Prepn. of sialoglycosyl cpds. - including cpds. useful in synthesis of ganglioside(s) and saccharide chain-antigens

摘要

Prepn. of O-glycosyl cpds. (I) of sialic acid comprises reaction of a thioglycoside (II) of sialic acid, in the presence of N-iodosuccinimide (III) and trifluoromethane-sulphonic acid (IV), with a sugar deriv. (V). Pref. (II) is methyl-(methyl-5 -acetamido-4,7,8,9- tetra-O-acetyl-3,5- dideoxy-2- thio-D-glycero-D- galacto-2-nonulopyranoside) -onate (IIa) or the corresp. phenyl-5-acetamide cpd. (IIb). (V) is (i) a galactose deriv. such as 2-(trimethylsilyl) -ethyl-6-O-benzoyl-beta- D-galactopyranoside (Va) or the corresp. 3-O-benzoyl cpd. (Vb); or (ii) a lactose deriv. such as 2-(trimethylsilyl)-ethyl-(2,6-di-O-benzyl- beta-D- galactopyranesyl)-(1-4) -2,3,6-tri-O-benzyl- beta-D-glucopyranoside (Vc). Pref. reactions involve the following component pairs: (IIa)+(Va), (IIb)+(Va), (IIa)+(Vb), (IIb)+(Vb), and (IIb)+(Vc). USE/ADVANTAGE - The prod. of the first two above reactions, (A), is an intermediate in the synthesis of the saccharide chain-antigen 2-3 Sialyl LC4. The prod. of reaction between (IIb) and (Vc) is an intermediate in the synthesis of gangliosides GM3, GM2 and GM1. The process shows high regio- and stereoselectivity, is economical, and gives good yields. SE = 2-(trimethylsilyl)-ethyl