Stereocontrolled palladium(0)-catalyzed preparation of unsaturated azidosugars: an easy access to 2- and 4-aminoglycosides |
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Authors: | Ronaldo N de Oliveira Louis Cottier Rajendra M Srivastava |
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Institution: | a Laboratoire de Synthèse Asymétrique, UMR 5181, ESCPE Lyon, Université Claude Bernard Lyon 1, 43 boulevard du 11 Novembre 1918, 69662 Villeurbanne Cedex, France b Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, Cidade Universitaria, 50740-540 Recife, PE, Brazil |
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Abstract: | The palladium-catalyzed substitution of alkyl 4,6-di-O-acetyl-α-d-erythro-hex-2-eno-pyranosides using NaN3 as the nucleophile gave predominantly the corresponding alkyl 2-azido-2,3,4-trideoxy-α-d-threo-hex-2-enopyranosides in the presence of Pd(PPh3)4. However, alkyl 6-O-acetyl-4-azido-2,3,4-trideoxy-α-d-erythro-hex-2-enopyranosides were obtained as the major products using Pd(PPh3)4 as the catalyst in the presence of dppb as the added ligand. Conversely, alkyl 6-O-(tert-butyldimethylsilyl)-4-O-methoxycarbonyl-2,3-dideoxy-α-d-hex-2-enopyranosides gave exclusively alkyl 4-azido-6-O-(tert-butyldimethylsilyl)-2,3,4-trideoxy-α-d-erythro-hex-2-enopyranosides in the presence of Pd2(dba)3/PPh3 as the catalyst and Me3SiN3 as the nucleophile. The bis-hydroxylation followed by hydrogenation of ethyl 4-azido-2,3,4-trideoxy-α-d-erythro-hex-2-enopyranoside afforded the corresponding 4-amino-α-d-mannopyranoside, when propyl 2-azido-2,3,4-trideoxy-α-d-threo-hex-3-enopyranoside gave the 2-amino-α-d-altropyranoside under the same conditions. |
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Keywords: | Palladium catalyst Azidation Alkyl azidohexenopyranoside Amino carbohydrate |
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