Synthesis of fully protected α-l-fucopyranosyl-(1→2)-β-d-galactopyranosides with a single free hydroxy group at position 2′, 3′ or 4′ using O-(2-naphthyl)methyl (NAP) ether as a temporary protecting group
摘要:
Perbenzylated methyl alpha-L-fucopyranosyl-(1-->2)-beta-D-galactopyranosides having a single free OH group at position C-2'. C-3' or C-4' have been synthesized. Methyl 3,4,6-tri-O-benzyl-beta-D-galactopyranoside was glyco-sylated either with phenyl 3,4-di-O-benzyl-2-O-(2-naphthyl)-methyl-, phenyl 2,4-di-O-benzyl-3-O-(2-naphthyl)methyl- or phenyl 2,3-di-O-benzyl-4-O-(2-naphthyl)methyl-1-thio-beta-L-fucopyranoside. The 2-ONAP ether functioned well as a non-participating group. The yields of the glycosylation reactions, promoted by NIS/TfOH, were above 80% and the stereoselectivity was 8:1 to 10:1 in favour of the alpha-anomers. The 2-ONAP ether was obtained by (2-naphthyl)methylation, the 3-ONAP and the 4-ONAP ethers were prepared either by hydrogenolysis of the 3,4-O-(2-naphthyl)methylene acetals of beta-L-fucopyranoside or by tin acetal-mediated alkylations. The latter procedure afforded higher yields. The ONAP ethers from the disaccharides were removed by oxidative cleavage with DDQ. (C) 2004 Elsevier Ltd. All rights reserved.
Synthesis of fully protected α-l-fucopyranosyl-(1→2)-β-d-galactopyranosides with a single free hydroxy group at position 2′, 3′ or 4′ using O-(2-naphthyl)methyl (NAP) ether as a temporary protecting group
摘要:
Perbenzylated methyl alpha-L-fucopyranosyl-(1-->2)-beta-D-galactopyranosides having a single free OH group at position C-2'. C-3' or C-4' have been synthesized. Methyl 3,4,6-tri-O-benzyl-beta-D-galactopyranoside was glyco-sylated either with phenyl 3,4-di-O-benzyl-2-O-(2-naphthyl)-methyl-, phenyl 2,4-di-O-benzyl-3-O-(2-naphthyl)methyl- or phenyl 2,3-di-O-benzyl-4-O-(2-naphthyl)methyl-1-thio-beta-L-fucopyranoside. The 2-ONAP ether functioned well as a non-participating group. The yields of the glycosylation reactions, promoted by NIS/TfOH, were above 80% and the stereoselectivity was 8:1 to 10:1 in favour of the alpha-anomers. The 2-ONAP ether was obtained by (2-naphthyl)methylation, the 3-ONAP and the 4-ONAP ethers were prepared either by hydrogenolysis of the 3,4-O-(2-naphthyl)methylene acetals of beta-L-fucopyranoside or by tin acetal-mediated alkylations. The latter procedure afforded higher yields. The ONAP ethers from the disaccharides were removed by oxidative cleavage with DDQ. (C) 2004 Elsevier Ltd. All rights reserved.