- Northampton, UK
Koushik Das Sarma
University of Essex, Business and Management, Department Member
- Coventry University (coventry.ac.uk), Business Management, Faculty MemberShoolini University, Pharmaceutical Sciences, Adjunctadd
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full... more
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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ABSTRACT
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The influence of aqueous reaction media on organic reactions is a topic of long-standing interest, particularly as it affects the rate or selectivity of synthetic reactions. Sometimes such reactions appear homogeneous, typically in dilute... more
The influence of aqueous reaction media on organic reactions is a topic of long-standing interest, particularly as it affects the rate or selectivity of synthetic reactions. Sometimes such reactions appear homogeneous, typically in dilute solution, whereas others are obviously heterogeneous, typically in concentrated solution that is more characteristic of a preparative synthetic reaction. The latter situation has been termed "on water." Here, it is demonstrated that the rates of heterogeneous ene reactions, Passerini reactions, and Ugi reactions in pure water and in aqueous solutions are dependent on the mixing method and reactant polarity, consistent with the involvement of hydrophobic interactions in their acceleration.
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Amino Acid Esters and Amides for Reductive Amination of Mucochloric Acid: Synthesis of Novel γ-Lactams, Short Peptides and Antiseizure Agent Levetiracetam (Keppra®)-Das Sarma-2006-European Journal of Organic Chemistry-Wiley Online Library
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Rings are constructed when using a reactant incorporating two of the four functional groups required in the Ugi reaction. For example, use of β-amino acids in an Ugi four-component condensation with isonitriles and carbonyl compounds... more
Rings are constructed when using a reactant incorporating two of the four functional groups required in the Ugi reaction. For example, use of β-amino acids in an Ugi four-component condensation with isonitriles and carbonyl compounds produces β-lactams. [6] While keto acids ...
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4. General procedure: All the reactions were done under argon atmosphere in deoxygenated water. (a) Water soluble substrates: A mixture of 3-bromobenzoic acid (25 mM), NaHCO 3 (40 mM) and AIBN (0.30 equiv.) in water was stirred for 15... more
4. General procedure: All the reactions were done under argon atmosphere in deoxygenated water. (a) Water soluble substrates: A mixture of 3-bromobenzoic acid (25 mM), NaHCO 3 (40 mM) and AIBN (0.30 equiv.) in water was stirred for 15 min. TBTH (3.1 equiv.) was added ...
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A modified trypan blue dye exclusion assay was developed usingNi(2+) or Co(2+) salts to determine the viability ofprimary and transformed cells. When the cells were preincubatedwith NiSO(4) or CoCl(2) followed by trypan blue assay,... more
A modified trypan blue dye exclusion assay was developed usingNi(2+) or Co(2+) salts to determine the viability ofprimary and transformed cells. When the cells were preincubatedwith NiSO(4) or CoCl(2) followed by trypan blue assay, thecontrast between stained and unstained cells was significantlyincreased as compared to the conventional trypan blue dyeexclusion assay.
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ABSTRACT Oxygenated five-membered ring compounds are more widespread in nature than the corresponding aza-analogues due to their more interesting biological activity. In our earlier studies, we have reported a simple methodology to... more
ABSTRACT Oxygenated five-membered ring compounds are more widespread in nature than the corresponding aza-analogues due to their more interesting biological activity. In our earlier studies, we have reported a simple methodology to synthesize novel synthons like 5-(1′-hydroxy)-γ-butenolide and 5-(1′-hydroxy)-γ-butyrolactam through the direct vinylogous aldol addition reaction. The observed diastereoselectivities for γ-butyrolactones and γ-butyrolactams were not understood in that report. We have reported herein a detailed computational study to understand the observed diastereoselectivity of α,β-dichloro-γ-butenolides and α,β-dichloro-γ-butyrolactams. The transition state calculations performed with B3LYP/cc-pVDZ level of theory to examine the diastereoselectivity of α,β-dichloro-γ-butenolides and α,β-dichloro-γ-butyrolactams have been found to be in good agreement with the observed experimental results. The origin of selectivity is examined by an activation strain model and molecular electrostatic potential (MESP) surfaces. The distortion energies calculated using the activation strain model revealed the origin of diastereoselectivities for butenolides and butyrolactams. The reversal in stereochemical outcome of α,β-dichloro-γ-butenolides and α,β-dichloro-γ-butyrolactams is due to the presence of a large substituent at the nitrogen center of the γ-butyrolactams. We have further revealed the enhanced diastereoselectivity of these butenolides while reacting with the aromatic aldehydes bearing ortho substituents. The generated molecular electrostatic potential (MESP) surfaces have shown an additional Vmin of value = −115.0 kcal mol−1 responsible for enhanced diastereoselectivity with ortho-substituted benzaldehydes as compared to unsubstituted benzaldehyde. The difference in transition state distortion energies of syn and anti aldol products are found to correlate with their corresponding differences in activation energies.
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4. General procedure: All the reactions were done under argon atmosphere in deoxygenated water. (a) Water soluble substrates: A mixture of 3-bromobenzoic acid (25 mM), NaHCO 3 (40 mM) and AIBN (0.30 equiv.) in water was stirred for 15... more
4. General procedure: All the reactions were done under argon atmosphere in deoxygenated water. (a) Water soluble substrates: A mixture of 3-bromobenzoic acid (25 mM), NaHCO 3 (40 mM) and AIBN (0.30 equiv.) in water was stirred for 15 min. TBTH (3.1 equiv.) was added ...
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In vitro ADME characterization of the lead compound 1 identified for visceral leishmaniasis was undertaken and further structural analogs were synthesized for antileishmanial screening. Compound 1 was highly permeable in intestinal PAMPA... more
In vitro ADME characterization of the lead compound 1 identified for visceral leishmaniasis was undertaken and further structural analogs were synthesized for antileishmanial screening. Compound 1 was highly permeable in intestinal PAMPA model (31 × 10(-6)cm/s) and was moderately bound to mouse and human plasma proteins (% bound 85-95%), its blood to plasma concentration ratio was less than 1, but the compound was unstable in blood. Compound 1 was found to have no CYP450 liability with CYP2C9, 2C19, 2D6 and 3A4. It showed inhibition with CYP1A2 with an IC50 value of 0.50 μM. Analogs of 1 were synthesized and subsequently characterized for in vitro activity against the intracellular form of Leishmania donovani. Resulting quinolines were found to have similar efficacy as 1 against the parasite. Compounds 8b and 8f were found to be the most active with IC50 values of 0.84 μM and 0.17 μM, respectively compared to 0.22 μM for compound 1. Of all the analogs tested, 8d was stable in hamster, mouse and human liver microsomes but lost the efficacy with an IC50 of 6.42 μM. Based on the in vitro efficacy and DMPK profile, compounds 8b and 8f seem the best candidates to be screened in further assays.
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SAR studies were performed on a series of 2-arylamido-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxamide derivatives as cannabinoid receptor agonists. Starting from a HTS hit both potency and selectivity could be improved. Modifications to... more
SAR studies were performed on a series of 2-arylamido-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxamide derivatives as cannabinoid receptor agonists. Starting from a HTS hit both potency and selectivity could be improved. Modifications to the thiophene fusion and C-3 amides were studied. A representative compound 3t produced analgesia when dosed orally in inflammatory pain models of writhing and carrageenan-induced allodynia.
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full... more
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
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A simple methodology utilizing mucochloric acid anddifferent α- and β-amino acid esters, amides and shortpeptides for the synthesis of novel γ-lactam and γ-lactam-based short peptides was developed. The synthesis of an antiseizure agent,... more
A simple methodology utilizing mucochloric acid anddifferent α- and β-amino acid esters, amides and shortpeptides for the synthesis of novel γ-lactam and γ-lactam-based short peptides was developed. The synthesis of an antiseizure agent, Levetiracetam (Keppra®) was demonstrated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
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Rings are constructed when using a reactant incorporating two of the four functional groups required in the Ugi reaction. For example, use of β-amino acids in an Ugi four-component condensation with isonitriles and carbonyl compounds... more
Rings are constructed when using a reactant incorporating two of the four functional groups required in the Ugi reaction. For example, use of β-amino acids in an Ugi four-component condensation with isonitriles and carbonyl compounds produces β-lactams. [6] While keto acids ...
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The influence of aqueous reaction media on organic reactions is a topic of long-standing interest, particularly as it affects the rate or selectivity of synthetic reactions. Sometimes such reactions appear homogeneous, typically in dilute... more
The influence of aqueous reaction media on organic reactions is a topic of long-standing interest, particularly as it affects the rate or selectivity of synthetic reactions. Sometimes such reactions appear homogeneous, typically in dilute solution, whereas others are obviously heterogeneous, typically in concentrated solution that is more characteristic of a preparative synthetic reaction. The latter situation has been termed "on water." Here, it is demonstrated that the rates of heterogeneous ene reactions, Passerini reactions, and Ugi reactions in pure water and in aqueous solutions are dependent on the mixing method and reactant polarity, consistent with the involvement of hydrophobic interactions in their acceleration.
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For Abstract see ChemInform Abstract in Full Text.