A general, transition-metal-free, highly stereoselective cross-coupling reaction between glycosyl bromides and various arylzinc reagents leading to β-arylated glycosides is reported. The stereoselectivity of the reaction is explained by invoking anchimeric assistance via a bicyclic intermediate. Stereochemical probes confirm the participation of the 2-pivaloyloxy group. Finally, this new method was applied to a short and efficient stereoselective synthesis of Dapagliflozin and Canagliflozin.
This paper describes a new reactivity of the Pd-catalyzed coupling of 2-amino-3-bromo-aromatic and heteroaromatic compounds with sulfonylhydrazones (Barluenga reaction).The new catalyst system and modulation of the electronic nature of hydrazone that were needed for successful reaction are described herein.
Diastereoselective hydrogenation of 2'-deoxy-2'-exo-methyleneuridine was carried out under homogeneous conditions using a low loading of a chiral Rh catalyst. This, coupled with improvements in the synthesis of the substrate, allowed the smooth pilot plant preparation of the title compound on >10 kg scale.
A suitable process for the preparation of kilogram quantities of a TNF-r converting enzyme (TACE) inhibitor (WAY-281418) was developed using isatin 13 as starting material and an efficient coupling step for the formation of sulfonamide 8 in a 15% overall yield. Process preparation of (+)-(1S,2R)-2-aminocyclopentane-1carboxylic acid (7, (+)-cispentacin), a chiral component for WAY-281418, was successfully scaled up via an asymmetric hydrogenation reaction. Crystallization allowed the isolation of all intermediates and the final product 9.
The carboxylic acid anion moiety has been used as a tunable directing group in the cross-coupling reaction of 2,6-dichloronicotinic acid and 2,5-dibromo-1,2,4-triazole derivatives producing selectively the 2- or 6-substituted nicotinic acids, while only the 5-substituted triazoles were obtained under a variety of conditions.
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