Transformations with N-Acetylneuraminic Acid, 3. Synthesis of 7-epi-, 8-epi- and 7,8-bis-epi-N-Acetylneuraminic Acid and their Behaviour Towards the Cytidin Monophosphate Sialic Acid Synthetase

Article abstract of DOI:10.1007/BF00798282

From methyl-5-acetylamino-7,8-anhydro-4,9-O-bis-(t-butyldimethylsilyl)-3,5-dideoxy-β-D-glycero-D-galacto-2-nonulopyranosidonic acid methylester (1) the derivatives 1a and 1b were obtained by removing the 9-O-(t-butyldimethylsilyl)group with Bu4NF, followed by acetylation.Treatment of 1b with 80percent acetic acid and acetanhydride/pyridine yields the 8-epi-N-acetylneuraminic acid derivative 2a and the 7-epi-N-acetylneuraminic acid derivative 3a in a ratio 3:1 (Scheme 1).The structure elucidation of 2b was achieved by converting 2b via the 4,9-bis-O-(tBDMSi)-8-O-tosyl-derivative 2d into the epoxide 1 (Scheme 2).Using the same sequence the epoxides 4 and 5 were transformed into the N-acetylneuraminic acid derivative 6a and the 7,8-bis-epi-N-acetylneuraminic acid derivative 7a (Scheme 3).After treatment with sodium hydroxide and 0.025 m HCl and Dowex 50H(+) the 8-epi-, 7-epi- and 7,8-bis-epi-N-acetylneuraminic acid 2, 3, and 7 were obtained.These three compounds were tested with CMP-N-acetylneuraminic acid synthetase. - Keywords: Acetolysis of methyl-9-O-acetyl-5-acetylamino-7,8-anhydro-4-O-(tBDMSi)-3,5-dideoxy-β-D-(and L)-glycero-D-galacto-2-nonulosidonic acid methylester, methyl-9-O-acetyl-5-acetylamino-7,8-anhydro-4-O-(tBDMSi)-3,5-dideoxy-β-D-glycero-L-altro-2-nonulosidonic acid methylester; Configurational changes of sialic acid