Hofstetter, Elena (2022). Enantioselective Hydroalkylation and Natural Product Modification Mediated by Radical Reactions. (Thesis). Universität Bern, Bern
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22hofstetter_e.pdf - Thesis Available under License Creative Commons: Attribution-Noncommercial-No Derivative Works (CC-BY-NC-ND 4.0). Download (58MB) | Preview |
Abstract
The enantioselective hydroalkylation of prochiral alkenes employing catalytic amount of chiral thiols was investigated. The transition metal-free process, using Et3B and air as radical initiator and H2O for catalyst regeneration, is an easy, cheap and eco-friendly way to perform this transformation under mild conditions. Cysteine-based peptides showed high enantioselectivity ratios for the haydroalkylation of 1,3-oxazolidin-2-one derivatives delivering the desired products in high yields. The investigation of a chiral system compatible with the linear pro-chiral alkenes is still on-going. Additionally, we performed the modification of highy oxygenated forskolin via intermolecular carbon-centered radical addition to the vinyl moiety. Two less functionalized model substrates sharing the same polycyclic skeleton - manoyl oxide and its 13-epimer - were as well investigated. Highly regio- and reasonably stereoselective iodine atom transfer radical addition (ATRA) reactions were developed. The formation of tetracyclic ether derivative and in situ protection of the forskolin 1,3-diol moiety as a cyclic boronic ester were reported. Furthermore, we took advantage of manoyl oxide and epi-manoyl oxide structure conformation and investigated the remote long range 1,5-hydrogen atom transfer. This concept is know as ”billiard reaction” or ”travelling radical”. Remote C-H functionalization of labdane diterpenoids via iodine atom transfer radical addition and further functionalization was reported.
| Item Type: | Thesis |
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| Dissertation Type: | Single |
| Date of Defense: | 21 October 2022 |
| Subjects: | 500 Science > 540 Chemistry |
| Institute / Center: | 08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP) |
| Depositing User: | Hammer Igor |
| Date Deposited: | 15 Nov 2022 16:53 |
| Last Modified: | 16 Nov 2022 01:30 |
| URI: | https://boristheses.unibe.ch/id/eprint/3916 |
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