Jonathan H. George
University of Adelaide
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Publication
Featured researches published by Jonathan H. George.
Organic Letters | 2010
Jonathan H. George; Jack E. Baldwin; Robert M. Adlington
A biosynthetically inspired synthesis of (+)-liphagal has been achieved from (+)-sclareolide in 13 steps (9% overall yield). The key step is a biomimetic ring expansion of a highly stabilized benzylic carbocation, which generates the seven-membered ring and the benzofuran of the natural product in a single cascade reaction.
Organic Letters | 2010
Jonathan H. George; Micha D. Hesse; Jack E. Baldwin; Robert M. Adlington
Biomimetic syntheses of three polycylic polyprenylated acylphloroglucinol natural products isolated from Hypericum papuanum, ialibinone A, ialibinone B, and hyperguinone B, have been accomplished by selective oxidative cyclizations of the proposed biosynthetic precursor 5, which was synthesized from phloroglucinol in three steps.
Organic Letters | 2011
Justin T. J. Spence; Jonathan H. George
A structure revision for the recently isolated fungal meroterpenoids, cytosporolides A-C, is suggested based on biosynthetic speculation and reinterpretation of existing spectroscopic data. The structure revision is supported by a biomimetic synthetic study, featuring a [4 + 2] cycloaddition reaction between a presumed o-quinone methide intermediate and β-caryophyllene.
Organic Letters | 2012
Henry P. Pepper; Hiu C. Lam; Witold M. Bloch; Jonathan H. George
The polycyclic polyprenylated acylphloroglucinol natural product garcibracteatone has been synthesized in four steps from phloroglucinol, using a strategy based on biosynthetic speculation. The key biomimetic transformation is a cascade of 7-endo-trig and 5-exo-trig radical cyclizations followed by a terminating aromatic substitution reaction.
Organic Letters | 2009
Karl J. Hale; Soraya Manaviazar; Jonathan H. George; Marcus Walters; Stephen M. Dalby
Asymmetric total syntheses of (+)-azinothricin and (+)-kettapeptin have been completed through a common new pathway that exploits a highly chemoselective coupling reaction between the fully elaborated cyclodepsipeptide 5 and the glycal activated esters 3 and 4 at the final stages of both respective syntheses.
Organic Letters | 2013
Justin T. J. Spence; Jonathan H. George
The total synthesis of ent-penilactone A and penilactone B has been achieved via biomimetic Michael reactions between tetronic acids and o-quinone methides. A five-component cascade reaction between a tetronic acid, formaldehyde, and a resorcinol derivative that generates four carbon-carbon bonds, one carbon-oxygen bond, and two stereocenters in a one-pot synthesis of penilactone A is also reported.
Organic Letters | 2015
Adrian W. Markwell-Heys; K. Kuan; Jonathan H. George
The structure of siphonodictyal B has been reassigned on the basis of the total synthesis of both possible C-8 epimers. The revised structure of siphonodictyal B was converted into liphagal by acid catalyzed rearrangement of a proposed epoxide intermediate. This biomimetic cascade features a succession of four distinct reactions (epoxidation, o-quinone methide formation, ring expansion, and benzofuran formation) that occur in a one-pot operation under mild conditions. During these studies we also isolated a surprisingly stable o-quinone methide that supports our mechanistic proposal for liphagal biosynthesis.
Angewandte Chemie | 2016
Hiu C. Lam; Justin T. J. Spence; Jonathan H. George
Hyperjapones A-E and hyperjaponols A-C are complex natural products of mixed aromatic polyketide and terpene biosynthetic origin that have recently been isolated from Hypericum japonicum. We have synthesized hyperjapones A-E using a biomimetic, oxidative hetero-Diels-Alder reaction to couple together dearomatized acylphloroglucinol and cyclic terpene natural products. Hyperjapone A is proposed to be the biosynthetic precursor of hyperjaponol C through a sequence of: 1) epoxidation; 2) acid-catalyzed epoxide ring-opening; and 3) a concerted, asynchronous alkene cyclization and 1,2-alkyl shift of a tertiary carbocation. Chemical mimicry of this proposed biosynthetic sequence allowed a concise total synthesis of hyperjaponol C to be completed in which six carbon-carbon bonds, six stereocenters, and three rings were constructed in just four steps.
Organic Letters | 2012
Henry P. Pepper; K. Kuan; Jonathan H. George
A hypothesis for the biosynthesis of the frondosins A-E is presented. Synthesis of a liphagal-frondosin C hybrid molecule has been achieved, with the frondosin C 6-7-5-6 ring system being constructed by a photochemical process that follows an intramolecular Paternò-Büchi reaction/fragmentation pathway.
Chemical Communications | 2010
Karl J. Hale; Soraya Manaviazar; Jonathan H. George
Herein we describe our asymmetric total syntheses of (+)-A83586C, (+)-kettapeptin and (+)-azinothricin. We also demonstrate that molecules of this class powerfully inhibit beta-catenin/TCF4- and E2F-mediated gene transcription within malignant human colon cancer cells at low drug concentrations.