The Mesoporous Molecular Sieve MCM-41 Catalyzed Ferrier Reaction And The Synthesis Of Strigolactone GR24 And Its Analogues

The thesis contains two sections:Section One:2,3-Unsaturated glycosides are recognized as a kind of important building blocks in the synthesis of complicated molecules with diverse bio-activities such as sugar-containing natural products,nucleosides,oligosaccharides,glycopeptides and so on.One of the most useful strategies to obtain 2,3-unsaturated glycosides is Type ⅠFerrier rearrangement,which is similar to the allyl rearrangement.Nowadays,a variety of catalysts for Type Ⅰ Ferrier reaction have been reported.However,these catalysts more or less exist some deficiencies such as high price,complex preparation,environmental unfriendliness,etc.Therefore,it is still significant to find green and efficient catalysts for Type Ⅰ Ferrier rearrangement.In the first section of this thesis,we developed a new method for the preparation of 2,3-unsaturated glycosides by using acetyl protected glycals and different nucleophiles as starting materials via commercial available mesoporous molecular sieves MCM-41-catalyzed Ferrier Type Ⅰ reaction.The method features simple operation,easy postprocessing and nonsensitive to water or oxygen,and the catalyst,MCM-41,is stable,inexpesive,environmentally friendly and reusable.The main research includes:1)First,the influences of the solvent,the temperature and the catalyst loading on this MCM-41-catalyzed rearrangement were evaluated,and the optimal reaction condition was finalized;2)Next,different glycals were synthesized to examine the substrate scope of the new method.Under the optimal condition,3,4,6-tri-O-acetyl-D-glucal,3,4,6-tri-O-acetyl-D-galactal and 3,4-di-O-acetyl-L-rhamnal could react with different nucleophilic reagents,affording the corresponding O-glucosides,C-glycosides,and S-glucosides in good to excellent yields;3)Finally,the reuse of MCM-41 was also accomplished.Section Two:Strigolactones(SLs),which contain a fused tricyclic γ-butyrolactone,have been isolated from root exudates of various plants.SLs have several distinct biological functions and are suggested to be used for pollution-free herbicides,germination stimulants of precious herbs,regulators of plant architecture and so on.Herein,we developed a convenient and efficient approach to the synthesis of GR24,4-OH-GR24 and other novel analogs with different B or D moiety using simple benzoic acid and substituted benzoic acid as starting materials via a iron-catalyzed cascade cyclization.This strategy was short,inexpensive and convenient to fast modification of the structure,especially the 4-position of SLs.Furthermore,we also explored the enantioselective synthesis of the key structural framework of 4-OH-GR24 with the use of the chiral catalyst.The research focused on three parts:(1)The synthesis of(±)-4-OH-GR24:Firstly,(E)-4-(2-formylphenyl)-3-butenoic acid was prepared via a four-step conversion from benzoicacid.Then,a one-pot method for the construction of[6.5.5]tricycliclactone,the core structural framework of 4-OH-GR24,was developed by employing a Fe(OTf)3-catalyzed intramolecular cascade cyclization.Finally,after the introduction of the formyl group and the subsequent substitution by the bromofuranone,(1)-4-OH-GR24 and its epimer were synthesized successfully.(2)The synthesis of analogs with different B/D ring:(ⅰ)By introducing different nucleophiles into the cyclization reaction system,the installation of the tricyclic structure and the modification of C4-position of B ring in one pot were achieved.On the basis of this result,analogs with various B-ring were prepared;(ⅱ)D ring-changed analogs were also obtained by using other electrophilic reagents,such as TsCl and MsCl,instead of bromofuranone in the last step;(ⅲ)Starting from substituted benzoic acid bearing electron-withdrawing or-donating groups,the synthesis of GR24 analogs containing varied A ring were investigated.(3)We also attempted to synthesize the tricyclic lactone enantioselectively by the employment of a chiral catalyst in the cascade cyclization reaction.So far,we have gained some preliminary results that the desired lactone can be obtained with a yield of 35%and ee of 13%.