Synthesis of the sugar moiety of TIME-EA4, a glycopeptide isolated from silkworm diapause eggs

We describe the efficient synthesis of the tetrasaccharide, 2-O-acetyl-3,4,6-tri-O-benzyl-α-d-mannopyranosyl-(1→6)-2,4-di-O-acetyl-3-O-allyl-β-d-mannopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl-(1→4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl azide, which is the protected form of the sugar unit of TIME-EA4 that is isolated from the diapausing eggs of the silkworm, Bombyx mori. The β-linked d-mannoside of the tetrasaccharide was obtained using the conventional oxidation–reduction method for inversion of the configuration at the C-2 hydroxyl group of β-d-glucoside. The reduction was effected with NaBH4 in a methanolic solution in a ratio of 98:2 in favor of the β-d-mannoside that was obtained in 87% yield.

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