نتایج جستجو برای: stereoselective
تعداد نتایج: 4707 فیلتر نتایج به سال:
Stereoselective Reduction of Imines with Trichlorosilane Using Solid-Supported Chiral Picolinamides.
The stereoselective reduction of imines with trichlorosilane catalyzed by chiral Lewis bases is a well-established procedure for the synthesis of enantio-enriched amines. Five supported cinchona-based picolinamides have been prepared and their activity tested in a model reaction. The comparison of different supporting materials revealed that polystyrene gave better results than silica in terms ...
Starting from succinic anhydride and 2-methylanisole, a chemoenzymatic collective formal/total synthesis of several optically active tetrahydronaphthalene based bioactive natural products has been presented via advanced level common precursors; the natural product and antipode (-)/(+)-aristelegone B. Regioselective benzylic oxidations, stereoselective introduction of hydroxyl groups at the α-po...
A convergent total synthesis of ouabagenin, an aglycon of cardenolide glycoside ouabain, was achieved by assembly of the AB-ring, D-ring and butenolide moieties. The multiply oxygenated cis-decalin structure of the AB-ring was constructed from (R)-perillaldehyde through the Diels-Alder reaction and sequential oxidations. The intermolecular acetal formation of the AB-ring and D-ring fragments, a...
A convergent total synthesis of ouabagenin, an aglycon of cardenolide glycoside ouabain, was achieved by assembly of the AB-ring, D-ring and butenolide moieties. The multiply oxygenated cis-decalin structure of the AB-ring was constructed from (R)-perillaldehyde through the Diels–Alder reaction and sequential oxidations. The intermolecular acetal formation of the AB-ring and D-ring fragments, a...
The combination of experimental with theoretical CD spectroscopy allows the observation of stereoselective helical folding in a self-assembled capsule.
A practical approach has been developed to convert glucals and rhamnals into disaccharides or glycoconjugates with high a-selectivity and yields (77–97%) using a trans-fused cyclic 3,4-O-disiloxane protecting group and TsOH·H2O (1 mol%) as a catalyst. Control of the anomeric selectivity arises from conformational locking of the intermediate oxacarbenium cation. Glucals outperform rhamnals becau...
The efficient cyclic aminal formation leads to the stereoselective synthesis of corresponding [2+2] macrocycles, for which dynamic covalent nature bond can be controlled under specific conditions.
We have developed a general strategy for the synthesis of 2,5-syn disubstituted pyrrolidines that is based on the multi-faceted reactivity of the sulfone moiety and a 5-endo-trig cyclisation. This methodology was applied to the synthesis of indolizidine alkaloid monomorine I. Two factors were key to the success of this endeavour; the first was the choice of nitrogen protecting group whilst the ...
A stereoselective synthesis of the monodeuterated methyleneaziridine shown allowed stereochemical course formal SNV-mode ring-opening with copper-based organometallics to be assigned.
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