Synthesis Of The Aglycone Of Linckoside B And Antibacterial Oligorhamnoside Derivatives

This paper involves the construction of hydroxyl and double bond, which lie onthe aglycone of linckoside B. This plays a key role in the total synthesis of linckosideB. In addition, the paper also involves the design and synthesis of antimicrobialoligorhamnoside cleistrioside-5derivatives, in order to simplify the structure to gainthe drug candidates which possess better pharmacological activity.1. Synthesis of the aglycone of linckoside BMarine steroid glycosides linckosides, were isolated from the Okinawan starfishLinckia laevigata, which represent an important class of polyhydroxy steroidglycosides. These compounds are not only potent inducers of neurite outgrowth onPC12cells but also significant enhancers of nerve growth factor (NGF) to induce theneurite outgrowth. These new small-molecule skeleton is very promising for thetreatment of various neurodegenerative diseases. Accordingly it is essential tosynthesize the aglycone of linckoside B which possesses the highest activity and thereis far-reaching significance for the study of such molecules. This paper completed theconstruction of6-β-OH,15--OH and the double bond, while attempted to build8-β-OH of the steroid.2. Synthesis of antimicrobial oligorhamnoside derivativesThe oligosaccharides units of glycoconjugates have an important influence ontheir biological activity. At present, a great interest in the synthesis of glycoconjugatesto elucidate the associations of oligosaccharides with disease mechanisms is raising.Cleistrioside-5was obtained from Cleistopholis patens, which is a small genuswith only three or four species, all in tropical Africa, by Hu’s group. It was found topossess significant in vitro antibacterial activity against the Gram-positive bacteria.According to Dr. Zhang’s report, one dis-oligorhamnoside the sugar chain length of two and three seemed to have no influence on the antibacterial activities because bothcleistrioside-5and the compound3-1had the same antibacterial profiles against thepanel of bacteria. In view of this, two series of rhamnoside derivatives are designedand synthesized.