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Synthesis of Chiral Ligands and Their Applications in Combinatorial Asymmetric Catalysis

Thesis Info

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Author

Zaman, Tariq

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2721/1/2898S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727481229

Similar


Enhanced effectiveness of pharmaceuticals and agrochemicals is the most sought-after attribute in the field of enantioselective synthesis of chiral molecules where single enantiomer (R or S) is required, for which asymmetric catalysis is an attractive way. The synthesis of enantiomerically pure compounds in traditional way is difficult, costly and time-consuming process involving the running of long columns which create a lot of waste that causes water pollution. The selectivity of products are equally depends upon the catalyst and conditions of the reaction which makes the task harder for selecting and finding new catalytic system. Present work deals with the development of six families of chiral ligands libraries for rapid recognition of the best system, by using combinatorial chemistry, during hydrogenation of ketones, a starting material and as intermediate in a number of pharmaceutical processes. The ligands were both generated in situ and in pure form for the comparison of results and were obtained by simple condensation, providing one of the starting materials being chiral. Six families namely; bisimine, diamine, aminal, imine, iminophosphine and oxazoline were synthesized and tested in presence of Zn(II), Rh(I) and Rh(III) by using polymethylhydrosiloxane (PMHS), diphenylsilane and formic acid/sodium formate as hydrogen donor species for transfer hydrogenation during synthesis of selective chiral alcohols from achiral acetophenone. Overall 1566 catalytic systems were developed and subsequently tested and the yield and enantiomeric excesses were found by using 1H NMR and chiral High Performance Liquid Chromatography (HPLC) respectively with more than 90% ee and 99% conversion as the best result for imine and aminal ligands. It has been proven that ligands synthesized in-situ gave comparable and almost same results to purified version with best reproducibility.
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اسلم ملک

اسلم ملک
اسلم ملک (۱۹۳۱ء پ) سیالکوٹ کے محلہ دھارو وال میں پیدا ہوئے ۔(۹۹۸) نثر نگاری ان کی پہچان ہے لیکن اظہار کے لیے انھوں نے شاعری کا لطیف پیرایہ بھی استعمال کیا ہے۔ اسلم ملک نے بچوں کے ادب کو زیادہ اہمیت دی ہے۔ اس لیے ان کی شاعری کا بڑا حصہ بچوں کی شاعری پر محیط ہے۔اسلم ملک نے حمد سے نعت ،غزل نظم اور ہائیکو جیسی اصناف میں طبع آزمائی کی ہے۔ اسلم ملک کا شعری مجموعہ ’’خواب اور خوشبو‘‘شائع ہو چکاہے۔ تصوف اور عشقِ حقیقی اسلم ملک کی شاعری کا ایک بڑا موضوع ہے۔ اسلم ملک کے نزدیک صرف خدائے رحیم و کریم ،تعظیم ،عظمت اور تمہیدو ستائش کا حقدار ہے۔ لالہ و گل میں اس کی خوشبو ہے۔ اور سورج چاند ستاروں کی روشنی بھی اسی سے ہے کیونکہ وہ نور اور نور کا منبع ہے۔ کچھ اشعار ملاحظہ ہوں:
لالہ و گل میں جو خوشبو ہے فقط تری ہے
چاند ستاروں کی چمک میں بھی ہے فیضان تیرا
گیت تیرے ہی سناتے ہیں پرندے سارے
بزمِ قیمتی کا ہر اک فرد ثنا خواں تیرا (۹۹۹)

تو خالق و مالک ارض و سما

سبحان اللہ ، سبحان اللہ

تو داتا مرے دل میں بسا

سبحان اللہ ، سبحان اللہ

خلقت ساری ہے کنبہ ترا

سبحان اللہ ، سبحان اللہ

تو افضل و اکمل سب سے بڑا

سبحان اللہ ، سبحان اللہ
(۱۰۰۰)

شہ دو جہاں کا کرم چاہتا ہوں

سفر اپنا سوئے حرم چاہتا ہوں

دیا ان کا روشن رہے طاقِ دل پر

میں الفت میں ان کا بھرم چاہتا ہوں
(۱۰۰۱)

پاکستان کا مسئلہ نمبر 1 کرپشن: اسباب اور خاتمہ تعلیمات نبویﷺ کے آئینے میں

The word corruption is very comprehensive. It is  the  synonym   of   bribery, demoralization, sinfulness, wickedness,   impurity, dishonesty, fraud, falsehood, embezzlement, illegal  and  criminal,   etc.  Currently  in  pakistan government & private  sectors,   high rank  government  employees,   bureaucracy and political institutions,   are  involved  in  different  kinds  of  corruption.  Consequently, the economy of the courntry has  been effected  extremly.  Therefore,   there  is  no peace in the counrtry. CALVIN COOLIDGE said in his speech, in 1923: "Economy is always a guarantee of peace". (1) In this  research article  it  would be   searched that  how the  corruption  in the country   could   be   eradicated,    in the  light of  Islamic teachings.  So that the economy of the the country can make progress smoothly and easily.

Selective Degradation and Oxidation of Hydroxyethyl Starch for Immobilization of Some Antidiabetic Drugs

The low solubility and permeability of drugs, in general, leads to unsatisfactory pharmacokinetics profile of drugs. Polymer conjugation has attracted increasing interest in pharmaceutical industry for delivering such low molecular weight (Mw) drugs as well as some complex compounds. The objective of this work was to find a method to overcome the solubility and permeability problems using the conjugation strategy. In this regard, hydroxyethyl starch (HES), a highly biocompatible semi-synthetic biopolymer, was used as a drug carrier. N- Arylsulfonylbenzimidazolones were selected as antidiabetic compounds of choice for coupling with HES. The experiments established the viability of a covalent coupling between polymer and N-arylsulfonylbenzimidazoles using a suitable coupling strategy. As a requirement for the desired coupled products, HES must have Mw that is suitable for drug delivery and excretion through the kidney. Therefore, HES needs to undergo a selective degradation. In the present study, two different methods for hydrolysis, i.e. acidic and enzymatic, were used for selective degradation of HES. It was found that the enzymatic hydrolysis method is superior to acidic hydrolysis. The enzymatic method was used to obtain HES of Mw as low as ≈ 10,000 g/mol. The selectively degraded HES was oxidized to generate carboxylic acid groups at the chain ends to serve as a coupling site for N-arylsulfonylbenzimidazolones, the selected antidiabetic compounds. For oxidation of HES, potassium permanganate and sodium oxychloride were tried as oxidizing agents. The sodium oxychloride method was found advantageous over permanganate method. The degraded and oxidized products were characterized using GPC, IR and NMR techniques. N-Arylsulfonylbenzimidazolones were synthesized using a multistep sequence to serve as antidiabetic compounds. The structures of all the synthesized arylsulfonylbenzimidazolne products and intermediates were established using spectroscopic techniques and the purity ascertained by elemental analysis. The synthesized arylsulfonylbenzimidazolnes were coupled to oxidized HES of molecular weights 17,490 g/mol and 10,067 g/mol by creating an amide linkage between the two units. iiThe coupled products were characterized using GPC, IR, 1 H NMR and 13 C NMR spectroscopy. The coupled products were screened for their antidiabetic potential on male albino rats of the Sprague–Dawley albino family at a dose of 20 mg and 40 mg per Kg body weight of the rats. It was observed that all the synthesized compounds were highly active. 2,3-Dihydro-3-(4- nitrobenzensulfonyl)-2-oxo-1H-benzimidazole (63) was found most potent with a 54 % reduction in blood glucose level of the rats as compared to 41 % reduction produced by tolbutamide and 38 % by glucophage. The coupling of these antidiabetic compounds with oxidized HES resulted in an increase of the hypoglycemic activity of all the compounds. The activity of compound 63 on coupling to HES 10,067 increased to 67 % reduction in blood glucose level.