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Regioselective aectylations of sialic acid α‐ketosides
Author(s) -
Reinhard Bernd,
Faillard Hans
Publication year - 1994
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199419940214
Subject(s) - acetylation , chemistry , sialic acid , dimethylacetamide , acetal , catalysis , derivative (finance) , organic chemistry , biochemistry , solvent , financial economics , economics , gene
Various partially acetylated sialic acid α‐ketosides were obtained without expensive protecting group techniques by using trimethyl orthoacetate or dimethylacetamide dimethyl acetal as acetylating agents or by performing a partial Zemplén de‐ O ‐acetylation. Using trimethyl orthoacetate as acetylating agents we synthesized 9‐ O ‐acetylated, 8‐ O ‐acetylated, and 8,9‐di‐ O ‐acetylated sialic acid α‐ketoside benzyl ester derivatives. The acetylation with dimethylacetamide dimethyl acetal yielded 9‐ O ‐acetylated, 8‐ O ‐acetylated, 4, 9‐di‐ O ‐acetylated, 8,9‐di‐ O ‐acetylated, and 4,8,9‐tri‐ O ‐acetylated sialic acid α‐ketoside benzyl ester derivatives. The partial Zemplén de‐ O ‐acetylation permitted the synthesis of 7,8,9‐tri‐ O ‐acetylated sialic acid α‐ketoside benzyl ester derivatives. After catalytic hydrogenation the 8‐ O ‐acetylated derivatives 2e and 3d were not stable and were completely converted into the 9‐ O ‐acetylated sialic acid α‐thioketoside 2k . The N ‐acetyl‐8,9‐di‐ O ‐acetylneuraminic acid α‐aminophenylthioketoside 21 showed a migration of the acetyl group from position 8 to position 7 in polar solvents, yielding a mixture of the 8,9‐di‐ O ‐ and the 7 , 9‐di‐ O ‐acetylated derivatives 21 and 2m in a molar ratio of approximately 1:1. The 7 , 9‐di‐ O ‐acetylated derivative 2m could be separated and was completely stable in methanol. Using the isopropylidene protecting group we could also prepare the 4‐ O ‐acetylated sialic acid α‐thioketoside 2o . Treatment of the 9‐ O ‐acetylated derivative 2k with fluorescein isothiocyanate gave the fluorescent derivative 5 .