78 ガングリオシド類の全合成研究

概要

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Total synthesis of GM_3 1, GM_2 2, and GM_1 3 were described based on the synthesis strategy shown in Scheme 1. These gangliosides molecules were retrosynthesized into carbohydrate portions 4 and a ceramide 5. Compound 5 was efficiently synthesized starting from D-glucose according to "Chiron" strategy in an about 30% overall yield. Carbohydrate sequences were further simplified into a sialyllactose fragment 3 and other glycosyl donors. The glycotriaosyl structure 3 was reconstructed from a known NeuAc donor 8 and a partially protected lactose derivative 9. The glycosylation product 17, obtained in 9% yield from compounds 8 and 9, was transformed into a glycosyl donor 22 in five steps. A crucial glycosylation of 5 with 22 afforded a 37% yield of completely protected GM_3 23, which was deblocked to GM_3, identified through comparison of ^1H N.M.R. data with natural sample. Carbohydrate sequences for GM_2 and GM_1 were obtained by use of the glycosyl acceptor 17 and glycosyl donors 24 and 30, respectively. Similar technology was followed to transform compound 25 and 31 into the glycosyl donors 27 and 33 which were then reacted with a key glycosyl acceptor 5 to give protected GM_2 and GM_1, respectively. Deblocked products were identified with natural samples through comparison of ^1H N.M.R. data.
天然有機化合物討論会の論文
1986-09-09