Use Of Steroidal Saponins Yuan Synthesis Of Biodegradable Waste (r) - 4 - Methyl - 2 - Diazo - 5 - Valeric Acid Dimethyl Benzyl Oxygen Radicals Such As Chiral Synthesis Research

Asymmetric Synthesis has become one of the most important parts of organic synthesis. Using the nature chiral source with low cost and easy obtained to introduce asymmetry factor has many advantage. The clean degradation of steroidal sapogenins with hydrogen peroxide via a novel method developed by our group not only can reduce the environmental pollution but also obtain some chiral moleculars. For furtherly rational utilization of steroidal sapogenins, we wish converted such chiral moleculars into some more valuable chiral reagents.This dissertation is concerned on syntheses of some valuable chiral synthons using potassium (2R,4R)-2,5-dihydroxy-4-methylpentanoate obtained by degradation of steroidal sapogenins as the starting material. It mainly includes the following parts:1. Using potassium (3R,5R)-3-hydroxy-5-methyl-tetrahydropyran-2-one2-2as the starting material, it was converted into (R)-methyl5-(benzyloxy)-4-methyl-2-oxopentanoate2-4according to a known method. And then compound2-4reacted with p-methylbenzenesulfonohydrazide to generate the corresponding hydrazone. Decomposation of hydrazone with K2CO3generated a valuable chiral synthon (R)-methyl5-(benzyloxy)-2-diazo-4-methylpentanoate2-7.2. The reaction of (R)-methyl5-(benzyloxy)-2-diazo-4-methylpentanoate2-7with Rh2(OAc)4was explored in detail. A chiral synthon (R, Z)-methyl5-(benzyloxy)-4-methylpent-2-enoate3-2was obtained in72%yield.3. Using one-pot way,(R)-methyl5-(benzyloxy)-4-methyl-2-oxopentanoate2-4reacted with LDA and isopentyl nitrite to give an important chiral synthon4-1which had1,3-double functional groups and two less carbon atoms than the starting material in25%yield.4. Using potassium (2R,4R)-2,5-dihydroxy-4-methylpentanoate as the starting material, an important intermediate of D-ring of Lycopodine5-9was synthesized in the total66.5%yield through methyl esterification, silicon protection, reduction with LiAlH4, acetonide protection, iodization, coupling with dithiane. The last two steps (desulfurization ketal and aldol condensation) are under exploration.