نتایج جستجو برای: stereoselectively
تعداد نتایج: 274 فیلتر نتایج به سال:
acebutolol (ac) is a chiral b-adrenergic blocking drug, which is useful clinically as the racemate in treating hypertension and is metabolized to an equipotent chiral metabolite, diacetolol (dc). in this paper we report a case of a 32 year old woman who was receiving ac during her pregnancy and lactating time for management of hypertension. the maternal plasma level and breast milk as well as c...
Methylphenidate is an important stimulant prescribed to treat attention-deficit hyperactivity disorder. It has two chiral centers, but most current commercial formulations consist of the racemic mixture of the threo pair of methylphenidate isomers (d-, l-threo-methylphenidate). The d-isomer is the pharmacologically active component. Numerous studies reported that oral administration of the meth...
Most of polypeptides containing α,β-dehydroamino acids have important biological activity, so exploration of synthetic method has practical significance. In this paper, dipeptides were prepared from l-threonine by protecting of c-terminal allyl acetate, and condensing reaction with a series of N-Boc amino acid. Then, treatment of dipeptides obtained with DMAP, (Boc)2O and tetramethylguanidine i...
The sequential 1,4-elimination reaction of (E)-4-alkoxy-2-butenyl benzoates and [1,2]-Wittig rearrangement gave (2Z,4E)-2,4-pentadien-1-ols stereoselectively. Z-Selective formation of intermediary vinyl ethers, whose stereochemistry was well elucidated by the "syn-effect", was achieved by treatment of the 2-butenyl benzoates with KOH in the presence of Pd catalyst. The subsequent [1,2]-Wittg re...
Mycothiol is found in Gram-positive bacteria, where it helps in maintaining a reducing intracellular environment and it plays an important role in protecting the cell from toxic chemicals. The inhibition of the mycothiol biosynthesis is considered as a treatment for tuberculosis. Mycothiol contains an α-aminoglycoside, which is difficult to prepare stereoselectively by a conventional glycosylat...
By the use of an N-heterocyclic carbene copper(I) complex as a catalyst, the boracarboxylation of various alkynes (e.g., diaryl alkynes, aryl/alkyl alkynes, and phenylacetylene) with a diborane compound and carbon dioxide has been achieved for the first time, affording the α,β-unsaturated β-boralactone derivatives regio- and stereoselectively via a borylcupration/carboxylation cascade. Some imp...
A polymer-supported Hantzsch 1,4-dihydropyridine ester was observed to be a useful selective reducing agent for the reduction of ketimines and electron-withdrawing conjugated olefins. The rate of the reduction of electron-withdrawing conjugated olefins is dependent on the nature of the conjugated substituents and could be enhanced by microwave irradiation. The reduction of (Z)-a-cyano-bbromomet...
Functionalized vinyl pinacol boronates suitable for Suzuki cross-coupling reactions are synthesized using ruthenium-catalyzed olefin cross-metathesis of 1-propenyl pinacol boronate and various alkenes, including functionalized and 1,1-disubstituted alkenes. The resultant boronate cross products are stereoselectively transformed into predominantly Z-vinyl bromides and E-vinyl iodides. The vinyl ...
A series of glycosyl hemiacetal derivatives have been transformed into thioglycosides and glycosyl thiols in a one-pot two-step reaction sequence mediated by Appel reagent (carbon tetrabromide and triphenylphosphine). 1,2-trans-Thioglycosides and β-glycosyl thiol derivatives were stereoselectively formed by the reaction of the in situ generated glycosyl bromides with thiols and sodium carbonotr...
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