The generation of dibrominated cyclopentenones via an interrupted Nazarov cyclization is reported. The installation of two bromine atoms occurs at the α and α' positions of the cyclopentenyl scaffold via successive nucleophilic and electrophilic bromination of the 2-oxidocyclopentenyl cation and its resulting enolate. Notably, the reaction proceeds with good diastereoselectivity, favoring the symmetrical product.
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http://dx.doi.org/10.1021/acs.joc.6b02350 | DOI Listing |
J Am Chem Soc
January 2025
Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
The asymmetric and divergent total syntheses of two phragmalin (moluccensins G and H) and two khayanolide-type (krishnolide F and khayseneganin F) limonoids were disclosed, which employed a torquoselective interrupted Nazarov cyclization as the key step. Taken together with a Liebeskind-Srogl coupling, a benzoin condensation, and bidirectional acyloin rearrangements, our strategy would simplify the synthetic design of both phragmalin and khayanolide-type limonoids and facilitate their modular syntheses. Moreover, the described approach also provides additional insights into the biosynthetic relationships between these two distinct skeletons.
View Article and Find Full Text PDFNat Commun
December 2024
Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Marine cyclopianes are a family of diterpenoid with novel carbon skeleton and diverse biological activities. Herein, we report our synthetic and chemical proteomics studies of cyclopiane diterpenes which culminate in the asymmetric total synthesis of conidiogenones C, K and 12β-hydroxy conidiogenone C, and identification of Immunity-related GTPase family M protein 1 (IRGM1) as a cellular target. Our asymmetric synthesis commences from Wieland-Miescher ketone and features a sequential intramolecular Pauson-Khand reaction and gold-catalyzed Nazarov cyclization to rapidly construct the 6-5-5-5 tetracyclic skeleton.
View Article and Find Full Text PDFEuropean J Org Chem
November 2024
Department of Chemistry, University of Rochester, Rochester, NY 14627.
This manuscript describes a study of diverse reaction outcomes that stem from the ionization of -alkynyl-Prins adducts. Experimental results have demonstrated unexpected behavior in the nitrogen-containing systems compared to the analogous oxygen derivatives derived from -Prins/-Nazarov sequences. In-depth experimental studies and computational analysis revealed an intricate mechanism involving competing -Nazarov and -Nazarov pathways.
View Article and Find Full Text PDFChemistry
December 2024
Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria, 3052, Australia.
Fully substituted divinyl ketones (fsDVKs) have long been regarded as resistant to Nazarov cyclization (NC) unless they contain strategically positioned electronically activating substituents. Here, however, we show that fsDVKs bearing only electronically neutral alkyl or aryl groups actually undergo facile NC due to steric crowding in the pentadienyl cation intermediate, which raises its energy and reduces the barrier height to cyclization. Strongly ionizing and suitably bulky acid moieties further increase the energy of this intermediate cation, favoring cyclization.
View Article and Find Full Text PDFOrg Lett
September 2024
School of Chemistry, Key Laboratory of Advanced Technologies of Material, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, P. R. China.
A bioinspired total synthesis of 3--junipercedrol, which contains a strained tricyclo[5.2.2.
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