Synthesis of 6-amino-6-deoxy-2,3,4,5-tetra-O-methyl-D-galactonic acid, a key precursor of a stereoregular polyamide
The title compound (17) was synthesized by two alternative sequences, starting from D-galactose diacetonide (1) and from methyl 6-O-tosyl-α-D-galac-topyranoside (9). Compound 1 was converted into the 6-bromo-6-deoxy derivative 2 or mesylated to 3. Nucleophilic substitution of the leaving group in 2...
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2001
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07328303_v20_n7-8_p689_Zaliz http://hdl.handle.net/20.500.12110/paper_07328303_v20_n7-8_p689_Zaliz |
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| Sumario: | The title compound (17) was synthesized by two alternative sequences, starting from D-galactose diacetonide (1) and from methyl 6-O-tosyl-α-D-galac-topyranoside (9). Compound 1 was converted into the 6-bromo-6-deoxy derivative 2 or mesylated to 3. Nucleophilic substitution of the leaving group in 2 and 3 by sodium azide led to the 6-azido-6-deoxy derivative 4, which on treatment with methanol under acidic conditions afforded a mixture of the corresponding methyl β-furanoside (5) and a-pyranoside (6). Methylation of the free hydroxyl groups of 5 and 6 gave the respective per-O-methyl derivatives 7 and 8. In order to maintain the size of the sugar ring during the sequence, compound 8 was alternatively prepared from 9, by acetylation, substitution by azide and per-O-methylation. Hydrolysis of the glycoside followed by oxidation and further 5-O-methylation afforded the 6-azido-6-deoxy carboxylic acid 16 which was converted into 17 (38% overall yield from 9) by hydrogenolysis of the azide function. |
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