Syed Tasadaque Ali Shah

A novel method for the syntheses of symmetrical disulfides using CsF–Celite as a solid base

Abstract The oxidative coupling of aliphatic, aromatic and heteroaromatic thiols to disulfides using cesium fluoride–Celite is described. CsF–Celite provides an efficient, convenient and practical method for the syntheses of symmetrical disulfides.

An alternative approach towards the syntheses of thioethers and thioesters using CsF–Celite in acetonitrile

Abstract It has been found that syntheses of thioethers and thioesters of aliphatic, aromatic and heterocyclic compounds, bearing thiol groups, can be accomplished with alkyl, acyl, benzyl or benzoyl halides in acetonitrile and cesium fluoride–Celite. In this manner, compounds like ethanethiol, 1-pentanethiol, thiophenol, 4-methoxythiophenol, 4-nitrothiophenol, and 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, and 2-mercapto-2-thiazoline can be successfully alkylated, acylated, benzylated or benzoylated. This procedure is convenient, efficient and practical for the preparation of thioethers and thioesters.

An Efficient Method for the Synthesis of Peptide Aldehyde Libraries Employed in the Discovery of Reversible SARS Coronavirus Main Protease (SARS-CoV Mpro) Inhibitors

A method for the parallel solid‐phase synthesis of peptide aldehydes has been developed. Protected amino acid aldehydes obtained by the racemization‐free oxidation of amino alcohols with Dess–Martin periodinane were immobilized on threonyl resins as oxazolidines. Following Boc protection of the ring nitrogen to yield the N‐protected oxazolidine linker, peptide synthesis was performed efficiently on this resin. A peptide aldehyde library was designed for targeting the SARS coronavirus main protease, SARS‐CoV Mpro(also known as 3CLpro), on the basis of three different reported binding modes and supported by virtual screening. A set of 25 peptide aldehydes was prepared by this method and investigated in inhibition assays against SARS‐CoV Mpro. Several potent inhibitors were found with IC50 values in the low micromolar range. An IC50 of 7.5 μM was found for AcNSTSQ‐H and AcESTLQ‐H. Interestingly, the most potent inhibitors seem to bind to SARS‐CoV Mpro in a noncanonical binding mode.

An efficient approach towards syntheses of ethers and esters using CsF-Celite as a solid base

Abstract The coupling reactions of a number of alcohols and phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride–Celite are described. It has been found that CsF–Celite combinations provide an efficient, convenient and practical method for syntheses of both, ethers and esters.

Synthesis and Bioactivities of Naturally Occurring Anthraquinones: Isochrysophanol, Isozyganein, ω-Hydroxyisochrysophanol and Morindaparvin

Isochrysophanol, isozyganein, ω-hydroxyisochrysophanol, and morindaparvin are naturally occurring substituted anthraquinones. We report the synthesis of these compounds as well as selected biological activities.

Isolation and Structure Elucidation of Two New Xanthones from Gentiana azurium Bunge (Fam. Gentianaceae)

Abstract Two new natural xanthones, 1,3,5-trihydroxy-8-methoxyxanthone (1) and 3,5-dihydroxy-8- methoxy-1-O-β-D-glucopyranosyl xanthone (2) were isolated along with two known xanthones from Gentiana azurium Bunge (Fam. Gentianaceae). Their structures were determined on the basis of their spectral data.

Syntheses and Evaluation of the Analgesic Activity of Some 4-Acetyl- 4-phenylpiperidine and 4-Hydroxy-4-phenylpiperidine Derivatives

Synthesis and analgesic activity of 4-phenylpiperidine derivatives is a topic of high actuality. A s part of a programme towards obtaining new potential analgesics, ten derivatives of 4- acetyl-4-phenylpiperidine and ten derivatives of 4-hydroxy-4-phenylpiperidine were synthesised and characterized through spectroscopic techniques. All derivatives along with the parent compounds were evaluated for analgesic activity in the acetic acid-induced writhing assay and tail-flick test in mice. All derivatives of 4-acetyl-4-phenylpiperidine except one com pound exhibited more or less protection against mice writhing, whereas all the compounds proved to be inactive in the tail-flick test at doses of 50 and 100 mg/kg body weight.

Regioselective Conversion of Anhydro Sugars into Halohydrins and X-Ray Study

A rapid, easy, regio- and stereoselective synthesis of 3-halo-3-deoxy sugars using titanium tetrahalides is described. To fully confirm the stereochemistry of the synthetic products, the X-ray structure of benzyl 3-chloro-3-deoxy-β -L-xylopyranoside was determined

Sodium hydride/hexamethylphosphoric triamide: a new and efficient reagent towards the synthesis of protected 1,2- and 5,6-enopyranosides

A new method for the elimination of hydrogen halides and p-toluenesulfonic acid from sugar moieties using sodium hydride (NaH) in hexamethylphosphoric triamide (HMPA) at room temperature is reported. NaH/HMPA has several advantages compared to NaH/DMF: elimination products are produced in high yields even from sterically hindered starting materials, and not only from halides, but also tosylates.