| Summary: | 碩士 === 中原大學 === 化學研究所 === 97 === The nature product SJG-1 and the similar glycosphingolipids showed the nerve-growth activity. Owing to the biological activity, prompted us to study the total synthesis of these compounds.
The building unit, Neu-3 (Neu-4), was synthesized starting from sialic acid via a three-step procedure, involving esterification, per-O-acetylation, and thiophenol(ethanethiol) glycolsylation in 86% (80% )overall yield. The glucose building unit, Glc-13(Glc-15) , was prepared using glucose as starting material through a seven-step sequence, involving per-O-acetylation, orthoester reaction, deacetylation, protection of primary alcohol, benzylation, ethanethiol (thiazolinyl) glycolsylation and deprotection primary alcohol, to give the product Glc-13(Glc-15) in a overall yield of 40%( 55%). The building unit of α-hydroxyfatty acid, D-Mal-6, is made from D-(+)-malic acid through cyclohexylidene protection reaction, thioethanol glycolsylation, Wittig reaction, hydrogenation and hydrolysis to give the product, D-Mal-6, in 20%.
After glycosylation of Glc-15 with Neu-3, and Neu-4 works the glycosylation, respectively to show differen stereoselectivty (66% yeield, α:β= 3.3:1 and 70% yeield, α:β= 1.2:1).
Glycosylation of disaccharide NG-1 with phytosphingosine Lyx-9 showes excellent stereoselectivty to obtain only one β-stereoisomer in 60% yeield.
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