Asymmetric Total Syntheses Of Dihydropyones Obolactone, Sesquiterpenes Heliannuols B And D

This dissertation aims aims at the studies on the asymmetric total syntheses of dihydropyrone obolactone, sesquiterpenes heliannuols B and D. Some reactions at room temperature ionic liquid, syntheses of some chiral ligands and the applications in asymmetric catalysis are also studied. It consisted of the following five parts:Chapter 1. The construction of chiral dihydropyrone rings and the applications in natural products syntheses (review)The review introduced the methods of construction of chiralγ,βandα-dihydropyrone rings in natural products syntheses.Chapter 2. The first asymmetric total synthesis of obolactone.The work of our group in synthesis of dihydropyrone natural products was introduced briefly.The first concise and efficient asymmetric total synthesis of dihydropyrone natural product obolactone has been achieved using Brown's enantioselective allylation reactions and ring closing metathesis reaction as the key steps. Both the stereocenters were established facilely and high selectively, and theα-pyrone andγ-pyrone rings were constructed easily with this strategy. The synthesis consists of 11 steps starting from commercially available 3-(OTBS)-propionaldehyde in 15% overall yield.Chapter 3. Asymmetric syntheses of heliannuols B and DThe works of our group in syntheses of heliannuol series natural products were introduced briefly.Some synthetic strategies to synthesize heliannuol D have been tested. Asymmetric syntheses of the sesquiterpenes heliannuols B and D have been accomplished with a common strategy using Mitsunobu reaction and ring-closing metathesis as the key steps, in which heliannuol B was synthesized for the first time. Chapter 4. Reaction in room temperature ionic liquidThe advantages of RTIL and the works of our group in this field were introduced briefly.The [3, 3] oxo-rearrangements were performed in an ionic liquid [BMIm]BF₄ using Pd(OAC)₂ as catalyst in the presence of PPh₃. The reaction is efficient and could be conducted under mild conditions.Chapter 5. The syntheses of chiral ligands and their applications in asymmetric catalysisThe works of our group in the fields of syntheses of chiral ligands and their applications in asymmetric catalysis were introduced briefly.The multident ligands derived from camphor were synthesized and applied in catalysis of the asymmetric addition of diethyl zinc to aldehydes.The applications of [3, 3']-difunctional BINOL in asymmetric catalysis were introduced briefly.[3, 3']-Bis(2-pyridyl)-BINOL was synthesized and applied in catalysis of some asymmetric reactions.