natural eicosanoid with good efficiency.

Organic Letters, Mar 2, 2020

Kijanose is one of the most highly functionalized deoxysugars found in nature and a challenging s... more Kijanose is one of the most highly functionalized deoxysugars found in nature and a challenging synthetic target. We found that the ring opening of trisubstituted, 2-oxazolidinone-fused aziridines is regio- and stereoselective, and the azide adduct has the same stereochemistry as that of kijanose after converting the azido to a nitro group. Therefore, both α- and β-methyl l-kijanosides were prepared from ethyl l-lactate in 14% total yield.

Catalysts, Feb 10, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Sustainable Chemistry and Pharmacy, Sep 1, 2019

Applied Catalysis A-general, Oct 1, 2015

Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have h... more Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have high surface-area that allows the design and setup of many catalytic sites. Their surfaces can be modified with chiral organocatalyst (COC) to become a sustainable catalytic material. This functionalized magnetite can be easily separated using an external magnet after reaction. We summarize the use of COC-MNPs which are robust and readily available for chiral transformation. The catalytic activity, recyclability, and immobilization method of COC-MNPs are described. The catalytic load, size of the particles, solvent system, ee values and de ratios are also evaluated on each asymmetric reaction.

Catalysts, 2021

Brucine diol (BD) catalyzed asymmetric Morita–Baylis–Hillman (MBH) reaction is observed for the f... more Brucine diol (BD) catalyzed asymmetric Morita–Baylis–Hillman (MBH) reaction is observed for the first time. Brucine N-oxide (BNO) was found to not have an effective chiral catalyst. Faster reaction rate was obtained using unsaturated ester or aromatic aldehydes in the presence of BNO. 4-Nitrobenzaldehyde and α,β-unsaturated ketone/ester were converted to the MBH adduct in moderate yields (up to 74%) with 70% ee value by this catalytic system. The mechanism of BD catalysis is probably initiated by conjugating the vicinal diol of BD to the carbonyl group of the aromatic aldehyde through hydrogen bonding. The tertiary amine of BD acts as a nucleophile to activate vinyl ketone for coupling with the carbonyl of aldehyde through an intramolecular carbonylated reaction. Finally, the breakdown of the complex caused the formation of the MBH adduct (a benzyl-allyl alcohol). The chirality of the benzyl-allyl alcohol is likely affected by the interaction of the bulky asymmetric plane of BD.

Journal of the American Chemical Society, 2020

Radical reduction of alkyl halides and aerobic oxidation of alkyl aromatics are reported using wa... more Radical reduction of alkyl halides and aerobic oxidation of alkyl aromatics are reported using water-soluble container compounds (1 and 2). The reductions involve -dihalides (4-8 and 10) with radical initiators in cavitand hosts with varied binding affinities. Product distributions lead to general guidelines for the use of dynamic supramolecular systems with fast reactions. Binding of guest substrates in the hosts must show high affinities (Ka > 103 M-1) to ensure that the reactions take place under confinement in the containers (11 and 12).

Molecules, 2020

The total synthesis of (−)-antrocin and its enantiomer are presented. Antrocin (−)-1 is an import... more The total synthesis of (−)-antrocin and its enantiomer are presented. Antrocin (−)-1 is an important natural product which acts as an antiproliferative agent in a metastatic breast cancer cell line (IC50: 0.6 μM). The key features of this synthesis are: (a) selective anti-addition of trimethylsilyl cyanide (TMSCN) to α,β-unsaturated ketone; (b) resolution of (±)-7 using chiral auxiliary L-dimethyl tartrate through formation of cyclic ketal diastereomers followed by simple column chromatography separation and acid hydrolysis; (c) substrate-controlled stereoselective aldol condensation of (+)-12 with monomeric formaldehyde and pyridinium chlorochromate (PCC) oxidation for synthesis of essential lactone core in (−)-14; and (d) non-basic Lombardo olefination of the carbonyl at the final step to yield (−)-antrocin. In addition, (+)-9 cyclic ketal diastereomer was converted to (+)-antrocin with similar reaction sequences.

Organic Chemistry Frontiers, 2019

The cavitand induced “yo-yo” motion was applied to mono-epoxidation reaction of α,ω-dienes using ... more The cavitand induced “yo-yo” motion was applied to mono-epoxidation reaction of α,ω-dienes using N-bromosuccinamide and K2CO3 in D2O.

Sustainable Chemistry and Pharmacy, 2019

Chiral amine and their derivatives have been proved to be powerful organocatalysts for asymmetric... more Chiral amine and their derivatives have been proved to be powerful organocatalysts for asymmetric transformations. There is a trend to combine organocatalyst with sustainable matrix, such as, magnetic nanoparticles (MNPs) to form a selective and recyclable catalyst. Therefore, silica-coated Fe 3 O 4 MNP was fabricated to establish a large macrocycle with glutamate (MNP-17 and 18), Pro-Glu (MNP-21), or cyclohexyl-1,2-diamine (MNP-28, 29, and 30). Their bifunctional enamine activities were evaluated with direct aldol reaction. Among them, MNP-30 having the largest macrocyclic ring and the longest lipophilic chain achieved better yield and ee value (up to 96%). It seems the affinity toward substrate was enhanced by the macrocyclic effect. The rigidity of cyclohexyl-1,2-diamine contributed the enantioselectivity. Moreover, MNP-30 is recyclable and stayed on high activity and enantioselectivity after 3 recycles.

Organic & Biomolecular Chemistry, 2019

Host–guest complexation of α,ω-dibromides showed rabid tumbling conformation on NMR timescales an... more Host–guest complexation of α,ω-dibromides showed rabid tumbling conformation on NMR timescales and afforded mono hydroxyl bromides after hydrolysis in D2O.

Tetrahedron Letters, 2019

Chemico-Biological Interactions, 2019

Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered nati... more Antrodia camphorata is an expensive mushroom that grows on the inner cavity of an endangered native tree of Taiwan namely Cinnamomum kanehirai Hayata. It is used as a traditional medicine in Taiwan and has several health benefits including free radical scavenging, anti-inflammatory, antimicrobial, hepatoprotective, neuroprotective, antidiabetic, and free radical-induced DNA damage protecting activities. Antroquinonol is a tetrahydro ubiquinone derivative found predominately in the mycelium of Antrodia camphorata, and is characterized by numerous biological and pharmacological activities. Several studies have revealed potential anticancer effects of antroquinonol in various carcinogenic models. Moreover, a phase II clinical trial is ongoing in the US and Taiwan to treat the lung cancer patients with this active compound. The present review aims at depicting a detailed view of the synthetic procedures of antroquinonol as well as deciphering its potential health benefits with a special emphasis on anticancer properties.

Asian Journal of Organic Chemistry, 2016

A sequence of vinylalumination of α‐substituted aldehydes, ring‐closing metathesis (RCM), and pal... more A sequence of vinylalumination of α‐substituted aldehydes, ring‐closing metathesis (RCM), and palladium‐catalyzed allylic substitution was utilized to prepare the biologically active natural products, pericosines, from d‐ribose. The anti‐adduct of vinylalumination was transformed into pericosine A after RCM, removal of the 4‐methoxybenzyl protecting group, and chlorination. The diacetate of the anti‐adduct was converted to pericosine C after the palladium‐catalyzed, SN2′‐type, allylic substitution. However, an unexpected dimeric product was generated in utilizing this approach to prepare pericosine E.

Applied Catalysis A: General, 2015

Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have h... more Abstract Magnetic nanoparticles (MNPs) have been widely used as a catalytic supports. MNPs have high surface-area that allows the design and setup of many catalytic sites. Their surfaces can be modified with chiral organocatalyst (COC) to become a sustainable catalytic material. This functionalized magnetite can be easily separated using an external magnet after reaction. We summarize the use of COC-MNPs which are robust and readily available for chiral transformation. The catalytic activity, recyclability, and immobilization method of COC-MNPs are described. The catalytic load, size of the particles, solvent system, ee values and de ratios are also evaluated on each asymmetric reaction.