| A group of novel spiro alkaloids which have been proved to be with remarkable bioactivities, were isolated from Chinese medicinal herbs in recent years. As they are not rich in raw herbs, the total sythesis of these alkaloids interests many researchers. In this dissertation, two1-deoxyfructose-pyrrole derivatives are designed and synthesized as key intermediates of total synthesis of these alkaloids.Retrosynthetic analysis for these alkaloids gave rise to two fragments, pyrrole fragment and sugar fragment. D-fructose was selected as starting material. Methods of deprotection of isopropylidene and synthesis of the two1-deoxyfructose-pyrrole derivatives were studied.First, deprotection methods of isopropylidene fructopyranose derivates were tried. Using1,2:4,5-O-isopropylidene-fructopyranose as starting material, deprotection reactions catalyzed by CoCl2, acetic acid and hydrochloric acid were done. The reaction conditions, products and mechanism were discussed. Deprotection of1-deoxy-1-(4-methyl-benzensulfonyl)-2,3:4,5-O-isopropylidene-fructopyranose and1-deoxy-1-(1H-2-formyl-pyrrol-1-yl)-2,3:4,5-O-isopropylidene-fructopyranose catalyzed by DDQ under the oxidative condition was also studied.3,4,5-tri-O-acetyl-1-deoxy-1-(1H-2-formyl-pyrrol-l-yl)-β-D-fructopyranose was designed and synthesized according to the discussed route. Starting from D-fructose, aimed product was synthesized in4steps, including esterification by paratoluensulfonyl chloride, N-alkylation, formylation using Vilsmeier-Haack reaction, deprotection and esterification by acetic anhydride. The desired product was characterized by NMR and MS.3,4,5-tri-O-benzyl-l-deoxy-l-(1H-2-formyl-pyrrol-1-yl)-β-D-fructopyranose was designed and synthesized as the discussed route. Taking D-fructose as start material, aimed product was synthesized via including protection, selective deprotection, esterification and N-alkylation in an overall yield of36%. The desired product was characterized by NMR and MS. |
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