scholarly journals Investigations of Ring-Opening Reactions of Cyclopropanated Carbohydrates: Towards the Synthesis of the Natural Product (--)-TAN-2483B

2021 ◽  
Author(s):  
◽  
Russell James Hewitt
Keyword(s):  
Natural Product ◽  
Ring Opening ◽  
Cyclopropane Ring ◽  
Ring Expansion ◽  
Ring Opening Reactions ◽  
The Subject ◽  
The Many

<p>Cyclopropanes and carbohydrates are materials of great interest to chemists. Ring opening reactions of cyclopropanated carbohydrates have excellent potential for synthesis, due to the many diverse structures that may be obtained. The work described in this thesis explores the scope of such ring opening reactions, and extends to the synthesis and reactions of several novel cyclopropanated carbohydrates, in which synthesis of a natural product was also investigated. Several bicyclic gem-dihalocyclopropanes, including 97, were synthesised. Base-mediated cyclopropane ring opening of 97 in the presence of nucleophiles afforded a series of 2-C-branched glycosides 389 and 390 (Chapter 2), whereas silver-promoted ring expansion provided access to seven-membered rings (255 and 256) (Chapter 3). Studies on the mechanisms of the ring opening processes were also carried out. Ring-opening reactions of carbohydrate-derived gem-dihalocyclopropanes were also applied to the exploration of possible routes to the natural product (--)-TAN-2483B (154). Attempts to convert d-galactose and d-xylose into the dihydropyran 193 are the subject of Chapter 4, while the transformation of d-mannose into 193 and subsequent efforts to prepare the natural product 154 are discussed in Chapter 5.</p>

scholarly journals Investigations of Ring-Opening Reactions of Cyclopropanated Carbohydrates: Towards the Synthesis of the Natural Product (--)-TAN-2483B

2021 ◽  
Author(s):  
◽  
Russell James Hewitt
Keyword(s):  
Natural Product ◽  
Ring Opening ◽  
Cyclopropane Ring ◽  
Ring Expansion ◽  
Ring Opening Reactions ◽  
The Subject ◽  
The Many

<p>Cyclopropanes and carbohydrates are materials of great interest to chemists. Ring opening reactions of cyclopropanated carbohydrates have excellent potential for synthesis, due to the many diverse structures that may be obtained. The work described in this thesis explores the scope of such ring opening reactions, and extends to the synthesis and reactions of several novel cyclopropanated carbohydrates, in which synthesis of a natural product was also investigated. Several bicyclic gem-dihalocyclopropanes, including 97, were synthesised. Base-mediated cyclopropane ring opening of 97 in the presence of nucleophiles afforded a series of 2-C-branched glycosides 389 and 390 (Chapter 2), whereas silver-promoted ring expansion provided access to seven-membered rings (255 and 256) (Chapter 3). Studies on the mechanisms of the ring opening processes were also carried out. Ring-opening reactions of carbohydrate-derived gem-dihalocyclopropanes were also applied to the exploration of possible routes to the natural product (--)-TAN-2483B (154). Attempts to convert d-galactose and d-xylose into the dihydropyran 193 are the subject of Chapter 4, while the transformation of d-mannose into 193 and subsequent efforts to prepare the natural product 154 are discussed in Chapter 5.</p>

Formation and reductive ring opening reactions of indolyl bicyclic-isoxazolidines-II:7 access to novel natural product analogs

2016 ◽  
Vol 57 (42) ◽  
pp. 4688-4692 ◽  
Author(s):  
Gagandeep Singh ◽  
Tilak Raj ◽  
Vivek Gupta ◽  
Mohan Paul Singh Ishar
Keyword(s):  
Natural Product ◽  
Ring Opening ◽  
Ring Opening Reactions

scholarly journals Synthesis of Highly Functionalised Furo[3,4-b]pyrans: Towards the Fungal Metabolite (−)-TAN-2483B

2021 ◽  
Author(s):  
◽  
R.M. Kalpani K. Somarathne
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Natural Product ◽  
Cyclopropane Ring ◽  
Ring Expansion ◽  
Ethyl Esters ◽  
Pyran Ring ◽  
Synthetic Strategy ◽  
Alternative Approach ◽  
Synthetic Approaches

<p>Carbohydrate-derived cyclopropanes combine both the stereochemical wealth of carbohydrates and the reactivity of cyclopropanes. A diverse variety of reaction modes for these cyclopropyl carbohydrates can be harnessed for the synthesis of natural products and other targets.  The natural products (−)-TAN-2483A and (−)-TAN-2483B are fungal secondary metabolites displaying a variety of bioactivities such as inhibition of c-src kinase action and parathyroid hormone-induced bone resorption. This thesis described several synthetic approaches to the natural product (−)-TAN-2483B and analogues of (−)-TAN-2483B employing cyclopropane ring expansion.  The synthetic route to (−)-TAN-2483B began with the readily available substrate D-mannose. The pyran ring unsaturation of the natural product was established by a cyclopropanation-ring expansion sequence. A synthetic strategy via dichlorocyclopropane-based intermediates is described in chapter 2. This being unsuccessful, an alternative approach via 2-fomyl-glycal was developed in chapter 3. The chapter 2 and 3 provided a solid background for the achievement of the analogues synthesis illustrated in chapter 4 via dibromocyclopropane. Lewis acid-mediated alkynylation followed by Pdcatalysed carbonylative lactonisation was successfully utilised in the revelation of the furo[3,4-b]pyran ring skeleton. This route afforded analogues of TAN-2483B; the Z-and E-unsaturated ethyl esters 140 and 141 and hydroxy(−)-TAN-2483B 145. The total synthesis of (−)-TAN-2483B was not achieved due to unforeseen obstacles encountered in the deoxygenation of the side arm of 335 (Chapter 4) into the E-propenyl side arm of (−)-TAN-2483B.</p>

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