Search results for: Arun K. Ghosh

Items from 1 to 20 out of 146 results

article

Asymmetric 1,2‐Carbamoyl Rearrangement of Lithiated Chiral Oxazolidine Carbamates and Diastereoselective Synthesis of α‐Hydroxy Amides

Arun K. Ghosh, Amartyo J. Basu, Che‐Sheng Hsu, Monika Yadav

Chemistry – A European Journal > 28 > 43 > n/a - n/a

Asymmetric 1,2‐carbamoyl rearrangement of lithiated 2‐alkenyl carbamates has been investigated. Deprotonation of chiral 2‐alkenyl oxazolidine carbamates with sec‐butyllithium in ether at −78 °C followed by warming of the resulting 1‐lithio‐2‐alkenyl derivatives to room temperature resulted in 1,2‐carbamoyl rearrangement to provide α‐hydroxy amides. The rearrangement proceeded with excellent diastereoselectivity...

article

Design, synthesis, X-ray studies, and biological evaluation of novel BACE1 inhibitors with bicyclic isoxazoline carboxamides as the P3 ligand

Arun K. Ghosh, Koena Ghosh, Margherita Brindisi, Emma K. Lendy, more

Bioorganic & Medicinal Chemistry Letters > 2018 > 28 > 15 > 2605-2610

We describe the design, synthesis, X-ray studies, and biological evaluation of novel BACE1 inhibitors containing bicyclic isoxazoline carboxamides as the P3 ligand in combination with methyl cysteine, methylsulfonylalanine and Boc-amino alanine as P2 ligands. Inhibitor 3a displayed a BACE1 K_i value of 10.9 nM and EC₅₀ of 343 nM. The X-ray structure of 3a bound to the active site of BACE1 was determined...

article

Design, synthesis, X-ray studies, and biological evaluation of novel macrocyclic HIV-1 protease inhibitors involving the P1′-P2′ ligands

Arun K. Ghosh, W. Sean Fyvie, Margherita Brindisi, Melinda Steffey, more

Bioorganic & Medicinal Chemistry Letters > 2017 > 27 > 21 > 4925-4931

Design, synthesis, and evaluation of a new class of HIV-1 protease inhibitors containing diverse flexible macrocyclic P1′-P2′ tethers are reported. Inhibitor 5a with a pyrrolidinone-derived macrocycle exhibited favorable enzyme inhibitory and antiviral activity (K_i=13.2nM, IC₅₀=22nM). Further incorporation of heteroatoms in the macrocyclic skeleton provided macrocyclic inhibitors 5m and 5o. These...

article

Design of novel HIV-1 protease inhibitors incorporating isophthalamide-derived P2-P3 ligands: Synthesis, biological evaluation and X-ray structural studies of inhibitor-HIV-1 protease complex

Arun K. Ghosh, Margherita Brindisi, Prasanth R. Nyalapatla, Jun Takayama, more

Bioorganic & Medicinal Chemistry > 2017 > 25 > 19 > 5114-5127

Based upon molecular insights from the X-ray structures of inhibitor-bound HIV-1 protease complexes, we have designed a series of isophthalamide-derived inhibitors incorporating substituted pyrrolidines, piperidines and thiazolidines as P2-P3 ligands for specific interactions in the S2-S3 extended site. Compound 4b has shown an enzyme K_i of 0.025nM and antiviral IC₅₀ of 69nM. An X-ray crystal structure...

article

An enantioselective enzymatic desymmetrization route to hexahydro-4H-furopyranol, a high-affinity ligand for HIV-1 protease inhibitors

Arun K. Ghosh, Anindya Sarkar

Tetrahedron Letters > 2017 > 58 > 33 > 3230-3233

An enantioselective synthesis of (3aS,4S,7aR)-hexahydro-4H-furo[2,3-b]pyran-4-ol, a high-affinity nonpeptide ligand for a variety of potent HIV-1 protease inhibitors is described. The key steps involved a highly enantioselective enzymatic desymmetrization of meso-diacetate, an efficient transacetalization, and a highly diastereoselective reduction of a ketone. This route is amenable to large-scale...

article

Design, synthesis, and X-ray structural studies of BACE-1 inhibitors containing substituted 2-oxopiperazines as P1′-P2′ ligands

Arun K. Ghosh, Margherita Brindisi, Yu-Chen Yen, Emilio L. Cárdenas, more

Bioorganic & Medicinal Chemistry Letters > 2017 > 27 > 11 > 2432-2438

We report the design and synthesis of a series of BACE1 inhibitors incorporating mono- and bicyclic 6-substituted 2-oxopiperazines as novel P1′ and P2′ ligands and isophthalamide derivative as P2-P3 ligands. Among mono-substituted 2-oxopiperazines, inhibitor 5a with N-benzyl-2-oxopiperazine and isophthalamide showed potent BACE1 inhibitory activity (K_i=2nM). Inhibitor 5g, with N-benzyl-2-oxopiperazine...

article

Total syntheses of both enantiomers of amphirionin 4: A chemoenzymatic based strategy for functionalized tetrahydrofurans

Arun K. Ghosh, Prasanth R. Nyalapatla

Tetrahedron > 2017 > 73 > 14 > 1820-1830

The total syntheses of (−)-amphirionin-4 and (+)-amphirionin-4 have been achieved in a convergent and enantioselective manner. The tetrahydrofuranol cores of amphirionin-4 were constructed in optically active form by enzymatic resolution of racemic cis-3-hydroxy-5-methyldihydrofuran-2(3H)-one. The polyene side chain was efficiently synthesized using Stille coupling. The remote C8-stereocenter was...

article

A fission yeast cell-based system for multidrug resistant HIV-1 proteases

Zsigmond Benko, Dong Liang, Ge Li, Robert T. Elder, more

Cell & Bioscience > 2017 > 7 > 1 > 1-15

Background HIV-1 protease (PR) is an essential enzyme for viral production. Thus, PR inhibitors (PIs) are the most effective class of anti-HIV drugs. However, the main challenge to the successful use of PI drugs in patient treatment is the emergence of multidrug resistant PRs (_mdrPRs). This study aimed to develop a fission yeast cell-based system for rapid testing of new PIs that combat _mdrPRs. ...

article

Enantioselective Syntheses of (–)‐Alloyohimbane and (–)‐Yohimbane by an Efficient Enzymatic Desymmetrization Process

Arun K. Ghosh, Anindya Sarkar

European Journal of Organic Chemistry > 2016 > 36 > 6001 - 6009

Enantioselective syntheses of (–)‐alloyohimbane and (–)‐yohimbane were accomplished in a convergent manner. The key step involves a modified mild protocol for the enantioselective enzymatic desymmetrization of a meso‐diacetate. This provides convenient access to an optically active monoacetate in multi‐gram quantities and in high enantiomeric purity. This monoacetate was converted to (–)‐alloyohimbane...

article

An enantioselective synthesis of the C3–C21 segment of the macrolide immunosuppressive agent FR252921

Arun K. Ghosh, Samuel Rodriguez

Tetrahedron Letters > 2016 > 57 > 26 > 2884-2887

An enantioselective synthesis of the C3–C21 segment of the novel immunosuppressant FR252921 is described. The C12 and C13 stereogenic centers were constructed by a non-aldol process utilizing optically active 4-phenylbutyrolactone. The C18 stereogenic center was installed using Braun’s highly diastereoselective acetate aldol reaction. Other key steps involved Curtius rearrangement and Horner–Wadsworth–Emmons...

article

X-ray structure and inhibition of the feline infectious peritonitis virus 3C-like protease: Structural implications for drug design

Sarah E. St. John, Matthew D. Therkelsen, Prasanth R. Nyalapatla, Heather L. Osswald, more

Bioorganic & Medicinal Chemistry Letters > 2015 > 25 > 22 > 5072-5077

Feline infectious peritonitis (FIP) is a deadly disease that effects both domestic and wild cats and is caused by a mutation in feline coronavirus (FCoV) that allows the virus to replicate in macrophages. Currently, there are no treatments or vaccines available for the treatment of FIP even though it kills approximately 5% of cats in multi-cat households per year. In an effort to develop small molecule...

article

Structure-based design, synthesis, X-ray studies, and biological evaluation of novel HIV-1 protease inhibitors containing isophthalamide-derived P2-ligands

Arun K. Ghosh, Jun Takayama, Luke A. Kassekert, Jean-Rene Ella-Menye, more

Bioorganic & Medicinal Chemistry Letters > 2015 > 25 > 21 > 4903-4909

We describe the design, synthesis and biological evaluation of a series of novel HIV-1 protease inhibitors bearing isophthalamide derivatives as the P2–P3 ligands. We have investigated a range of acyclic and heterocyclic amides as the extended P2–P3 ligands. These inhibitors displayed good to excellent HIV-1 protease inhibitory activity. Also, a number of inhibitors showed very good antiviral activity...

article

Enantioselective synthesis of dioxatriquinane structural motifs for HIV-1 protease inhibitors using a cascade radical cyclization

Arun K. Ghosh, Chun-Xiao Xu, Heather L. Osswald

Tetrahedron Letters > 2015 > 56 > 23 > 3314-3317

Synthesis of novel HIV-1 protease inhibitors incorporating dioxatriquinane-derived P2-ligands is described. The tricyclic ligand alcohol contains five contiguous chiral centers. The ligand alcohols were prepared in optically active form by an enzymatic asymmetrization of mesodiacetate, cascade radical cyclization, and Lewis acid catalyzed reduction as the key steps. Inhibitors with dioxatriquinane-derived...

article

Structural and biological evaluation of a novel series of benzimidazole inhibitors of Francisella tularensis enoyl-ACP reductase (FabI)

Shahila Mehboob, Jinhua Song, Kirk E. Hevener, Pin-Chih Su, more

Bioorganic & Medicinal Chemistry Letters > 2015 > 25 > 6 > 1292-1296

Francisella tularensis, the causative agent of tularemia, presents a significant biological threat and is a Category A priority pathogen due to its potential for weaponization. The bacterial FASII pathway is a viable target for the development of novel antibacterial agents treating Gram-negative infections. Here we report the advancement of a promising series of benzimidazole FabI (enoyl-ACP reductase)...

article

Structure-based design, synthesis and biological evaluation of novel β-secretase inhibitors containing a pyrazole or thiazole moiety as the P3 ligand

Arun K. Ghosh, Margherita Brindisi, Yu-Chen Yen, Xiaoming Xu, more

Bioorganic & Medicinal Chemistry Letters > 2015 > 25 > 3 > 668-672

We describe structure-based design, synthesis, and biological evaluation of a series of novel inhibitors bearing a pyrazole (compounds 3a–h) or a thiazole moiety (compounds 4a–e) as the P3 ligand. We have also explored Boc-β-amino-l-alanine as a novel P2 ligand. A number of inhibitors have displayed β-secretase inhibitory potency. Inhibitor 4c has shown potent BACE1 inhibitory activity, K _i ...

article

A Convergent Synthesis of Carbocyclic Sinefungin and its C‐5 Epimer

Arun K. Ghosh, Kai Lv

European Journal of Organic Chemistry > 2014 > 30 > 6761 - 6768

A convergent synthesis of carbocyclic sinefungin (2), its C‐5 epimer 3a, and adenine‐modified derivative 3b is described. The key features of our approach include the use of commercially available L‐methionine and readily available (1R,4S)‐4‐hydroxy‐2‐cyclopentenyl acetate as starting materials, a cross‐metathesis reaction, an enzymatic kinetic resolution, and a Staudinger reduction. The current synthesis...

article

An enantioselective synthesis of a MEM-protected aetheramide A derivative

Arun K. Ghosh, Kalapala Venkateswara Rao, Siddhartha Akasapu

Tetrahedron Letters > 2014 > 55 > 37 > 5191-5194

Aetheramides A and B are very potent anti-HIV agents. An enantioselective synthesis of a MEM-protected aetheramide A derivative is described. The synthesis was accomplished in a convergent and stereoselective manner. The key reactions involved asymmetric dihydroxylation, asymmetric allylation, asymmetric syn-aldol reactions, and asymmetric hydrogenation.

article

FeCl3-catalyzed tandem Prins and Friedel–Crafts cyclization: a highly diastereoselective route to polycyclic ring structures

Arun K. Ghosh, Chad Keyes, Anne M. Veitschegger

Tetrahedron Letters > 2014 > 55 > 30 > 4251-4254

Catalytic FeCl₃ in the presence of 4Å molecular sieves has been shown to effect highly diastereoselective tandem Prins and Friedel–Crafts cyclization of substituted (E/Z)-6-phenylhex-3-en-1-ol and a variety of aldehydes to provide a range of polycyclic compounds in good to excellent yields. The reaction of an enantioenriched alcohol with an aldehyde provided the cyclization product without loss of...

article

Bifunctional cinchona alkaloid-squaramide-catalyzed highly enantioselective aza-Michael addition of indolines to α,β-unsaturated ketones

Arun K. Ghosh, Bing Zhou

Tetrahedron Letters > 2013 > 54 > 27 > 3500-3502

An enantioselective aza-Michael addition of indolines to α,β-unsaturated ketones was achieved using a bifunctional cinchona alkaloid-derived chiral squaramide derivative. Various β-indolinyl ketone derivatives were obtained in good to excellent yields and with high enantioselectivity. DDQ or MnO ₂ oxidation of indoline derivatives provided convenient access to various enantioenriched N-substituted...

article

Enantioselective synthesis of spiro[cyclohexane-1,3′-indolin]-2′-ones containing multiple stereocenters via organocatalytic Michael/aldol cascade reactions

Arun K. Ghosh, Bing Zhou

Tetrahedron Letters > 2013 > 54 > 19 > 2311-2314

Organocatalytic reactions of 3-olefinic oxindoles and pentane-1,5-dial were investigated to provide access to substituted spirocyclohexane oxindoles via Michael/aldol cascade reactions. Of particular interest, we have examined the stereochemical outcome of electron withdrawing and electron-donating groups on the oxindole ring nitrogen. Interestingly, we have observed that the N-protecting group on...

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INFONA - science communication portal

Search results for: Arun K. Ghosh

Asymmetric 1,2‐Carbamoyl Rearrangement of Lithiated Chiral Oxazolidine Carbamates and Diastereoselective Synthesis of α‐Hydroxy Amides

Design, synthesis, X-ray studies, and biological evaluation of novel BACE1 inhibitors with bicyclic isoxazoline carboxamides as the P3 ligand

Design, synthesis, X-ray studies, and biological evaluation of novel macrocyclic HIV-1 protease inhibitors involving the P1′-P2′ ligands

Design of novel HIV-1 protease inhibitors incorporating isophthalamide-derived P2-P3 ligands: Synthesis, biological evaluation and X-ray structural studies of inhibitor-HIV-1 protease complex

An enantioselective enzymatic desymmetrization route to hexahydro-4H-furopyranol, a high-affinity ligand for HIV-1 protease inhibitors

Design, synthesis, and X-ray structural studies of BACE-1 inhibitors containing substituted 2-oxopiperazines as P1′-P2′ ligands

Total syntheses of both enantiomers of amphirionin 4: A chemoenzymatic based strategy for functionalized tetrahydrofurans

A fission yeast cell-based system for multidrug resistant HIV-1 proteases

Enantioselective Syntheses of (–)‐Alloyohimbane and (–)‐Yohimbane by an Efficient Enzymatic Desymmetrization Process

An enantioselective synthesis of the C3–C21 segment of the macrolide immunosuppressive agent FR252921

X-ray structure and inhibition of the feline infectious peritonitis virus 3C-like protease: Structural implications for drug design

Structure-based design, synthesis, X-ray studies, and biological evaluation of novel HIV-1 protease inhibitors containing isophthalamide-derived P2-ligands

Enantioselective synthesis of dioxatriquinane structural motifs for HIV-1 protease inhibitors using a cascade radical cyclization

Structural and biological evaluation of a novel series of benzimidazole inhibitors of Francisella tularensis enoyl-ACP reductase (FabI)

Structure-based design, synthesis and biological evaluation of novel β-secretase inhibitors containing a pyrazole or thiazole moiety as the P3 ligand

A Convergent Synthesis of Carbocyclic Sinefungin and its C‐5 Epimer

An enantioselective synthesis of a MEM-protected aetheramide A derivative

FeCl3-catalyzed tandem Prins and Friedel–Crafts cyclization: a highly diastereoselective route to polycyclic ring structures

Bifunctional cinchona alkaloid-squaramide-catalyzed highly enantioselective aza-Michael addition of indolines to α,β-unsaturated ketones

Enantioselective synthesis of spiro[cyclohexane-1,3′-indolin]-2′-ones containing multiple stereocenters via organocatalytic Michael/aldol cascade reactions

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