RESUMEN
A convenient protocol for the synthesis of 25,26,27-tribenzoyl-28-[((S)-1-diphenylphos- phanyl-propan-2-yl)oxy]-calix[4]arene via stereospecific methylation on Evans' oxazolidinone moiety was reported. According to the 13C NMR analysis of this phosphine, the calix[4]arene skeleton adopted a 1,3-alternate conformation. The latter conformation of the macrocycle and the (S)-chirality of the carbon atom bearing the methyl substituent were confirmed by a single-crystal X-ray diffraction study. After coordination of the phosphinated ligand to the dimeric [RuCl2(p-cymene)]2 organometallic precursor, the resulting arene-ruthenium complex was tested in the asymmetric reduction of acetophenone and alcohol was obtained with modest enantiomeric excess.
RESUMEN
The development of new aminoglycoside analogues to reduce the emergence of bacterial resistance has become a topic of high interest. We describe here a rapid and facile access to orthogonally protected 2-deoxystreptamine (2-DOS), a meso-diaminocyclitol known to be a pivotal component of most active aminoglycosides. Our synthetic approach started from highly protected methyl alpha-D-glucopyranoside which in turn was converted by a Ferrier rearrangement into an enantiopure polyfunctionalized cyclohexane ring. Finally, two different N-protected groups were successively introduced. The first one was inserted as an oximino benzylether followed by a diastereofacial hydride reduction, working with Me(4)NBH(OAc)(3) only in TFA at low temperature rather than in AcOH as usual. The second group was introduced by displacement of a hydroxyl group through a Mitsunobu reaction using a DPPA-DIAD-Ph(3)P system for azide transfer.
Asunto(s)
Aminoglicósidos/química , Antibacterianos/síntesis química , Ciclitoles/química , Farmacorresistencia Microbiana , Antibacterianos/química , Hexosaminas/síntesis química , Hexosaminas/química , Estructura Molecular , Oxidación-Reducción , EstereoisomerismoRESUMEN
We report a crystalline derivative of bistramide D synthesized from natural bistramide A, and its structure was determined by X-ray analysis.
Asunto(s)
Acetamidas/química , Éteres Cíclicos/síntesis química , Piranos/química , Antineoplásicos/síntesis química , Cristalografía por Rayos X , Éteres Cíclicos/química , Estructura Molecular , Compuestos de Espiro/químicaRESUMEN
A convergent stereoselective synthesis of the (3S,5R,7R,10R,11R)-C1-C13 fragment of Nystatin A(1) is reported in this paper. This fragment contains an all-syn-1,3,5-triol subunit and a syn-1,2-diol moiety. The main features of the synthesis are the enzymatic desymmetrization of a meso diol to obtain an enantiomerically pure syn-4,6-dihydroxy-2-keto-phosphonate, chiral sulfoxide chemistry to prepare an alpha-(R)-hydroxyaldehyde and 2-trimethylsilyl thiazole reagent to synthesize a syn-alpha,beta-(R,S)-dihydroxy aldehyde.