Convergent route to the purpuromycin bisphenolic spiroketal: hydrogen bonding control of spiroketalization stereochemistry

Waters, Stephen P.; Fennie, Michael W.; Kozlowski, Marisa C.

doi:10.1016/j.tetlet.2006.05.044

Cited by 34 publications

(50 citation statements)

References 23 publications

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“…Phosphonates 8 and 9 were readily synthesised by facile ring opening of γ-butyrolactone (12) or phthalide (13), respectively, with potassium hydroxide and p-methoxybenzyl choride (PMBCl) [7] followed by displacement of the resultant PMB esters 14 and 15 with lithiated dimethyl methylphosphonate (Scheme 2). For the synthesis of ester 16, bis(PMB) protection of acid 17 by using PMBCl, potassium carbonate and tetrabutylammonium iodide (TBAI) proved a more reliable method than ring opening of the corresponding lactone.…”

Section: Resultsmentioning

confidence: 99%

“…Melting points were determined with a Kofler hot-stage apparatus and are uncorrected. NMR spectra were recorded as indicated with either a Bruker Avance 300 spectrometer operating at 300 MHz for 1 H nuclei and 75 MHz for 13 C nuclei or by using a Bruker DRX-400 spectrometer operating at 400 MHz for 1 H nuclei, 100 MHz for 13 C nuclei and 162 MHz for 31 P nuclei. All chemical shifts are reported in parts per million (ppm) relative to tetramethylsilane ( 1 H) or CDCl 3 ( 1 H and 13 C).…”

Section: Methodsmentioning

confidence: 99%

“…The 1 H and 13 C NMR spectroscopic data obtained was in agreement with that reported in the literature. [13] General Procedure for the Hydrogenation/Cyclisation of Enones 37-43. Method A: The appropriate enone was taken up in tetrahydrofuran, and catalytic palladium (10 % on carbon) or palladium hydroxide (20 % on carbon) was added and the resulting reaction mixture stirred under hydrogen until the reaction was judged complete by TLC.…”

Section: 4-bis{2-[(4-methoxybenzyl)oxy]phenyl}butan-2-one (22)mentioning

confidence: 99%

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A Flexible Approach to 6,5‐Benzannulated Spiroketals

2011

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A novel route to simple 6,5‐benzannulated spiroketal analogues has been developed. A convergent Horner–Wadsworth–Emmons olefination enabled ready assembly of the spiroketal precursors. Use of a benzyl protecting group strategy enabled an efficient one‐pot hydrogenation/deprotection/spiroketalisation process to be employed providing a robust method to access a range of substituted aromatic monobenzannulated spiroketals.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: 4-bis{2-[(4-methoxybenzyl)oxy]phenyl}butan-2-one (22)mentioning

confidence: 99%

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A Flexible Approach to 6,5‐Benzannulated Spiroketals

2011

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“…The requisite dihydroxyketones are commonly assembled via iterative aldol coupling reactions [1], but other methods including Nef reactions [17,18], acetylide additions [19,20], 1,3-dipolar nitrile oxide cycloadditions [21], iterative alkylation of dithianes [22][23][24][25][26][27][28], hydrazones [29], oximes [30], nitriles [31], or dihalomethylene species [32][33][34], cross-metathesis/hydroboration/oxidation [35], iterative substitution of a xanthate [36], dihydroxylation/desymmetrization of alkenes [37], Horner-Wadsworth-Emmons olefinations [38,39], allylmetallations [40], and alkyne-alkyne cross-coupling [41] have also been reported.…”

Section: Dehydrative Spirocyclization Of a Dihydroxyketonementioning

confidence: 99%

Synthesis of 5,6- and 6,6-Spirocyclic Compounds

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2013

Synthesis of Saturated Oxygenated Heterocycles I

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“…Hydrogenolysis followed by acid-promoted ketalization of 31 led to 5,6-spiroketal 32 as a 2:1 mixture of diastereoisomers, mimicking the central portion of purpuromycin (6). [13] Scheme 7. Synthesis of 5,6-spiroketal model compound 32 according to Kozlowski and co-workers.…”

Section: Model 56-spiroketal Compoundsmentioning

confidence: 99%

Rubromycins: Structurally Intriguing, Biologically Valuable, Synthetically Challenging Antitumour Antibiotics

et al. 2007

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Although known for more than 50 years the rubromycin family still constitutes a fascinating class of antitumour antibiotics. They are characterized by a challenging molecular architecture with the central spiroketal unit as the key feature and possess highly attractive biological properties. After a short treatment of the history of their isolation, structural elucidation and biosynthesis, their biological activities will briefly be summarized. This review strongly emphasizes the synthetic efforts aimed at these complex hexacyclic spiroketals. Reactions leading to simple spiroketal model compounds are described, followed by the synthetic approaches to the fully functionalized naphthalene and isocoumarin “wings”. The coupling of these units and their transformations into more advanced spiroketals demonstrate “the state of the art” in this research field. Only Danishefsky and co‐workers have so far completed the total synthesis of a fully functionalized rubromycin derivative; however, their product heliquinomycinone (103) is still only the aglycon of the natural product heliquinomycin (7), and it was prepared as the racemic compound. All these achievements and pitfalls reveal that increased engagement of synthetic organic chemists is required to develop new methods to make rubromycins and their analogues available by a modular approach and with reasonable efficacy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Convergent route to the purpuromycin bisphenolic spiroketal: hydrogen bonding control of spiroketalization stereochemistry

Cited by 34 publications

References 23 publications

A Flexible Approach to 6,5‐Benzannulated Spiroketals

A Flexible Approach to 6,5‐Benzannulated Spiroketals

Synthesis of 5,6- and 6,6-Spirocyclic Compounds

Rubromycins: Structurally Intriguing, Biologically Valuable, Synthetically Challenging Antitumour Antibiotics

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